The LED's Challenge to High Pressure Sodium

The LED's Challenge to High Pressure Sodium

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In my last video we talked about the high pressure sodium lamp and its ubiquitous, use in outdoor lighting already, this type of lighting is starting to be phased out with various, technologies, with new LED technology among, the most common, now, given the robust nature of the sodium lamp and its proven track record in providing an efficient light source reliably, does, it make sense that we switched to newer light sources well. As usual in life there, are pros and cons so, let's start with a basic question why, do we use outdoor, lighting for, street lighting specifically. The basic answer is to improve safety particularly, pedestrian. Safety, the, odds of a crash of any kind are greater at night because it's harder to see with, the aid of artificial, roadway lighting a driver, can see much farther than their cars headlights shine especially, to the sides now, of course there are disadvantages, to large amounts of street lighting which we'll get to but, assuming safety, is the goal our sodium lamps good well, no, not, really remember, how I said that the sodium d-line is close to our eyes peak sensitivity but, only under photopic, daylight, conditions well. It turns out that our eyes see quite differently at night than during the day under. Night time schoo topic lighting conditions, our eyes actually see bluish light better and that, makes sense after all moonlight, and Starlight are pretty blueish so under these dimly lit conditions having, a greater sensitivity to, blue light would, mean we can see better, underscore. Topic lighting conditions, only the rod cells in our eyes are activated, rod, cells cannot distinguish, color but they are much more sensitive to light than the cone cells the, peak sensitivity of the rod cells is around 498. Nanometers, which, is a green blue color now. Of course under street lighting our cone cells are still active we can after all see colors and are not exclusively, using the rod cells this, dim but not quite dark lightning scenario, is often called mosaic vision, a mix, of the two still. Stimulation. To the rod cells will be far more visible and is more important, so, then how well does the light from sodium vapour lamps line up with our school topic light sensitivity, not, well this, is the CIE 1951. S go topic luminosity, function graph the, x-axis. Is the wavelength of light in nanometers and the y-axis is the eyes relative, sensitivity to these wavelengths under school topic nighttime conditions as you, can see peak sensitivity is around the 500 nanometer mark and where's, the wavelength produced by a sodium vapour discharge it's. About here 589. Nanometers the. Rod cells are barely activated, by a sodium discharge, while, the discharge may be extremely. Efficient at producing visible, light at night, time this light is fundamentally, misaligned with, our eyes sensitivity. See if you look at the response curves of schoo topic and photopic conditions, together you can see that the sodium discharge, lines up great with our photopic, vision but. When our eyes are adjusted, to nighttime lighting, conditions it's actually, pretty bad this, is why focusing, on the sodium d-line emissions seemingly perfect alignment with our vision is somewhat. Of a farce, while, it's true during the day it's, literally, quite far from the truth at night aside, from the simple spectral misalignment. Of the sodium lamp research, shows that people can indeed to see better under light sources with a bluer spectral, content in peter, moran tazed research for the lighting Research Center at the Rensselaer Polytechnic Institute, linked. Below survey, respondents, strongly, preferred the light from a 6,500, K correlated, color temperature, light source over that, of high-pressure sodium with, metrics of visibility, brightness, safety, and security color, rendering and overall, preference, all favoring, the newer light source which, also used only 55%, of the energy of the high-pressure sodium lamps it replaced the.

Study Which by the way is really comprehensive, and worth taking a look at was done in 2008, which was a tad before LED technology became, economically viable the. Study compared induction, lighting which is sort of like fluorescent lighting and worth a video on its own one day because it's pretty neat if not so practical any longer as well, as metal halide lighting to the sodium lamps for the purpose of creating a recommendation to a local utility, company, the. Conclusion, was that metal halide didn't make sense due to higher maintenance costs, but, induction, would make tons of sense but, I also liked this final recommendation, white. Light emitting diodes should be considered as replacements, for HPS street lighting in about three years time when, their efficacy is higher and their cost has reached reasonable, levels to be economically, viable growing. Utilities, may want to consider postponing decisions. On street light replacements, until, white LEDs become economically, available well, it's been about ten years since that study and LEDs, are economically. Viable in fact, they've become in, right oblique anomic, Lee viable but, before we move on to them let's go over the main issue once more because. Of the spectral, misalignment. Of the sodium vapour lamp with our school topic and Mesaba Clyde sensitivity, it takes, more light output, from a sodium lamp to produce the same visible, light level from, a bluer light source, in fact dr. Alan Lewis of the New England College of Optometry measured. Individual's, response time to a hazard approaching from the sides and found, that in well-lit areas such as a major motorway, a high-pressure sodium light system needs to produce 3.9, times as much light as a metal, halide source, to achieve the same response time the. Effect is even greater in dimly lit areas where, he found that 7.8. Times as much light from high-pressure sodium was required to match response, time under cooler metal, halide light sources so it seems as though the high-pressure sodium light is less efficient, than it appears on paper and that roadways safety is greatly increased when light sources are used that are tuned to our schoo topic and mazovick light sensitivity, it's. Looking pretty bad for high pressure sodium but. There's one thing that HPS, technology, doesn't do that bluer light sources might that, my friends is circadian rhythm, disruption, research. Has suggested that the color of light we are exposed, to has a great impact on what time our biological clocks, think it is the. Shorter wavelength of daylight Sun and blue sky may, help keep us awake by suppressing melatonin production, and, the long wavelength, light of the sunset may, signal our bodies to sleep by allowing melatonin, to seep into our blood streams to. Help us understand, the impact different light sources can have on circadian rhythm disruption light. Sources are characterized, by their melon optic content, there's, a great source from the US Department of Energy linked down below which goes over this in much greater detail, but as a general overview with, high pressure sodium technology, normalized, at one for both schoo topic light content, and Mellon optic light content a metal, halide lamp with a color temperature of about 4,000, K will, have about 2.5, to 2.8, times as much schoo topic light content, but, also produces, 3.16. 23.7. Five times as much melon topic light content, if, you look at the various color temperatures, of LED light sources you, can see that as the color temperature increases, both, schoo topic light content, and melon, Opik light content, increase however.

Melon, Topic light content increases at a greater rate than schoo topic light what this means is there's a trade-off and it's, complicated. The, higher the color temperature the more scotopic, light it produces which means you could use less light and thus less energy so you get the same perceived brightness and safety levels but, because. Melon Opik light content, increases at a greater rate although, you may need less light of, a higher color temperature, it will disrupt circadian, rhythm, to a greater extent you. Can see that high-pressure sodium has among the lowest melon, Opik light content, of any light source with, only amber leds and low pressure sodium producing. Less melon Opik light so, then we're presented, with a choice we. Can clearly use less energy and expect, a safer, nighttime driving experience, with light sources of higher color temperatures, but. This may cause unwanted, side effects that sodium lighting largely, doesn't and this, is completely, ignoring aesthetic, preferences, I myself, generally. Detest, cooler lighting as I find it hard and unpleasant but I can't acknowledge its safety advantages, in my area, and interstate, 88 many, of the roadway lights have been changed, from high pressure sodium to LED the. Change is dramatic with, visibility greatly. Enhanced, once under the cooler light as much. As I don't like the color I can tell that it's a lot safer, visibility. In my periphery is tremendously, better and I'm certain, these new lights are using less energy than those they replaced before I move into the conclusion of this video let's discuss the issue of light pollution light. Pollution is exactly what it sounds like excess. Light in our environment, that is irritating, unnecessary, poorly, distributed or in general unwanted. Outdoor. Lighting is by far the most prolific, source of light pollution and it has gotten so bad that people living anywhere near a city can barely, see the night sky, there's, even an anecdote, about a widespread blackout, in Los Angeles causing, many panicked, 911. Lifelong. Residents, who had never seen the Milky Way before and were a little scared of it light pollution is a complicated, problem but the LED may actually help to solve it now, to be clear the solutions I'm about to offer aren't exclusive, to LEDs but the way light is emitted from an LED chip makes, controlling it relatively, easy, so, first let's discuss one of the biggest causes of light pollution lights. That point up this. Is less obvious than it seems but it's in important, right, outside my apartment are, dropped lens Cobra luminaires containing, high-pressure sodium lights because. The lens protrudes, downward. From the fixture a lot, of light escapes to the sides and indeed upwards, I'm, on the fourth floor of my building and my eye level is above these street lights but, I can still see the source of the light this. Is not ideal for a number of reasons first, a lot of light is being wasted by lighting up things that are not, the road that's, kind of dumb but secondly.

A Lot of this light is going up into the sky granted. This style of fixture isn't the worst offender, but a better design would be a flat lens that does not allow light to escape above, the horizontal. This. May still throw light farther to the sides than necessary, but, none of it will end up lighting the sky the. Worst offenders, for this kind of light pollution are lights that illuminate buildings. By shining upwards, wall, pack lights without shielding, and these, decorative, fixtures, I'll admit they're pretty but, they're really wasteful, recently. I was on an airplane flying, into Chicago, at night I took some videos as we landed, and you can see the difference between a well-managed, light and a poorly managed light this, roadway is lit well I cannot, see the actual light sources I can only see the reflected, light from the road that's. What we want as we, got closer to the airport these, neighborhoods, had tons, of lights that were visible from above much. Of the light produced by these lamps is shining into the sky and being wasted, I should. Not be able to see the actual light source from an airplane yet. I can this. Is contributing, to sky glow sky, glow is what makes the night sky hard to see when you're close to a city this, is probably the most widespread light, pollution problem, and while it's not caused exclusively. By poorly designed fixtures, they, are a major component but. Once again the, solutions, the sky glow are complicated. Largely. Because light sources that cause the least amount of sky glow are, high and low pressure sodium in fact. Low pressure sodium is used widely around large astronomical, observatories, because they're nearly monochromatic, light, output can easily be filtered out eliminating. Any sky glow they create I saw. A large number of people saying that high-pressure sodium can also be filtered out but, I don't think that's true due to the pressure broadening and their spiky or output, someone. Correct me if I'm wrong but I could only find references, to low pressure sodium being used around observatories. Anyway. Where it gets tricky is that an LED light source has about three times as much sky glow impact, than a high-pressure sodium light but. Also you need less of it so perhaps the sky glow impact is similar, in, addition, the sky glow impact of incandescent lighting is barely higher than low pressure sodium so. It could be that led street lighting correlated, to a 2700. K color temperature, causes less sky glow than high-pressure sodium but. I think further research needs to be done there in any case what makes LEDs potentially, much better at reducing sky, glow is the optical, systems that can be combined with them early. LED fixtures may have used a large number of small 1 watt LEDs, and tiny, lenses to direct their light some. Really bad designs may have simply had an exposed, chip providing, little directional, control you, still see this a lot in cheap floodlight fixtures, but, newer fixtures, like these from Cree will use large chip onboard admit errs like these 10 watt chips but larger and because, they only emit light in one direction it's very easy to control their output with a lens you can see on the spec sheet that there are five lenses in total the larger fixtures have more most. Importantly, the optic system is customizable, depending. On fixture height and spacing you may need a wider spread of light or a shorter one due. To the customizable. Optics you can get wonderfully, consistent, lighting on a road surface such as this area here this, may also help prevent light pollution because, less overall light is needed the, hot spots of Lights you see from above here I mean some areas get too much light and others get too little a Morse, code Opik light source with better and more consistent control, may, not only reduce light pollution but. May use less energy and provides safer driving now many of these developments, are rather new especially the newer optic designs but, the advantages, of LED lighting become confused, when drop-in, replacement, bulbs are used I don't, have any major issues about going this route after, all replacing, the entire fixture, can be costly and some, drop-in designs are fairly good but, the optic, system of a sodium mercury, vapor or metal halide fixture, is designed, to reflect and project light emanating, from a tiny arc tube which, an LED drop-in can't recreate. Many of the complaints regarding poor light distribution and LED replacement lamps may simply be from the use of these replacements. Then. There's the issue with existing ballasts. Some, drop in lamps claim to work with existing ballasts, but I have a few misgivings, regarding how, well their power supplies deal with the voltage the ballast provides, particularly.

If The high voltage igniter sends, some crazy voltage, spikes to the LED dropping I'm, sure they can be designed to cope but, it still worries me someone so then we have a series of complicated, choices to make Soniya, vapor lights are pretty efficient have only a moderate contribution, to sky glow caused, only minor circadian. Rhythm disruption if any and have a proven track record of reliability, but. Their color also makes them far less effective. At improving safety, and due, to the misalignment, of their output with our scope topic light sensitivity, they require more light and thus use a lot more energy than a wider light source perhaps. Less an issue but still important is that they contain both mercury. And elemental, sodium meaning. Their disposal, is far more dangerous and complicated if we were to switch to a white LED source with a color temperature of about 5,000, K nighttime. Visibility would, be greatly increased, studies. Have shown that people see hazards, far sooner under this light and as the bluer wavelengths, match our schoo topic and mess up at color sensitivity more closely we, can use less of it while also achieving a greater safety benefit this, reduces, the need for energy, however. This bluer light contributes, more to circadian, rhythm disruption and, sky glow but some of that is mitigated, by the lower output required, by these light sources still. Many, people may not find the aesthetics, of this light source pleasing, one. Possible, compromise would be to use a warmer, color temperature, LED light source data. From the US Department of Energy tells us that a 3000, K LED, light would produce 1.89, to two point three nine times as much go topic light as a high pressure sodium lamp while increasing, Mellon optic content between two point one and two point nine nine times, because. Of its greatest go topic output a 3,000, K LED replacement should, only need to produce about half as much light as a high-pressure sodium lamp this. Effectively, cuts the circadian rhythm disruption potential. In half to placing. It near about the same as high-pressure sodium the, greatest downside, to using a warm color temperature, LED is in their efficiency, the, efficiency of. These lights is very similar to that of an average high pressure sodium lamp at 67. Lumens per watt these 3000, K LEDs are just slightly less efficient, than the sodium lamp featured in my last video although. You would need only about half as much light output, there are high pressure sodium lamps, which approach 150. Lumens per watt this. Would mean that a 3000, K LED will use just about as much energy as a very, efficient, high pressure sodium lamp I'd, still call that good but it makes replacement, less compelling, to. Normalize the effects of scotopic light content, I've multiplied, the lumens per watt number by this Co topic light content, for the following light sources as you, can see the normalized, efficiency, of the LED goes up considerably as the color temperature does due, to both luminous, efficiency and greater scotopic content, this, is likely why most LED street lamp installations, are done with the bluish 50 700 K and higher color temperatures, you. Can use the least amount of energy to produce the same amount of perceived brightness and safety, however. The normalized, efficiency, of even the 3000, k LED is very similar to that of high-pressure sodium and few, HPS lamps actually output 150. Lumens per watt also. The calculated, lumens per watt of the LED is based on the input power of the fixture so, the losses in the ballast which are fairly high for high pressure sodium aren't, accounted for here to conclude although the high pressure sodium light is very efficient, its primary, output color is misaligned, with our nighttime visibility only. About a quarter of its light is actually effective, at stimulating the, cells in our eyes although. The cool color temperature, of many LED replacements, is harsh and aesthetically, displeasing studies. Have shown that it is not only more efficient, but also makes driving at night safer, there. Is however the potential for greater circadian rhythm disruption and larger amounts of sky glow using these bluer light sources, still. It seems clear that the high pressure sodium lamp is on its way out, advancements.

In LED technology are, happening at a breakneck pace just. 10 years ago they weren't seen as viable but, today even the least efficient, of LED replacements, ends, up meeting the efficiency, of high pressure sodium when, schoo topic light output is considered, as it. Stands in 2018, we are faced with the choice of efficiency, over aesthetics, I'm, pretty, sure I'd enjoy roadways lit with relatively, warm 3000k, LEDs and these, also wouldn't disrupt sleep much but, you can save a lot more energy and potentially, have safer roadways with, 5700. K lighting either. Way it seems clear that LED technology will, very soon overtake, the tried-and-true high pressure sodium lamp just, as the HP s lamp itself replaced, the mercury vapour lamp and in, 40 or 50 years who, knows what technology, might light our roadways. So. I have a couple of things to close out first you may have noticed in my chart that the mercury vapor lamp had a normalized efficiency, of over 100 lumens per watt and the, 50 watt sodium lamp in the last video was only 78 lumens, per watt mercury. Vapor bulbs do have considerable, operating, disadvantages, compared to high pressure sodium most, notably their steady decrease in light output as they age but, I think it is somewhat humorous that our current understanding of, the visual system suggests. That sodium light may have been a step backwards, in some situations, you may have noticed that I didn't talk about the blue light from LEDs and how this is supposedly ruining, our eyes that's. Because the science. Behind this is questionable, at best you. Can clearly see in this chart that there is blue light content, and nearly all light sources and lower, color temperature, LEDs have less blue light content, than their higher color temperature, varieties, I don't. Doubt that blue light can disrupt circadian rhythm that much seems certain but, considering that our eyes can withstand the intensity of sunlight, which is far, far greater than any normal artificial, light source and also has a lot of blue light and ultraviolet. Which definitely is harmful I think, the blue light thing is just fear-mongering if someone. Can point to some verified, peer-reviewed, research supporting, this and not a dodgy website, I'll consider changing my stance in any, case the high flexibility. Of LED technology means, that it can be tuned in pretty much any way you'd like I also want to give a shout-out to V Westlife for the suggestion, of LED fixtures with both high and low color temperatures, that, will switch to the warm light later in the night I think, that's a great idea though. Obviously it would add expense to any fixture however. I was surprised to learn that the cree LED fixtures, i've been using as a reference are, all capable of dimming and they have a 0 to 10 volt control input to enable this reducing. Light levels to perhaps 50% of normal after midnight might become a common practice and i think that would be pretty wise maybe. This will get combined with technology similar to Philips warm glow and we'll get incandescent, like lightning at night for, those worried about light pollution for astronomical observatories. There are amber, LED streetlights available designed to replace low pressure sodium lights this, is also great news for wildlife many, animals cannot see the wavelength of light produced by low pressure sodium so, this light source is used where lights may be disruptive, one, particular, example is near beaches where sea turtles lay their eggs after. They hatch baby sea turtles follow moonlight, to the ocean and street, lighting was confusing, the poor things and they were travelling inland since. They cannot see the wavelength of a low pressure sodium light or its amber LED equivalent, they, aren't confused and successfully. Make it to the ocean where they belong as a last little tidbit the spec sheet from Cree says that their LED cobrahead replacements, should produce at least 95, percent of, their original light output, after a hundred, thousand, hours assuming. The driver and heatsink are robust enough these fixtures should last well beyond twenty years that. Is impressive, thanks, for watching I hope you enjoyed the video if you haven't subscribed, to technology, connections, yet and you like my nerdy deep dives into whatever floats through my head what, are you waiting for hit the button please, as. Always thanks, to everyone who supports this channel on patreon, you are all making a big difference and it's super awesome of you if you're, thinking of joining these awesome people and becoming a patron yourself why, not check out my patreon page thanks. For your consideration and I'll see you next time.


2018-06-20 13:22

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I feel like street lights that interfere with circadian rhythms, especially on long drives and with the controlled projection like you talk about would be *good* for safety.

Joey Riso oh you want your circadian rythm to be disrupted? So you can have an accident during the day? The one you are expressing is a dangerous idea in my opinion.

Oddly enough, as somebody who lives near 2 street lamps that recently switched from HPS to LED, the amount of light bleed through my windows is *greatly* decreased compared to before, though that likely has to do with the fact that the LED-based lights have rectangular lenses that throw the light along the road, with very little bleed past the sidewalk, there is *some* light, but its such a small amount that it is easily blocked by the blinds. Also, some of the LED street lights in my area (in areas without a lot of traffic) actually turn off when there is no motion for a certain amount of time. (not ideal for heavy traffic areas, but quite nice for housing areas)

Rainer Riegler do you know of curtains that automatically open when the sun comes up?


It's good for safety. It's bad once you get home and want to go to sleep and can't because your body is still in daytime awake mode. Pick your poison ☠

Kris M is correct. Circadian rhythm disruption is far more than just keeping people awake while driving, it can cause fairly serious effects. Circadian rhythms are basically your body's "internal clock." What time you wake up, when you get hungry, when your body is ready for peak physical activity, and when you want to go to sleep. It also helps manage things like your body temperature and various hormones. Circadian rhythm disruption is what makes it miserable for morning people to work the night shift. Their appetite and activity levels are affected, they constantly feel worn-out and sluggish, and their quality of sleep suffers because their brain thinks they should be awake during the times they have to sleep. Circadian rhythms are also a big part of why jet lag happens, and why it takes a couple of weeks for your body to adjust if you've traveled a long distance. It needs to readjust to the new time zone, using cues from sunlight and moonlight to figure out when you're supposed to be awake. Circadian rhythm disruption can also result from solitary confinement and lack of exposure to natural light, i.e. people who work in a basement all day or live in certain latitudes or climates. I have had a circadian rhythm issue since birth called delayed sleep phase disorder. My sleep / wake cycle is delayed by several hours, so I go to sleep between 5-7 AM and wake between noon and 2 PM. It wasn't diagnosed until I was 19. Even though I was awake all day, I often couldn't fall asleep until 2 or 3 (or later) in the morning, meaning I was chronically sleep deprived in my childhood. That may have affected my long-term memory. It definitely affected my school performance, my relationships with others, and my mental state. *TL;DR* Circadian rhythm disruption is a longer-term thing that can cause physical issues by throwing off your body clock, and can also be harmful to mental state. It should not be taken "lightly," so to speak.

I don't think that you'd even have to be living near a road to be adversely affected by widespread use of highly melanopic road lighting. Even if appropriate lighting fixtures were used, this melanopic light will still contribute to light pollution. This melanopic light will then be reflected/scattered off the sky and clouds to residents all around the city. With enough light pollution from this kind of light, the entire night sky will have a bluish glow, even for those at a distance from the roadways that light originated from.

Keeping you more awake while driving at night is good, but circadian rhythm disruption is bad, they are not one and the same thing. The former causes the latter if it is a regular occurance.Working in shifts is another possible cause of CR disruption. The circadian rhythm disruption involves lowering your quality of sleep, causing a general reduction in alertness while being awake. As a tertiary result, you become a worse driver in general.

I seriously doubt many municipalities are going to be changing their lights anytime soon, unless the drop in replacement costs the same as a new lightbulb. All of the big cities have finances that are unreal. The feds might change the lights on the interstates that run through large cities, but I seriously doubt that they are going to spend the money to swap these out. I would have to think the municipalities are paying flat fees for power tied to a contract. There is lots of excess electricity at night anyway. It is difficult to overstate just how bad most of the big cities are. If they had to use GAAP standards, most would be insolvent and would need to declare bankruptcy. A lot of the states are in similar shape to the munis. The cost of doing this has likely played a role in the fact that most places have not done this yet.

+Emmett Wainwright Indeed, the other thing about keeping it to being mostly quiet residential streets only have a 20 mph limit anyway at that speed there is a lot more time to react even if reaction time is a little slower with the HPS lamps and the consequences are far lower even most pedestrians survive at those speeds (particularly adults and children tend not to be on the streets at night so much). City centre areas are worse as it's far more common to have 30 mph roads that have significant foot traffic 24/7, doesn't help that planners are not exactly smart with some things (Who's genius idea it was to approve an alcohol licence for a bar located literally on the A38 Aston Expressway in Birmingham for example, drunk pedestrians and a high speed dual carriageway is always a great mix right?).

Fair enough, that is a reasonable point. There are definitely people who live off of busy roads. It would probably have to be taken on a case by case basis to determine if the better lighting is worth the trade off of circadian rhythm disruption. You are right that city centers do tend to be bright and noisy so the additional downward facing LEDs wouldn't add too much to the disruption but would increase safety.

+Emmett Wainwright Guess my data might be slightly out of date looked it up and apparently the share for rural roads has apparently been trending up significantly as part of the overall figure. Still urban roads make up for a non trivial portion so it seems unreasonable to ignore them, sure suburban housing is one thing so long as the "but some people do happen to live around there" argument isn't used to justify not having better street lighting in the city centre and such too. City centres in particular tend to have a dangerous mix of things like inner ring roads with relatively high speeds and a dangerously high level of pedestrian traffic for example. Sure there are mixed used developments along or near such roads though I would argue that if one chooses to opt to live in the city centre then probably not really in much of a position to complain that it's bright and noisy that kinda goes hand in hand with city centres in general anyway. Not being capable of taking steps to deal with the facts of life in a busy dense urban area like that is really kinda like moving in next to the airport only to complain that the planes make noise like err duh use brain before making choices next time.

First, I would like to say that you can get your point across without the sarcasm. However, I would still like to respond as you bring up a reasonable point, although not entirely correct. I am proposing bluer lighting on motorways and major or arterial roads. These roads, as of 2007, accounted for about 48% of accidents, about 48% of serious accidents and about 61% of fatal accidents according to RAC Foundation. If you could point me to data that says otherwise I would take a look. Another study I found by Michael Jackett and William Frith on Science Direct showed that increased luminescence did have a slightly higher impact on decreasing the crash ratio. However, I would like to mention I am not in favor of removing street lighting, but I am in favor of softer, although not necessarily dimmer, street lighting in residential or roads not meant for long distance travel. Drivers are generally more likely to fall asleep on long distance trips so roads that these drivers take should have lighting that emphasizes keeping them awake!

Technology Connections That's a good point about wildlife. I live in Minnesota and conservation is a big deal here, but wildlife isn't completely safe. Fireflies in particular are in danger. They historically aren't too shy of humans and their wetland habitats are protected (heck, they're known to live in roadside ditches in rural areas)... yet their populations have declined drastically. Researchers have determined light pollution to be the most likely cause of this because it interrupts their reproductive cycle.

+Emmett Wainwright So basically have the safest lighting for driving on the roads that have by far the least amount of accidents and make up an even smaller portion of fatal accidents (counting where any involved party dies not only the driver, highway accidents are more likely to kill the driver but the lack of pedestrians means that urban roads still take the prize for the largest amount of deaths because they have an even greater chance of the driver killing the person they hit instead) namely the highways and ignore the urban roads that have by far the larger number of accidents and by far the larger share of deaths. That makes perfect sense... but not so much.

Matthew Bartlett I agree with your stance here. I think using bluer lighting away from residences, beaches and wildlife areas and near Interestates, highways and other large roads would be a smart decision. While some people have brought up better directional control and the use of curtains, that doesn't necessarily solve the whole problem. Any time spent outside, or near windows that don't have curtains could still be disruptive. For example, there is a bright LED street lamp right in front of where I live. When we have a fire pit in our side yard or something the light shines to where we are. This isn't ideal as we have no control over the light.

Why not run HPS/2700K LEDs in neighborhoods and 5700K+ LEDs on highways?

+Joey Riso See that would be my thinking too generally exposure to street lighting occurs during the active part of your routine when you are out and about. If anything exposure to it during the active part of your daily routine for night workers seems more likely to alleviate the negative side effects of having your circadian rhythm out of alignment with your actual activity schedule. As for people complaining about lighting outside when at home, might I suggest looking into an ancient product called curtains they are still really quite useful in current year.

MrEdrftgyuji get blackout curtains. 10$ at a thrift store solves that problem and saves both energy and lives.

Good thing that with LEDs they would be able to adjust brightness and color temperature on the fly. Seems like a no-brainer to me.

What civilized country doesn't have a form of shutters on windows?

I absolutely agree with your point regarding people living by roadways using LED/blue light fixtures, but that can be fixed if people use heavy curtains and other methods of blocking outside light at night. I know I do, not because of blue light, but any light. But the upside of helping drivers stay awake and alert is great.

Perhaps placement of the lights- main thoroughfares would have more disruptive brighter (bluer) lighting, and the warmer and less intense lighting on secondary and residential roads. It wouldn't be too hard to accomplish that- while it wouldn't mitigate the problem entirely, it could go a long ways towards lessening the detrimental effect it had on people.

I have one of those in at my doorstep and I hate it

As part of my job responsibilities, I frequently get up at 1:15AM to drive to a wholesale market in LA. Driving at night I WANT my circadian rhythms disrupted. I WANT to be as awake as possible, not comfortable, relaxed, and ready to fall asleep - at the wheel! With respect to the aesthetic concerns the presenter mentioned, street/highway lighting is for safety, which should override aesthetics. There's a new medical building near me that has lighting with a yellow-ish glow, and I'm all for it -because aesthetics and security can coexist in that situation. But on streets and highways, in my mind, safety is the overriding concern.

Isn't that a design problem? If the fixture directs light downward and towards the street, it should not be an issue. Part of the argument regarding light pollution is that fixtures should direct light where it's needed, not scatter it indiscriminately.

Rainer Riegler They need to be very thick or blackout curtains to not be effected, trust me I have one right outside my room..

illiteratebeef I strongly disagree if there to be used in residential airiers due to the fact they can creat a bad sleeping environment that just sucks for said people and will led to lost GDP as well

yeah, but you also could use curtains

Not so great if you have a street light right next to your bedroom window.

You're exactly right, it's very possible that the melanopic light might be a good thing for drivers and safety. But for anyone living near a road (which is a _big_ number--even suburban neighborhoods often have street lighting) it can be very detrimental. It may also be disrupting the circadian rhythms of wildlife, which could have consequences we can't anticipate. Still, if better light _control_ were widely practiced, there would be less light shining into homes and the effect would largely be eliminated (for humans, anyway).

illiteratebeef Agreed, I would have appreciated a more in depth description of why the circadian rhythm disruption was a problem. I suspect he meant it would disrupt non-drivers or people living near the road which would be a problem.

This was very informing and good to grasp! Thanks!

Colour temperature of street lights is not something I am thinking when I am rolling down the street. In my case particularly, I am scanning the sides of the roads for deer which is a common problem in my part of the country so if the LED's provide more lights and less energy than it's Sodium counterpart, then I say, suck it up and deal with it. I'd much rather deal with a cool white glow than to spend $3,000 getting the deer shaped dent out of my hood.

Are we considering the circadian rhythm of the driver or surrounding houses? Because delaying the sleep onset of a tired driver on the street could actually be a positive. Of course those living close to those fixtures would be negatively affected

4000k and i'll be happy

Here in Dorset, England we have the street lights turn off entirely after 1am when most people are back home asleep. It is great for astronomy :D

Since the moon & stars give off a bluish light, do they also disrupt our circadian rhythm? I doubt it. The difference here is likely just the brightness level is much lower. Given that we can perceive our environment much better, even in dim 5700K light, it’s my guess that we’ll land on the LEDs but dimmer than most current solutions. This way you get a good balance of maximum efficiency while still being slightly safer than HPS.

Where I used to live they replaced the streetlights with LED based lights. During the summer I hated them because the heat meant I used to leave my blackout blind slightly open to let cold air in, but the new lights were poorly designed so you would get a relatively intense light in the bedroom compared to the ‘warm’ light of the old ones. For residential streets I think more care needs to be taken over the design/implementation.

It seems kinda pointless to worry about blue light interrupting people's circadian rhythm when these same people will blast their eyes with blue light from their phones and screens when they return home.

I think the best solution is to have the white LEDs on the main span of the highways but as it goes into the city or near suburban it should be changed to a softer LED but not completely yellowish. However, if the span of the road is higher in accident count or in mountainous areas, it should be in White LEDs to make the drivers to "wake the F- - up". whereas the street lighting around suburban and airport areas should be in HPS or similar lighting setup, with good protection from the skylight problem...

hi Alec i watch your channel for some time and i like it a lot but this video led me to two conclusions - video longer than 10..12 minutes becomes too long to have just a pop-science-coffee-break (i compare it to vsauce or numberphile or smartereveryday channels) this aligns such longer movies to the other... heavier category ;) - there is a lot of numbers which could be represented pretty well on graphs of some sort i mean these comparisons of the influence of wave length and stuff it doesn't mean this video was bad - no no no it's great but it forces me to split it or to move it to to-watch-later playlist unfortunately both will probably mean never-finish-watching-it :( it's not a complain just an observation of my habits which can be more common i suppose keep making pop science Alec best regards

Another option to save energy and reduce pollution is to *remove* street lighting. People do not appreciate how good it is tonhave dark neighborhoods until they spend time in one.

Save energy for what???

But what about .... SOLAR FREAKIN ROAD WAYS

I wonder what the effect of how a well lit area would effect safety of nearby less lit areas, where the lighting has suppressed night vision, if this is a significant factor I would preference the longer wavelength lights which don't effect night vision as much as bluer light.

LED lights suck.

I have changed my lights to 5000k and cooler in my house and around. I did it knowing it will keep me up during the winter where we only get 4 hours of sunlight some nights. Coming from the south originally I wanted to mimic the sun schedule I was used to. It works great and my productivity increased a lot. That and my house now looks like a laboratory from the outside.

It's funny I actually like the 5000k aesthetics more than the yellow light.. one aspect you can use for using the yellow warm lights is that it mimics fire or candles and can deter insects where as 5000k or cooler attracts insects

In at least some places, we could use L.E.Ds embedded in the roadway instead of retro-reflectors and streetlights. Signs beside the road would also have back-lights so they can be seen without headlights. Here, cars wouldn't need headlights as opposed to marker lights. It is similar to airport runways.

I find all LEDs to be inferior lighting. There is something fake about it. Why is the world embracing it like it is the holy grail? Can't people tell LEDs give off deficient light that plays tricks on the eye? California has regulated incandescent bulbs out of existence and I feel a part of me has died, but I will survive with the 100 incandescent bulbs I am hoarding. Hopefully they last long enough for me to show my future grandchildren that once upon a time REAL light from a burning filament made the night feel wholesome and magical.

Good Sir, please do mind the entropy. Best wishes

I'd be okay with bright white LEDs on major highways and surface roads (ie anything with a state or federal number) and yellow on everything else. I think that would be the best mix of uses. Oh, and the number one place I'm looking forward to LEDs being installed? In the Magic Kingdom parking lot, which has the ugliestiass light pollution of anywhere I've ever seen.

Has any studies been made for motion controlled street light features ? If motion control could be done cheaply and reliably (big if), it could solve a lot of these problems.

I like your choice of NOT putting music in your videos. It keeps the whole thing very focused.

You are the most unbiased and objective youtuber i have ever seen. Thanks for "Enlightening" us with your deep research.

The aesthetics are subjective. Once the blueish light is the norm, people will adjust and eventually prefer it. Perhaps. Maybe. Well, I like it.

That jacket fits you like a condom on a cactus.

I love blue light. :)

I have a major issue with topics relative with circadian rhythms, and it's that I'm not quite sure how does one measure it, for instance how long do you have to be exposed to blueish light in order to alter your rhythm or from what distance? How big is the impact from LED's vs. mobiles and computers or with the lights indoors? (also even with the correct light, most of the people can grasp 7 hours of sleep) It's an unavoidable harm in this time?, Does this alteration also happens in other beings?, such as trees, recently in parks near my place greenish light sources have been installed in order to prevent "stress" on the plants, nonetheless all of the videos on this channel make everything fascinating and make me realize that there's a whole world in the most common things! thank you so much for the effort and also for giving me anxiety and make me curious about the things around me

Would love to see a video on high end, medium pressure mercury lamps such as those made by Heraeus, LSI, or ETA+.

I don't understand why most HPS street lamps have defractors protruding from the fixture if they cause more light pollution. Why don't they simply not have them so they are full-cutoff and don't let light out upwards?

night lighting is the work of the devil. if God wanted us to see things at night, He would have given us the technology to do so. don't believe this propaganda. I know about these things, and can be safely trusted.

I personally like the 'daylight' color of the led street lights. I have same 5700k led lights in my house.

Stick with what works in the past, just update the tech.

Here's hoping self driving cars make all this moot and we can all experience real night again

At 10:04, the "well lighted" road shown is actually how all street lamps here in Tucson, Arizona work. We actually have a city ordinance (that's been in effect for at least 25 years) that mandates that all street lights maintained by the city to not shine light upward. This is because the light pollution would adversely affect our local astronomical observatories (Mt. Lemmon, Kitt Peak, and University of Arizona).

Maybe (although, this is a macro idea that would require quite the societal shift in thinking) we could all stay home at night. LOL.'ll never work.

Your hair looking better every day, I don't know what are you doing but keep it up.

I actually understood all this tech stuff. I wish I had a teacher like you when I was at school.

IL56 in Oak Brook!

I don't know if it's because I am partially colorblind, but I like cool light way better than warm. Good to know that it might be messing up with my sleeping cycle, though (I use cool temperature lighting in my main room)!

Can't we mimic LEDs and put a blue filter over the sodium lamp?

With all these pros and cons, if it were up to me I'd say, just stay the course and keep HPS lighting. To use a famous quote with no definite attribution, "If it ain't broke, don't fix it."

You make me feel smart haha. Love the videos and appreciate the time you put into them!

Cool video. On aggravating thing I have found driving at night in areas with poorly designed streetlights (regardless of source) is that the brightness of a poorly aimed light ahead is much brighter than what it is illuminating... They really should have a well designed lens or snoot.

LOL Kommunist Kree Kompany needs to put it back in their pants and quit playing with it so much, because the claim of 95% lumen maintenance at 100,000 hours is BULL SHIT! I see Kree "EDGE HO" units, mostly the 5000 K units, visibly dimming and turning a pale pastel green color from phosphor degradation in the first year of use, and it is prevalent in parking lot lights in our area. To make a far out claim like that when these things haven't been on the market that long, is far fetched at best! If the drivers don't die as electrolytic capacitors fail (they will!), then the LED's will color shift greener in color as they dim out. They are lying through their teeth with this claim. Video was excellent, but you came across as pushing the TRASH Kree makes. I light my yard with mercury vapor, better than either HPS or LED. Cheers!

Holy shit this video seemed to cover everything.

I absolutely love that yellow orange sodium light.. its so much nicer than the obnoxiously bright white LED lamps..if they could recreate that color with LED lamps I wouldn't mind. I do have to admit that it's more of an emotional link for me... My brain seems to have linked that sodium light with some of my best memories.

+Technology Connections - Your sunlight comparison misses a key point: Your eyes can withstand blue light from sunlight (including the rest of the spectrum too) because your irises are triggered to constrict upon walking out into daylight by the ambient sunlight reflecting off everything in view, which then significantly protects your eyes from even brief direct exposure to the sun. Now contrast that with night time driving while your irises are likely very dilated by comparison to daytime. Now consider when your eyes are assaulted by the random harsh blue glare from the occasional LED street light. LED street lighting is more directionally focused and blasts more additional white/blue light out of a few little emitters no bigger than your finger print than existing street lighting today is even capable of. That's extremely concentrated light output for your retinas to endure, ESPECIALLY through dilated irises at night. The effect is similar to enduring a xenon camera flash, and is quite contrary to any idea I'd have of "safety". The temporary lack of recovery of your retina under such conditions is considered temporary blindness and would obviously be quite dangerous while driving.

Groton is pronounced GRAH-tun (rhymes with cotton), but it seems everyone not from around here calls it GROW-tun. Anyway, interesting topic as always.

Safety and energy-use reduction override personal color preference and claimed circadian rhythm issues. (IMO)

I hate it when blue light disrupts me napping during long night drives.

A very informative video. Thank you. Unfortunately, this video doesn't address the only thing that really matters to the VAST majority of individuals, the cost to retrofit, or replace, and operate. I don't care what color the lights are if the expenses are higher. On that note; I have been driving for 25 years without an accident, so...........if the operating cost is the same, or less, and you pay for the retrofit/replacement, then I'm on board. Replace HPS fixtures piecemeal as they fail? No. I do not want a patchwork of different colored streetlights.

Weird. I prefer the yellow lights. The bluer lights are outright dangerous on fresh blacktop when it is wet. The road is completely invisible. It's like driving in outer space. That's why I have both the 'pure white' bulbs for my headlamps, standard bulbs for my driving lights and a yellow for fog lights. I also dislike when the street lights that are the same color as headlamps. There are many corners near me where when coming up on them; the color of the streetlamp makes me always think a car is pulling up to that intersection.

Kudos! Very interesting topic!

I'm OK with not being lulled to sleep during drive time.

You need to do a report on how RESISTIVE (filament) loads and LED's (non-linear) Non-resistive loads appear to the operators of AC power grids. Not at all easy to deal with. Those NEW LED fixtures add a lot of problems to the nation's power grids operators. Solution? It will take massive investigation and research in the field and lab to come up with a solution.Meanwhile,the tail is wagging the dog.

I like your shows. What I'm referring to implicitly is the loss to the power grid of millions of RESISTIVE Illumination devices( incandescent bulbs) and SMPS devices that have become millions of phantom loads Predictive Data,lost (not available)

The load from any discharge lamp is nothing like resistive, in fact it's quite inductive. Without a capacitor across the ballast to correct the power factor, it can be as bad as .35. The LED fixtures I used as a reference has a power factor > .9, which is on par with or better than the PF of a non-capacitor HPS ballast combo. Nothing's getting worse with LED, in fact it's almost certainly improving.

I remember walking through Tokyo and noticed the moon was just a dim disc. Jupiter and Venus were faint specs in the night sky.

I find LED lighting to produce a shadowy look to everything. Even super mega bright stuff like those high power flashlights tend to give everything a shadowed look.

There's another aspect of LED that should be addressed: failure mode. My city is changing to LED streetlights and every few weeks I see one flashing rapidly at maybe five times a second. It's extremely distracting and relies on the city changing the light quickly. Sometimes that doesn't happen. Is it possible to design a driver that fails to 'off', instead of 'fail to flashing'?

One thing I’m not getting, if our eyes are more attuned to bluer light in nighttime conditions, presumably as he said, because moonlight is bluer, and bluer light is supposed to disrupt circadian rhythms, then how is it that the moon doesn’t wreck circadian rhythms?

I don't really like LEDs at home. I use halogen as their output is more pleasing and, with dimmers, at night I can make them glow much warmer not interrupting sleep rythm. But for street lighting LEDs should be the only choice. Especially when you consider cost, and how many cities in my country actually delay turning the lights on untill it's almost completely dark to save money. Also, I'd say lights that disrupt your sleep are actually better for highways so people don't fall asleep at the wheel.

LED street lighting is bringing that '70s and earlier look back. I like it.

Very good research! I don't think that "blue" light damages our eyes, but that over hundreds of generations, through evolution, our eyes are more "attuned" to the red/orange/yellow light of lanterns, candles, firelight, etc. which we were using for millennia.

A interesting solution would be to use different types of fixtures for different areas. I am thinking about using HPS lighting around more residential areas, and then use more cool LEDs on freeways and other areas where you need the higher visibility.

Keep it up ya geek.

Really we should use green lights, that's where the peak of the night time sensitivity is, and the reason why NVGs use green.

Do you have a cold ? :(

I feel we should strive to limit the impact of things like lighting. Should nightlife be facilitated to the extent that you can't get away from it? It seems with these things that need follows availability, which is odd. This is all while basic biological needs are neglected. Acting on that kind of whim isn't very wise. As Kris M described in this comment, even supposed benefits aren't absolute, and turn out to be countered by issues popping up elsewhere: If we must have light (noting that less light also uses less energy), it should be yellow and as dim as possible. Edit: YouTube breaks the comment link somehow. Copy and paste it as text to find the comment.

What's wrong with circadian rhythm at roads? Somebody wants to sleep at highway?

just ordered HIDs for my 99 BMW, then realized I'd be one of those douche bags who runs HIDs in a reflector housing. returned them asap and kept the halogens.not related at all, but it's at least lighting related

This is my favorite video you've done so far. You talked about this issue from a number of different angles and societal impacts and safety. Very Well Done!

Such an awesome presentation. I think one mark of a skilled teacher or presenter is the ability to captivate their audience regardless of the topic at hand. I wouldn't consider myself a huge fan of municipal lighting challenges and technologies, nevertheless I found the entire video fascinating. I look forward to watching your channel grow and can't wait for the next installment!

considering that most TVs and cell phones are LED now anyway, should they really worry if our outside lighting is the same?

This past winter my municipality replaced the lights in my neighborhood with flat-cobra head LED fixtures. Different, but brighter, IMHO, to the point I believe you could play catch under a row of them. Almost reminds me of stadium lighting in the light color, though not nearly as bright.

Wow, this is a pretty thorough video! I would have been curious to know about bug attraction of LEDs. Interesting content.

some of the street lights where I live that are LED will turn off if theres no activity near them for a long time. First time I ran into one I was puzzled wondering if the light just came on :P

This was such a cool video! Thanks for the deep dive, I found it really interesting.

Damn, you probably aced your oral presentations in school.

they went from halide to sodium few years ago overe here and i noticed that much more light leaked into my room since the lamp is right infront of my window, especially the color annoyed me to a point where i cant sleep (window blinds that have slits). now they changed it to LED and no light at all leaks into my room but the roads are well lit. much better. but they have awful flicker. not visible directly, but in peripheral vision and while moving it becomes annoying. the led lamps are focussed to the road better, the sodium and halide emitted light everywhere. also the multiple leds cause weird bokeh in photography, you can see every emitter instead of a round spot

i really like your videos on lighting.

3700-4200k as a compromise?

One of my favorite video of yours so far, especially the addendum at the end about blue light being harmful and the "science" about it. Thanks for great content!

This channel is awesome

the advantage with LEDs is that they can adjust the HUE of the lightning combining different LED colors in one lamp. I have a lantern with "day-like color" and the light is really pleasant

Only in R-G-B (red, green, blue) LED arrays, but they are hopelessly inefficient, and 65 lumens per watt for a typical white LED fixture is dismal as well.

Another great video, love it

I really enjoyed this! I genuinely love your work.

Wouldn't disrupting sleep be a good thing for night driving? It'd help prevent people falling asleep at the wheel.

fantastic video, as always.

I think you've made one major flaw in this video: Assuming that we see using scotopic vision in street lighting conditions. This is *not* the case, as far as I can tell. Scotopic vision only starts to kick-in down at 0.001 lux - and even mesopic vision only really starts when you get below 1 lux - while street lighting is at a minimum of 3 - 5 lux (sometimes as high as 15 - 20 lux). This is pretty squarely in the realm of photopic vision. IMO having street lighting in the photopic range is actually pretty important, as our rod cells can be easily over-saturated by bright light sources and take a long time to regain sensitivity. I imagine it'd be quite dangerous to have to rely on our scotopic vision on the road; especially with the risk of getting flashed by oncoming headlights.

I live in Bournemouth UK and they are in the latter part of a plan to change every Sodium lamp in the town to LED. The streets feel much safer and there is less sky glow in the town these days.

I like how the cool light looks on the road. I dont care for it in a house though.

Please record your videos in 60 fps it would look much more smooth. Do it if you can

The first time I saw the Milky Way (outside of pictures in a book or at a planetarium) was in the desert in Saudi Arabia prior to Operation Desert Storm. I'm from New York City so I had never had a decent view of the night sky.

Cherry Springs State Park in Pennsylvania is one of the very few dark sky areas accessible to the public on the east coast of the US. To preserve this both the surrounding campgrounds and nearby roads use special street lights that minimize light spill.

seems like there's probably enough light to keep your vision somewhere in between. and light pollution sucks. I remember when it was pitch black where I am at night, then they expanded the highway and added a bunch of lights and the whole horizon in that direction is lit up at night now :

I like his jacket.

I think I am probably way in the minority in that I strongly prefer white or even slightly blue lighting in most circumstances, including indoors. In my bedroom I only use 200W equivalent "daylight" CFLs and they have improved my mood quite a lot (I think this is partially due to my suffering from winter depression, so the "daylight" imitation has benefits for my mood). But I do really enjoy the more accurate color-rendering of white light, as well. But there are a few situations in which I prefer the more yellow light, such as for the string lights that I keep in my backyard for summer gatherings. The ample amounts of sunlight during the day in summertime make me less susceptible to poor mood, and I actually start to prefer the yellow light (but only for my back yard). My community (suburbs of Washington DC) is among those that have begun to replace high pressure sodium street lamps with LEDs, and I really enjoy the accurate color rendering of the grass and surrounding foliage. It may be worth pointing out that I don't drive as I don't have a license to do so, so it's largely an aesthetic preference, but as a pedestrian I do appreciate the increased visibility as well. The fact that I absolutely refuse to use Flux on my desktop PC probably also contributes to my being somewhat of a night owl, since I find those orange shades kind of ugly. However, as an avid astrophotographer, I do very much recognize the limitations that I face when trying to take these photographs in my community, and the LEDs arguably only exacerbate this problem.

holy shit that was a lot to take in ... no wonder i get blinded by the new led lights in cars the light-wave is tuned to be more sensitive to our eyes especially if theirs no street lighting

So the real answer here, is get those self driving cars working so we don't need the street lights at all.

Why not use different types of light in different areas? Use the white LEDs on the busier freeways, and use the warmer LED or HPS in residential areas. Also would like to see sensors which shut off some of the lights when the road is empty.

Alessio Sangalli, while I do agree with your reasoning regarding lighting on highways, I believe it is much safer in those not so uncommon times when unscheduled stops do occur on the side of the roadway. Roadway lighting is typically avoided on highways unless required for obvious or practical reasons. The most likely cause of death for on duty police officers is being struck while on the side of the road. Lighting is not terrible when used responsibly. The place where pedestrians are frequently out and about at night is their residential neighborhood. The lighting should be as safe as it can be in these areas. Maybe tighter controlled street lighting is a better answer than appealing to those people that may have issues with their circadian rhythm. As pointed out in other posts, there are ways that people can mitigate the effects by changing things from within their homes or taking supplemental melatonin. There are likely more detrimental lighting products located directly inside homes anyway. It's a complicated issue with few simple solutions at this time. With so many impractical challenges, is street lighting even worth doing at all?

if it bothers you at night just pull down your blinds or close your shutters

What if public lighting were set to a trigger mechanism? In some supermarkets when you go down the frozen food section, the sensors turn the lights in the freezers on and off based on proximity. So if we included similar sensors to the outdoor lights so that the lights turn on when a car or person is nearby.

Keep the LED's to commercial, industrial, and main thoroughfares (Highways, divided avenues, ETC.) Keep the sodium, or a much lower temperature LED in residential areas. Sure you have to keep 2 main types in supply, but local government covers the residential areas for lighting and the regional covers the highways, each group only needs carry one, and maybe a few of the other to help out.

I was about to say the same thing. While this may be bad for people living near these streetlights, it could be the difference between a driver getting tired or not.


Your Ken M. impression is bad and you should feel bad.

Steamrick I disagree, lighting on highways should be avoided altogether. There are not supposed to be pedestrians along the highway especially at night.

If nothing else, I'd want lights with high melanopic ratio used on highways, where there's few people living near but a high risk factor of people falling asleep on long, monotonous night drives.In residential neighbourhoods, a less disruptive light colour might be a good choice.

I wonder if the effect on wildlife could be mitigated by closely matching the color temperature of moonlight. That would make 4500K a good candidate.

mhh why are the more bluish xeonon lamps in cars disappears ?    if we can see blue better ?

So... LEDs for Motorways and High Pressure Sodium for the streets then :)

Excellent video! I feel like my city designers should watch this - light pollution has gone immensely over the last 3 years here, very much since the introduction of LED streetlights. What has once been a great view of the Orion Nebula is now just some dim glow... :(

how about indoor lighting and use of led's on automobile head lamps?

Only thing I don't like with led lights around low speed streets is now its more difficult to determine if that light I am seeing is a car or just the streetlight (as the LED lights are at times brighter then car headlights and if the car uses led or high powered headlights sometimes matches the led lights on streetlights)

Who in the world would prefer the sickly orange glow of a sodium lamp!? Freakin LED it up!

Our council is phasing in LED lighting when the old sodium lamps fail. The LED lights tend to splatter light backwards towards the houses making the upstairs appear to be in daylight. This is very annoying for those that have the lighting close to their bedroom windows. I've also noticed that the light from the LED lamps gets scattered much more by fog than the light from sodium lamps. With the lenses added to LED lights, this creates a wall of blue/white light that makes driving much more difficult at night whereas with the sodium light there is no wall.

What would your recommendations be on a color that would be more visible during night time to place on your car. If your citations are correct placing a more blue light on the headlights of your car will increase your sight's range. but will it also allow other motorists to notice you easier?

Enjoyed this video so much.. I too rather prefer the warmer lighting. Even my outdoor lighting around my house I use warmer LEDs. I think mine are actually 4000k temp.. So not as warm as the street lights, but not harsh on my eyes either.. Also I noticed some LEDs, particularly really bright ones in like used in airports/terminals hurt my head and make me nauseous. Also I purchased some RGB strips from china and thought the blue would look great, but when I find is that after an hour the blue gives me a headache, yet if I use Red or mix them to white its not an issue at all.

This is why emergency vehicle lights are red and blue. Red sensitivity for daylight, and blue for night. Hell, I feel you could do a whole video on that.

Disney used Sodium Vapor lights for a compositing process in film production, back in the 1960s:

I wonder if light penetration through precipitation/fog is significantly different as the color temperature changes. I’ve always heard that colder light is worse through precipitation, but it may be too subtle to be relevant to street lights.

I find the aesthetic argument highly subjective. I for one prefer cooler color temperature light. Additionally the greater CRI of most high color temperature lights is an additional safety feature. Color recognition helps in spotting obstacles. Also for people like myself with mild abnormal color vision, it helps greatly.

I still prefer the orange glow. It is just something I find ubiquitous about night time, also I always found bluer light irritating (why my displays tend to lean to the warm side). That being said, wouldn't affecting circadian rhythm be good in many cases? If it does that means it is less likely to fall asleep at the wheel (the most likely thing to cause a crash).

The amber glow of sodium lighting also doesn't kill night vision as much. When you look into darker areas away from the light, your eyes adjust quicker than when dealing with bluish colors. Also why those cars with extra-blue seeming headlights are annoying in oncoming traffic, they more effectively blind you.

My experience has been that you *do not want* blue-white lights at night. Not for headlights and not for streetlights. If you should happen to glance directly at a light source, you will be temporally blinded. The yellow-orange of HPS looks like crap, and it does seem to be dimmer than other sources. However a well designed and properly sized HPS fixture will illuminate the same area. But that does not mean we should stick with HPS. LEDs are the future. But 5000K and higher LEDs are wrong for night vision because of the accidental blinding effect. 3000K to 3500K is a much better choice. BTW we live in a neighborhood with no street lights. We put up our own about 2 feet back from the edge of the street (and mounted our mail box to the pole). Back in '86 we started with 150W mercury vapor. Replaced it with equally effective 70W HPS. And about 2 years ago replace that with 35W 3300K LED. (Effectiveness measured by the size of the light circle on the street.) The mercury vapor threw light everywhere, not just downward, and would kill anyone's night vision. The LED light looks great and like HPS is not dazzling to the eye.

Man, that scene at 1:54 is really weird. I actually can name exactly where that is. The Wannamakers sign and the Car dealer I pass everyday on I-88. Super weird to see that in a video on YouTube

This is my favorite video you've made so far. I love it when you really get into the minutiae

Very illuminating video.

I haven't seen any LEDs used in street lighting yet here in NJ (where our motto must be "if it ain't broken, don't fix it," considering the surprising amount of _incandescent_ street lighting we still have in use), but I am starting to see it used by car dealers, quite a few of whom are now using *extremely* bright LEDs to light up their lots. It's great for giving nighttime shoppers a better look at the vehicles, and also detering theft and vandalism, but it's distractingly bright when it's near a roadway and has all the other downsides you mention.

So bluer light keeps drivers more awake and thus more alert at night while also needing less power and less light saturation to achieve the same level of brightness, and the downside is...? Slight disruption to individuals circadian rhythm? they're already out driving around at night, seems like a fair trade off.

and the LED blue light problem is why I use a blue light filter coating on my glasses. I recommend anyone that wears glasses to look into it. Its AMAZING.

In my opinion disrupting your circadian rhythm is actually another safety benefit, as if you are driving at night anyway, you need to be awake. Circadian rhythm disruption is a major problem of modern society for many reasons, but kind of a separate issue...

1) Personally, it's not so much that I miss the color of the HPS lamps as I miss the variation in urban lighting between the HPS and Mercury vapor lamps. 2) What's your take on Sulphur lamps? I'm not aware of them being used for street lighting, but they're an interesting technology. See:

Every time I make the trip from my home in Michigan to Chicago, I always notice the LED lighting on the highway near Chicago and it looks amazing to me.

My region just installed citywide mixed-type LED street lighting of various colour temperatures. *All of it* makes use of really bad lens designs that turn the LED into one ultrabright point source and create this annoying, potentially distracting side-glare effect that gets in your eyes at night (especially when driving). You'd think someone would have figured this out before it got to market. Even the old sodium lamps had better dispersion, they'd put the light where you actually needed it. I imagine it's just a matter of time before retrofits happen (how many car accidents do they need to see first?) and in the meantime, they've been allowing the request for installation of aluminum strips to deal with the side glare issue, on a call by call basis. Better than nothing, but good design would have been the best solution from day one.

Where I live we have LED street lights and I like them a lot more over the older sodium light. They are so much better.

Thank you so much for doing this deep dive as a child of the 60s who grew up with mercury vapor lighting at night I was so discouraged when sodium ruined night illumination. Thank goodness, ahem ENGINEERING for LED's. White, 5000k hot and gleaming. Long Live SI!

Street lighting is something I never really gave two thoughts about, but these videos have been super interesting and informative

I am a huge proponent of LED lighting, and definitely agree that it is the right way to go in street lighting. One complaint I have about it, though, is in situations where "full-cutoff" LED fixtures are used as a replacement for old HPS fixtures that had hemispherical lenses with no compensation made for the differences in the light distribution patterns. For example, there's a small town near me that replaced every HPS lamp along a major street with LED. They did this by removing the old HPS head and just sticking a new LED head on in its place, nothing more. The problem is, the lamp brackets were originally mounted too low on the poles. This wasn't a problem with the HPS lamps since they also emitted light out the sides at an angle, but since the LED fixtures are full-cutoff fixtures, this means that instead of the entire street being lit relatively evenly, there are now small, sharp-edged "hot spots" of light with gaps of total darkness in between. To properly replace a non-cutoff HPS fixture, LED lamps really should be mounted higher. BTW, one potential benefit of LED tech not mentioned is since they run on DC at a much lower voltage than HPS, as the tech continues to improve it should eventually become possible and economically viable (if it hasn't already) to integrate battery systems that allow street lights to continue working during power failures, or even entirely off-grid using solar charging. Speaking from experience, I know it would be nice to have a little bit of working street lighting during blackouts, even if it is at reduced brightness (lower output on all fixtures, or only key/specific fixtures being battery equipped).

I far prefer cooler lighting, opting for all my LED bulbs to be 4100, 5000, or 6500k in temp. And I feel that circadian rhythm disruption is far, far overplayed in the media. I sleep just fine after reading for hours with cool white LEDs. // I, too, am =not= a fan of light pollution. // What I'm seeing in industrial areas is overlighting with new LED systems, likely caused by installers either 1) not understanding that LEDs are much more efficient than their predecessors or 2) that they make a lot more money on larger LED packages. LED parking lot lighting is absolutely wonderful, and much more safe because bad guys can't hide as well under them as they did with LPS, HPS, or MH. // Thank you for a well-thought-out presentation. You covered all the bases, something I don't often see. Kudos, TC. I saved your video.


As someone who drives late at night every days, I wish streetlights would disturbing my circadian cycle way more to prevent me from sleeping while driving.

I shrieked with laughter at “...can withstand the intensity of SUNLIGHT...”. You are probably on to something there. Thanks.

I thought I liked 6500K lighting then over time I found that it was actually hard to see with LEDs of that color temp. I find it much easier to see at 3000K not sure why but at 6500 things look harshly edged and difficult to make out objects and I can only see hard edges. With 3000 I can see the objects and be able to read signs. I am completely in the dark about why, pun intended.

For me, yellow glasses are great for driving at night. In LED and mercury vapor lighting they cut the harsh blue but don't really seem to decrease what I can see. They are really great in cloudy/rainy conditions too.

I have an odd nostalgia for the sodium lamps though. The orange color reflected off the clouds particularly during the winter, and it was strangely beautiful.

The "circadian cycle disruption" is actually needed! You _must_ be alert when driving in highways. That's what the rise of melatonin causes. We already see lots of bluish lights during the night, it doesn't irrevocably compromise our circadian rhythms, the effect is short-lived and we need the alertness. HPS lights due to the non-circadian interference allow the driver to become sleepy, drowsy and much more prone to accidents.

Amber colored light is easier on your eyes at night and the amber colored light fades off over a far distance, while blue light can be blinding and vision cuts off at a faster rate as you approach the edge of the light, because your eyes are overwhelmed with the blue light. I suppose if you could have ENOUGH blue light to avoid having the harsh edges BETWEEN lights, then it would matter less. Also, the higher the color rendering index, the more details your brain will be forced to process when you drive, so I am thinking that long distance truck drivers, probably prefer to conserve their brain activity for staying focused on driving, not spending time subconsciously comprehending the exact color of vehicles and the color of the leaves on trees and so on. As far as which lights I prefer? In my home, I have both orange and blue colored lights, and i use whichever I want at the time and use both at once if I need maximum vision (like for cleaning). I am going to make a wild guess and say High Pressure Sodium lights will PROBABLY be around for AT LEAST another 50 years. I thought LEDs put HPS to shame, and found out they still don't at all.

im going to comment before finishing the video.... the fact is that in my neighborhood they switched to led at the intersections and they suck....they light up just a little area and so brightly that the light drowns out the head lights from cars approaching the intersection we have lots of blind intersections... also.. the sodiam lights are better in the winter with snow... im so angry at the city for switching........

Doesn't the 'blue light spectrum' of the sun...go away at night... Thereby setting our circadian rhythm in the first place? Artificial blue lights are turned ON at night...thereby disrupting it? That seems an odd point for which to base your skepticism of blue lighting skeptics. Or am I missing some crucial logic? -The Internet Police

It seems reasonable to put 5700K lights on freeways, where you need long distance visibility, and (until the cars are really driving themselves) you really want people to stay awake, but put 3000K lights in residential neighborhoods to keep from disrupting everyone's sleep, and keep from getting complaints about the horrendously ugly blue light. Seems a good solution to me.

Great video. Disrupting circadian rhythms might actually be a really good idea for freeway lighting. I can understand that one would want warmer lighting around a residential neighborhood where people sleep, but freeway travelers would do better awake. :)

So much we'll research ed data.. thumbs up

omg... I saw the government report and actually smiled a little. I need to quit my government job.

Moonlight is **not** blueish, that's a matter of perception. Moonlight is actually yellower than daylight (color temp of 4100 K vs 5000 k, for moonlight vs daylight).

LED lighting has made driving less safe here. because they are brighter, they have been readily adopted and installed by most cities eager to save money. because of the increased brightness, they've been installed at large intervals, and because of this wide spacing there is usually no shielding at all installed, so the bright LED light is spread very wide. this has given us many bright light sources shining right into the eyes of drivers, causing pupils to narrow, causing reduced low-light vision - the same reason it's hard to find your way back to your dark bedroom after turning on a light in another room. this has led to an increase in night-time incidents, with a particular increase around twilight hours, yet the safety of LED lighting is still touted without mentioning the safety reduction caused by wide spacing and reduced shielding, and here many experts are also recommending drivers to keep their headlights angled as high as possible so they can see better, again failing to recognise that means everybody else also has their lights up, which makes people and other cars off to the side or after turning down a darker street harder to see.

The new LED lights do my bloody head in there horrible. My street had them put in and there really horrid to look at and makes everything darker. Wish they kept to Sodium lights there way nicer

I much prefer the cooler color and actually quite detest warm lighting in general

So wait, then is this also why the dinky blue LED on my computer seems to light up the entire room while the glow from the red readout on my clock radio hardly reaches the edge of the dresser it's sitting on? Because my brain is just wired to see the blue light more at night?

This video was very enlightening. You really shined on some misconceptions

1:28 The mitochondria is the power house of the cell

That's crazy because HPS lighting has always helped me see better at night, in the backyard or on the road.

I agree that I like the warmer lights in my house, but I don't care if they use blueish light on the roads.

I wish urban planners were watching this instead of an audience of youtube users...

All our street lighting is LED and have dimmed over time. I find it more taxing to drive with LED lighting rather than the monochromatic high pressure sodium lights. I really thought the higher colour temperature would be better but personally I don't think it is.

The only thing I didn't hear mentioned in your talk is that many replacement lights use multiple pin source LEDs without diffusers. This causes multiple confusing shadow patterns on the ground which are just weird, but they also mean that the light source appears MUCH brighter when you look up at the light. LEDs without good optics are just awful!

Light pollution along coastal areas where sea turtles lay their nests are a very big problem. Thanks for mentioning this. LEDs do offer a potential solution to this problem, but only if communities choose to use them. Turtle friendly LED lighting should be required in all beach communities where there are turtles nesting. If you live in one of these communities, please contact your local officials.

I’m an electrician and just watching your videos has made me sound way smarter that I am when having meetings with lighting designers

The pedant in me is pained by the talk of using energy rather than using power. But that’s how nearly everyone talks, so it’s no use. Otherwise a good video.

No they shouldnt, Leds have glare ,and there is more contrast, or percieved brightness varience, unlike daytime when everything is bright ,long drives become an evening of looking into a slow strobe, because a part of our body is more sensitive it don't necessarily mean its a good idea to kick it. Our eyes have an iris for the whole day and night thing. Stick to fuzzy orange light. I would not call driving with tired eyes and the onset of a migraine safe. This put leds everywhere thing seems to be an office wombat fad.

My understanding is that bluer light scatters more in fog also, hence people like yellow/amber fog lights. IDK if that affects street likes the same. Plus, redder light does not have as much of an impact on night adaptation, so if you are driving down an unlit highway and pass a section of lit intersection, bluer light would make it take longer for your eyes to readjust to the dark. That is just what I have heard, I don't know if it's true but it makes sense.

Honestly, I've seen a lot about blue light disrupting sleep but I've never experienced anything like it. One thing that makes me NOT sleep at all is seeing that orange glow coming through a window. I have blackout curtains on all windows just to keep it out. At the same time, my alarm clock has a large, bright LED face with blue numbers that can light the room up blue. I can sleep with that. I can't get to sleep if street lights are shining in though. No matter where I am. I've always seen people use f.lux on their computers or phones to eliminate blue light so they wouldn't disrupt their sleep, but I tried it and it had no real effect on me, but the colors being wrong annoyed me more than anything. Could be just that I naturally prefer bluish lighting over "warm" colors. I replaced all the warm colored CFLs in my apartment with 5000k LEDs.

Great video! I find this relates closely to my life, as I do a lot of LED retrofits in fixtures that were designed for metal halide lighting. The LED industry has come a long way- with one $85 LED module I can replace a $30 metal halide lamp. Doesn't sound like a deal until you take into account that I'd typically replace that metal halide lamp 2 or maybe 3 times per year plus a possible ballast at $65 or 2-3 capacitors at $20 each. With the LED fixture... well I haven't had to replace one yet and I've been installing them for 4 years. I can just eliminate the ballast and capacitor entirely from the circuit which reduces the number of modes of failure. Plus they run at 30W as opposed to 400W. I install LED modules in lighted channel signs which formerly housed neon tubes and a 1000W power supply. The 6 neon tubes in each sign are $125 apiece. I can replace the whole kit and kaboodle for $18 worth of .75W LED modules and use a 60W power supply and the result is brighter than the old style. I really love the look of bare neon, but in these channel signs the neon is hidden behind translucent lexan anyway, so you're certainly not losing any great aesthetic quality.

My main concern with street lighting is it screwing with my circadian rhythms, and dark adaptation. I'm a cyclist, I ride mainly late night and early morning. It's a major pain to turn off a well lit street onto a dark road or trail and be blind for several minutes while my eyes adjust. It's not as bad as being blinded with high intensity automotive headlamps, but still no fun (turn off your goddamn highbeams people!)

HPS lights....look at your vehicle closely when you park under one at it's hard to guess the real color. It all looks gray at night under HPS.

Also - amazing production quality !! Love these videos; Just one complaint — try not to repeat yourself this much, you say some things 4 times in almost the exactly same way

Isn’t the bluer light keeping a driver awake a good thing?

I too HATE the blue lights ..

Make night time dark again. :D

LED's are also being used more indoors now and i really despise that cool colored lighting in my own home, efficiency be damned. it makes everything feel so uninviting and sterile.

LEDs also exhibit fading as they age, although they do last a lot longer than MV bulbs. Still, it's a problem when the city's street lighting company adopts a stance of considering a light "in good order" if it still emits _some_ light.

Great video as always, this also brings attention to how GODDAMN ANNOYING blue LED indicators are at night. They look "ooh soo pretty" at daylight/well lit situations, then at night... bright. VERY bright. Routers, cable TV decoders, the damn decoder's LOGO, all full of LEDs, some of them... blue. The Nintendo 2DS also is quite annoying in this sense at night, the screen can dim enough, but the power indicator makes you wanna play at low battery only (that is... until it blinks on your face TWO red LEDs).

I would think using cooler light for express ways, and warmer light for inner cities/towns would be the way to go. I've experienced dozing off at the wheel on long trips. Not to the point of causing an accident, but it very well could have. But then, whose to say how alert you can stay with different lighting. It's just a thought. And, for sky glow, I moved from a village with none, to a city with a lot, and back to the same village. The difference is significant. Even a few files away from the city, the glow just overpowers the night sky.

Don't you mean lower temperature when referring to white light?

Another potential benefit that probably won't happen (due to instrumentation costs) is because LED lights are (nearly) instant on (especially compared to HPS lights...). Only turn the lights on when traffic demands. If there are no cars on the highway, turn the lights off. If that large moving object (car, truck, etc) on the freeway has passed the lamp position, turn the light off. I don't know how far ahead of the vehicles the lights should turn on, but I'm sure road safety engineers would be able to figure this out. The sensitivity of the size of the moving object can be adjusted to different sized objects for illuminated areas that have different types of traffic (down to people sized for parking lots and sidewalks). Then only the amount of power to run the sensors and decision making electronics will be needed if there is no one is there to need the light.

Me when you start talking about scotopic and melanopic lights:

I don't like LED street lights... Sure they illuminate the roads, but the shadows they cast on the sidewalks are too dark. Makes it impossible to see anything unless you're directly underneath the lamp.

A huge issue with LED lighting is the real world life expectancy and maintenance cost. Sodium lamps with magnetic ballasts are extremely long lived and well proven. There are very few points of failure. In contrast LED street lamps haven't been out for as long a typical sodium street lamp lasts and they have MANY more points of failure. If they are a high voltage design they use a large number of series LEDs and a single LED failing can cause the entire fixture to fail. And if they use a switching low voltage power supply there are many points of failure in the power supply such as electrolytic capacitors that may only last a few thousand hours or less. Street lights operate in relatively harsh conditions not friendly to modern electronics. A lot of LED fixtures are made by relatively new, and often Chinese, companies. Many have already come and gone which makes quality and warranties dubious. The cost to repair a street light is high requiring a boom truck, specialized expensive labor, potential street/lane closure, traffic personnel, etc. Imagine Small Town USA putting out bids for replacing all their streetlights. The low bid Chinese fixtures/lamps win but it's still really expensive. After 2 years they start failing right and left and the company is out of business. So much for cost savings.

My area in England has changed to LED and must say it makes driving safer! I also work for a company that put up the new LED lamps and they are fully adjustable to the extent that someone complained it was too bright and going in there window and it took a screwdriver and five minuets. The light was dimmed and redirected towards the road! Another citizen that can sleep happier! (I’m not the installer just an office bod loool) I must ask you to look more into smart city’s and the fact that some city’s in the world can now change the colour output of their lamps from a simple computer. It’s said to create a less volatile environment when tension is high! It’s really interesting and I’d think you’d make a great video from this.

Surprising amount of depth!

Meanwhile in Berlin, the street lamps are still powered by gas

I would prefer the led-lights at highways (if they are safer) and sodium lights when it's close to homes, so that people could walk (carefully) at the evening without having their circadian rhythm being messed up.

I'm old enough to remember what streets looked like with the mercury vapor lights. When I was a kid they were replaced with sodium vapor, and I have always hated the orange light they created. While the blue/green color of the Mercury Vapor lights wasn't great, it was infinitely preferable to sodium vapor. I'll be very happy to see sodium vapor go, and replaced with something more like white light.

how about we just use LED SPot lights to light the roads?

This is great! Can you do a “streetlights were blue long before LEDs” for mercury vapor?

Nice! Now you have to make another video talking about how CRI affects all of this!!

Leans in: "Our eyes deal with... the sun" Leans out. That was pretty damn hilarious... Quick question about VW's contribution, why would you want to street light during the day? Doesn't seem beneficial. Furthermore, I get these CREE bulbs from Home Depot that are Wink enabled which can change color temperature across the entire spectrum, as well as dim. The technology exists for sure.

Some parking lot lights use that brightening and dimming capability based on human presence. That could also help with power usage.

what about those self-recycling incandescent bulbs? what are their efficiency? i heard a few years ago that they even managed to outdo leds in that regard, with the advantage of being the best type of artificial light by almost any metric. i'm sure they are probably expensive and not really good for public illumination, i'm just curious about them.

Circadian rhythm my ass. All this fancy term means is .. we got used to sleeping when dark and staying awake when not. Pre industrial hunter gatherer to agricultural societies may had adapted to this. Not in a post industrial revolution city, where the work day never stops. The light bothering you ? Not letting you sleep? Buy or make a sleep mask to cover your eyes. Adapt or die. The name of the game. we adapt to the environment. Its unnatural to work nights, yet millions of people do it. From night guards to doctors, to anything you can name. We adapted. Jeez you'd think this was the 1700 the way some people carry on. Adapt to city life or.. go live in the country.

Highways and high traffic roads should be lit with cool lighting partially because of its circadian rhythm disrupting properties. The blue tones keep you alert and awake. As for low traffic, city, and suburban roads, warmer lights should be used to avoid circadian rhythm disruption and create a more pleasant atmosphere. Best of both worlds.

am i the only one who hates the blue-white color of the led street lights?i am much more confortable with the usual amber glow...the leds really bother me i feel like i can see less and concentrate less on the road

Erm but why are you even lighting the road at 4am in the morning? Just fit motion sensors to all the lights.. Done.. Plus that would be cool AF if you could run down the road and lights come on.. you could even do them in sections so they light up only where they need to, also this would be great for detecting hazards..

5700K is a lot more aesthetically pleasing for you ask me ! I HATE yellow lights at night, I really hope 3000K doesn’t get chosen as the standard, I’d be really sad.

I am on the 3rd floor (2nd floor in the UK) of my building and my kitchen is on the side of the building which has street lighting. I used to be able to open the cupboard nearest the kitchen window at night and get an item out by the street lighting only. What a difference the new LED street lighting has made...I now have to switch the kitchen light when I want to get something out of that same cupboard! The change was so dramatic the 1st night that I noticed it I thought all the street lighting was out...but no..the light was all going was quite amazing.

I'm genuinely shocked that I watchd almost this whole video. I certainly have never heard of the complexities of this decision before. Well done!

I'm not convinced that a lumens per watt comparison is enough to tell the story. One aspect that was not covered is LED's inability to "cast" or "throw" light as far as traditional sources. This problem has been replicated many times with halogen vs LED automobile headlight tests. You touched on the need to replace the whole fixture for optimal LED reflection housing but sometimes the entire light post should also be replaced. I have noticed that LED replacements on tall poles do not illuminate the ground as well as the traditional bulb. Would be interesting to calculate the price breaking point of packing in more LEDs (which would increase the energy consumption) in order to increase cast ability vs replacing the entire light post and lowering it to the ground. I think LEDs are great and have a wide range of applications but not entirely convinced they are appropriate for large illumination efforts.

You seem to be pushing your own aesthetics a little here? Personally I much prefer the bluer light. It makes me feel calmer and more alert. In the redder light I feel more on edge and nervous and therefore more likely to cause accidents. Would be nice to see some research on this rather than subjective speculation, but I understand this is outside the scope of your channel.

They should use yuji LEDs lol those things are like a fake sun

I've never really had a problem with the affected/effected issue. I probably just overthought it. Effects was the correct one in the context I had been writing from at the time.

The best solution would be to have LED street lamps with a 2700k or 3000k color, a warm white color instead of the 5k-6k lights thar are almost blue. But they are lazy and too cheap to use warm white colors so they save a few pennies and buy the cold white leds instead.

SteelSkin667: I think that may be what the environmentalists would want to not happen.. If migratory birds and butterflies use moonlight to navigate etc, making every light fitting a potential moon is a bad idea (highway lighting looking like a path of punctuated moonlight could lead the birds up the wrong path.). The idea of making highways lighting visible to non migratory wildlife may actually increase their use of our readily accessible thoroughfares, there may be unintended consequences - as with all human activities....

Seraphina S: 20mph limit is by no means universal in "suburbia" (not just towns)... Where I live 50km/h is common with 40 km/h in "designated areas" lol (politically sensitive and school zones). European 30 km/h zones are so frustrating ( in town centres and heavy traffic - one lane thoroughfares- yes you naturally go slower, but 24/7, nope.) for example...

fluffy_tail: Plenty of Uncivilised ones have shutters too.. lol..

TheLinkoln18 cough, Affected. lol (unless you are really triggered/controlled by it, then "effected" may make sense.) PS. not all nighttime light based disturbances are circadian rhythm related (necessarily), jut as not all "jetlag" effects are either.... I may find it hard sleeping with a 200W high pressure sodium vapour light on in the BR. jk..

Great book on the topic would be Mathew Walker's 'Why We Sleep'. No, the blue component of LED lights is NOT a good thing for road safety. Being exposed to blue light in the evening makes the time it takes to fall asleep longer and once you do fall asleep, the quality of your sleep is lower. But it does not reverse the physical and mental impairment caused by your body's need for sleep.

As for dimming, in my city at 1am only every 3rd street light is left on. The result ia still sufficient for pedestrians but very uneven lighting and of course the llights don't wear out not at the same time so probably maintenance got a little more expensive. I'm actually quite happy that the light next to my sleeping room is off late at night - but somebody else down the road will have to suffer the full strength of illumination for the entire light. So dimming would probably be the best solution. The CRI of sodium lights is awfully bad and can essentially hide thigs on roads. I rather suffer ugly blueish white than the monochromatic light of low pressure sodium lamps with the incredile CRI of zero or effectivly monochromatic light of high pressure sodium lights which in the typically used versions for street lighting have a CRI of just 25. There are versions of high-pressure sodium lamps with high CRI of around 80-90 which can be used for interior lighting or shop windows - but those types are less efficient and rarely if ever used for outdoor lighting.

with led street lights they also can vary the brightness which can save power. And make then turn off and on when needed.

Put 5700K LEDs on the highways and any high traffic non residential areas and limit residential areas and lower traffic areas to the 3000k LEDs or keep them HPS,

Interestingly, I actually find the orange light kind of unsettling. I also get that too blue-ish a light feels harsh. But I'm more used to "normal" (white?) light streetlamps around here, and when they had one of them be orange for a while I always hated walking under it, felt so ugly and hurt my eyes :P

you want the cooler lightes on highways to kee[p you awake and concetrating on the road

So, sodium is better for daylight lighting. An anecdote: Allan Dwan, who directed the first Robin Hood, was working at GE selling sodium lights for the filme industry when, in a conversation with Charles Steinmetz, mentioned he was not happy with his job but really liked going to the Hollywood studios. Steinmetz told him he should do what he liked, leave GE and go to Hollywood. Allan Dwan is one of the pioneers of the art and had a carrer of over 50 years. Nice video! Regarding the length: people still like to get all the information you supply.

LED's suck. They burn out much faster. CPS energy in San Antonio there LED lighting is UGLY, and burns out like Detroit's.Damn liberals.

White LEDs would be awful. Since it would destroy your night vision, which would decrease safety when you move from a road with bright white light into actual dark roads. Cyan-green LEDs at the lowest brightness to still be useful would be best.

I was a part of a Turtlewatch program for a while a long time ago here in Australia. The lighting of the surrounding areas was often confusing for a lot of the hatchlings as you say. Common practice was to guide them down the beach manually using torches (flashlights) to the water.

PS: There are also mercury-free sodium lamps.

The cool LED light makes driving safer in a short run, but in a long run it disturbs your sleep and turns you into a dangerous driver. You're a safer driver if you're kept awake by the blue light few hours longer, but you can't be kept awake 24/7.

Nowadays in many industrial buildings (in the Netherlands) inside lights are being replaced by LED. For people who must work in nightshifts this might be a biological disadvantage, because it signals the body to go to sleep? I am not sure about this, because I NEVER hear people talk about this. I only hear about the known advantages, energy saving etc.

As always, thoroughly researched.

I've noticed new police cars in my city with LED light bars. When they're running a random breath testing checkpoint, you cannot see the flashing lights on the light bar AT ALL when driving in the opposite direction. I think this is one of the best demonstrations of how the lenses of these lights can be designed to prevent "sky glow".

Interesting. I have always found that blue light is much harder to see at night than any other colour.

What about putting a filter to block the blue light on the lens of a 5700k led street light. You could get the efficiency of the led but not the effects of the blue messing with are circadian rhythm.

This guy is awesome. Love your content.

here's an idea: use 3000K LEDs in residential areas, and use 5700K LEDs on highways and freeways. You get the best of both while avoiding having too much blue light in areas where people are trying to sleep.

LEDs should be used around major highways where buildings are sparse but in neighborhoods, sodium lights should be used. Or at least amber lights. I wonder if street lamps had RGB lights instead where everyone could change color at will.

1:37 I took 88 home all the time to Aurora Illinois. Brings back memories now that I'm in Michigan

Hello. I like what you are doing here. Please, stop using the catch-all term ""Robust." I LOVE your videos, but the word "robust" seems to be a catch-all that my graduate colleagues use almost as often as they say "Ummm..." when speaking in front of the group. That said, I have lived near Mt. Palomar in Temecula, CA, and going out for an evening walk is like walking inside an old GameBoy. It is disturbing. If people live in the city, they need to understand that they will have to sacrifice pretty light for safety. I grew up in the desert, near Edwards Air Force Base, and out there we gave up things to live in the country. Everything is a trade-off, and I would rather have safe roads that keep me awake behind the wheel. The blue light thing is like those people that sold those "blue-blocker" sunglasses on TV in the early 1990's. It is the same stuff that has managed to find its way out of the chiropractor's office or holistic store, and into the mainstream. My wife and I are going to vaccinate our children, use cell phones/social media, and drive gas-powered cars. Your videos are good, and I got into your channel when I was searching BataMax on YouTube. I recomend you a lot, but I have no idea how many acctually watch, but thank you for doing what you do.

You are an excellent nerd.

As long as the lights have good optics that direct the light where it's needed - there's nothing worse than a white light that lights a tiny area under it and blinds you all the while, especially on a dark rural road.

I'm an electrician at an international airport in the Midwest, and the light pollution from our facility alone is staggering. I beg my bosses to get a lighting engineer involved in some projects, and it never happens. We install LED wallpacks all over the place that shine almost 90° from the wall (even large ones meant for wide open spaces are used for stairwells!), and they're distracting over a mile away. I try to educate how much of a waste that is, but no one cares. It's infuriating!

I actually prefer the look of cool led light over warn light

Just brainstorming here... Can the blue light be filtered? If so, why not start a new market for “night glasses”. Then can have best of all worlds... - biological impact to humans, low - lumens per watt efficiency, high - safety, high Maybe filtering these wavelengths will make it too dark, and lose all safety?

Another great video! When I moved to San Jose I was alarmed at the color of the streetlights! They're the same color as yellow traffic lights! But then I learned why, the Lick Observatory. I think you should also consider the maintenance and replacement costs of HPS (24k hours)vs LEDs (50k hours). When I ran the calcs for my house it was a no-brainer.

I think cooler light looks better

In my opinion You are a great presenter, and I find that I watch with interest subjects that I otherwise wouldn't give a passing thought. Thanks for another enjoyable video that also made my "general knowledge" a tad wider. ((P.S. I seem to remember having been told that one "reason" for using the LowPressureSodium lamps were that their "relatively long wave length" made their light better suited for conditions with "low visibility", when arguably the need for lighting can be said to be at it's peak. The argumentation was something along the lines that "whiter light" made "Fog//heavy rain or snow" more "opaque" to the driver. I'm not certain whether the argument was basing this on some quality of the light, or some property of the human "visual system" or some combination of the two. Was this a "theory" that came a cross while You researched this topic ?? D.S. ))

I am wondering if you will get into why in some state here in the US and a few countries around the world. Started using Blue LEDs to help curve Anti-Social Behavior. In fact, it is a tad amazing that the color change does work. As there had been many studies that showed. These Blue LEDs had drastically changed moods at night by a pretty large percentage. Note: This is BLUE COLORED LEDs not Blue Light LEDs.

9:45 I work in a building in Manhattan that has exterior lighting to light up the facade at night and it's incredibly annoying when you're inside the building at night and the lights are literally shining into your office.... but god damn that building looks fantastic from the street!

The city of st pete fl installed those on my south side street. Looks like a Hollywood filming studio.

The UK uses timed lights and reducing output system, so it is available; the US Federal Highway Administration just need set regulations to allow it so states can try them out.

Take a drive through the Chicago neighborhood that have gone to LED's. Chicago has settled on 3500k light heads.

As a resident of a city that completely converted several years ago let me tell you, LED streetlights are TERRIBLE! the light output is dim and direct which creates huge dark spots in between the light poles. Our residential streets look dark and frankly spooky. Would discourage any other municipality from converting.

LED street lights on highways, freeways, and other roadways that don't border living spaces seems perfectly fine. The problem is when you fuck with people in their homes during the night.

id say the light disrupting the sarcadium rhythm, in this case, is actually a positive. The bluer light should help keep drivers more awake. So LEDS should be the all around better light on roads.

When it comes to the circadian rhythm disruption issue, I think there could be a pretty good compromise solution. High traffic and high speed roadways could use the cooler lights for added safety, while low speed residential streets could use the warmer lighting to limit sleep disruption. Since drivers will be moving more slowly in those areas anyway, it isn't as much of a priority that they be able to see as far or have as fast of reaction times.

You ar ful of

It seems like a good compromise would be to have the higher-temperature lights in non-residential areas and highways, and stick to the lower temperature LEDs or HPS lights in residential areas.

The issue with white lighting on highways is that it messes with night vision. It's fine if the highway is lit the whole way, but moving from lit to unlit and back again is tiring. Also as you mention it's down to the heatsinking and driver design if they're good. I think the issue isn't well discussed enough in street light purchasing. I've seen a lot of LED lamps with blown chips and failing drivers only a few years after installation. Driver cooling needs to be better thought out to prevent the caps being cooked.

I love the colour of the LED. I think blueish light is beautiful, even if I still like the yellowish HPS.

Honestly I had you categorised has an uninteresting fool. Well if all you say check out( and yes I'm going to check it) I will actually be interested and I might even recommend your chanel. Keep up the good referenced video. Ps: iv always avocated shut down of all outside lighting after 22h00. anything beyon that is just usles crapy incompetent city management.

Your audio quality hasn't improved and has actually gotten worse at 480p compared to old microphone.

Laser lights maybe? :O

The thing about blue light ruining your vision is a simple misunderstanding. Blue light ruins you night vision, it doesn't damage your eyes. However, that brings me to the one thing everyone seems to be missing when talking about street lighting: Night vision. Or in other words: The capability to see things that are not directly lit by street lamps or headlights. I still remember the time when you could drive on an unlit street and actually see things outside the small area your headlights and the headlights of other cars light up. With the modern hi-power white lights that is almost completely gone. (That modern cars try to blind you with their instrument clusters doesn't help either...) You mentioned LED lighting being smoother than the older lights, not quite as spotty with areas that get less light. That actually is a bad thing. The changing light conditions help our depth perception to work when there's no single light source (sun) with its shadows. The smoother the lighting, the more the brain has to rely on relative sizes of objects. Something it actually is not very good at, even more so because cars come in many different sizes.

would not the blue white ligth mess more with our nigth vision, than the yellow red ligth an therfore let us se better in the unlit areas?

Our irises are wide open at night and our cone and rods are tuned for seeing as much blue as they can get blasted with oncoming blue headlights. That makes us deer caught in the headlights while driving thousands of pounds of metal everytime a car goes by.

10:04 That's typical of LED lighting in the UK too. Dark, light, dark, light. It's useless.

Thank you for addressing the sky glow problem. All that is really needed is a shield to direct the light downward. This will reduce sky glow by 90%. Residential outdoor lighting also needs to be addressed.

Blue light damages the eyes .

Dimly glowing roads and sidewalks could work in some areas. See shadow-dodge shadow would be some thing to train for however.

HPS is less visible and puts people to sleep behind the wheel. Get rid of them! Use 5K Temp LEDs!

+Technology Connections — Your use of the "cooler lighting" term is confusing in places. Do you mean lower Kelvin color temperature, i.e., shifted toward the red end of the visible spectrum, or bluish light, as from "daylight" LEDs and "cool white" fluorescent tubes, which actually produce "hotter" lighting, according to the definition used by physicists?

it sounds like the blue light fear camp is based on the original issues with flicker from fluorescent lamps that cause the iris to expand and constrict to try and compromise for this flickering, which causes the muscles in the eye (iris) to wear out so to speak. as muscles can be torn by use, destroying muscle cells, and thus require cells existing that are still alive, to split and divide losing some of their telomeres shortening the hayflick limit distance to ending their life span

You may also may want to note that a 3000k color temp will be closer in matching the output of halogen headlamps while 5700k is closer to the LED and HID types.

Another awesome video. Thank you :)

We have those CREE street lights at the university I work at. I'm in the electrical department. Our sky glow is actually worse with them than the HID lights we used to use. The issue is that equivalent lumen fixtures are generally purchased at higher color temps. Believe it or not the reflected white light from these led fixtures washes out the sky worse for telescope viewing of the night sky. The color is also impossible to filter out due to the wide spectrum of it. I forget the wattage but the temp is 5K. I also have them outside my house and yes, it affects my sleep.

You are wrong. Under night conditions your eyes are blinded more by the blue light, cannot SEE things better with it. This is also when it is low level light, not so much light that it is essentially nearer a daytime level of light, not on a linear scale but rather log because that's how the eye perceives it. The correct solution is to stop using LED lights in the colder color temperature and move to high CRI around 4000K. Your associating moonlight fails to take into account that it is harder to discern depth, and colors. Why are colors important? They are a very important aspect of identification as well as reading signs. Of course you can still "think" about what you see and identify it but having to do that continually means a less optimal driving condition. Now stop and consider what happens when your eyes are more "sensitive" to bluer light. Your pupils contract so you take in less light. Everyone has experienced the phenomenon we call "glare" and whether you want to admit it or not, glare is not productive to seeing things. Please a little common sense. Have you never seen driving glasses? They are yellow, not blue tinted to produce a warmer color temperature, and no they are not for daytime use. Do a web search if you like, these yellow tinted glasses are for night use. I know it's hard to believe but this has been researched for longer than you've been alive. Maybe consider researching without the tainted opinions of those in the LED lighting industry that just want to sell lumens by offering product in the colder color temp. Even if you don't want to consider research, there have been many comments in recent years about how harsh and more difficult it is to drive in areas with these glaring cold LED lights. Did you think people were just imagining they couldn't see as well? I can assure you that it is not the case, people are in favor of seeing better.

I think the blue light thing is because it can make your eyes sore?

I had cancelled my Patreon donation to this channel. I feel regret about it now because the videos are good and informative. I will re-establish my donation again. I had not viewed any videos for a small while and now I realised what it was that caused to be donate. Good job.

If you're falling asleep, pull off the road and take a 15 min nap. Period

20:41 "GET IN THE WATER WHERE YOU BELONG!!!" Alec screamed as little turtles scrambled across the moonlit beach.

I prefer sodium lights. We really don't need EVEN MORE blue light in our environment… like we already have with CFL and LED lamps everywhere. Nothing is more calming than the nice orange glow of the streetlights at night. Also much better for night vision. Monochrome light or not, at night you don't HAVE to have 100% accurate color representation but only NIGHT VISION.

Do we really need to see the night sky? Also people can just get curtains to block it out of homes. I also thought movement detectors could be good to only emit light when a car is passing by. Perhaps one lamp signaling the next 2 or 3 to light up ahead

Well researched and interesting. Bravo

I'm all about lowest energy to get the job done. Imagination the energy savings over time.

How is it that the "cooler" colors are the ones with higher color temperature? I remember studying black-body radiation, and it seems crazy that the coldest - literally - colors of light are commonly called "warm" while the hottest colors are called "cool". I wonder if the same thing happens in other languages.

So we should sacrifice our circadian rhythm so cars can drive at higher speed... Personally I find this quite dystopic.

Have you looked at green LED lighting? I see it reasonably commonly used as lighting that is supposed to reduce light pollution.

The blue light from LEDs can be a strain on your eyes but I do appreciate them at traffic circles and back roads when driving at night. But for highways I think the lighting should be a warmer color temp but at higher lumens.

A very deep dive on how to rearrange deck chairs on the RMS Titanic. Hopefully soon we won't need so many street lights as we get drivers off the road, especially at night. And I'd much rather live somewhere that distributes free flashlights, letting me put the light where I need it, than somewhere that spends 10x as much shining lights into my bedroom window.

Even if you believe in the circadian rhythm disruption theories, (I don't, it just feels like more anti-cell phone technology bashing to me), wouldn't you WANT people driving at night to be more awake and alert?

Hah! I'm used to living in cities seeing nothing but faint stars. So experiencing the full scope of uninterrupted space at night when in rural areas is indeed a scary thing.

Good to see Jay Foreman is supporting you on Patreon! Although I agree on LED being a lot more efficient in energy terms, and LED’s fixtures may reduce light output contamination, Sodium Vapour lightning systems and fixtures are wonderful, even the bulbs themselves are beautiful (LPS ones are specially interesting), the warmup process is so pleasant to watch and from my perspective I found that amber glow so pleasant, making some atmospheres more introspective, like in the streets of Rome. But well, perhaps we have to face progress, although white-blue LEDs are the most horrific thing in the world!

at 14:40 I like the cooler light better, I have never been a fan of the warmer yellow tint light.

Light pollution is a problem pretty independent from the actual light source used. Only LowpressureSodium can be effectively filtered. And for all lamps it really helps when the fixtures is designed correctly as to not waste so much light and to spread it evenly and for that it would be important to INCREASE the number of lamps used: Smaller distance between lamps would mean less falloff and smaller brightness variance. About the perception of brightness of different wavelengths: The ratio between energy and perceived brightness doesn't change much. It is simply that under the sensitivity of the cone cells drops of sharper than rod cells do. So it really depends on exactly how bright the lamps are when talking about the perceived brightness/watt. As far as i am aware of in most countries the regulations put the minimum brightness that the streetlights need to provide at well above 0.5 cd/m², more often than not it is above 2 cd/m² - well above the scotopic range, mostly just mesopic and even "normal" photopic. And there the sensitivity of our eyes is still great for those wavelengths - so that advantage of LEDs is only there if you have really dim lights only.

I seriously dislike LED street lights. They are to bright if you have the poor luck of having on in your field of vision. I also have questions about how much of that higher temperature sensitivity remains when you are dealing with older people.

I'm not sure circadian interference is a problem on highways - pushing drivers more into an awake state seems to be a rather positive thing.

Here in the Detroit area, the street lighting was owned and run by the city, independent of the local utility company (DTE Energy) They were many large areas of the city and neighborhoods that had gone dark due to failure. It was decided in conjunction with DTE to totally replace all the street lighting with LED’s. I believe Detroit is largest city currently lit by LED. There’s a picture of Metro Detroit taken from the ISS and it’s quite evident how the city stands out in comparison to the suburbs, in light level.

could you please cover those greenish coloured lights that are appearing in various places, too?

Superb content quality. Depth and attention to details is especially appreciated. If I had spare money I would have supported you on Patreon, but we're kind of really struggle to survive here in Russia.

The possibility to dim LED lights is a huge bonus. I have seen *street lights* in resedential areas here in Austria which have a *motion sensor built in.* They must be *using radar* to do that. They react to pedestrians and cyclists as well. They get alot brighter when you approach them and dim down again after 30 seconds to a minute. This not only saves energy, but reduces light polution (obviously) and will extend the lifetime of the lamps and LED drivers. For fast moving traffic (where a motion sensor would trigger too late) lamps could be connected and relay the information of a moving vehicle ahead to do the same thing on highways for example.

Moonlight is not "blueish", it's 4000K, as opposed to the 5000 to 7000K or so light during the day time, it just appears blueish because the level of light is very low, and as you said we pick up shorter wavelengths better in such conditions. It's interesting that the study you cite actually has different results to that done by Philips in France, regarding CCT preference; 4000 and 4200K sources both ranked below 2000 and 2150K HPS, with 2800 and 3000K being the most preferred option.

u need a new blazer other than that keep it up!

While it would be more efficient to use 5700k light superficially, think of the additional strain on the food supply and public utilities from all the hoardes of sleepless masses puttering around their homes, with disrupted circadian rhythms ! I too recognize that I can see better under blue light , but the harshness is borderline aggravating , because I can feel the light restimulating my brain. It's like drinking coffee before bed if I'm driving at night . I will miss sorely miss HPS

He said Please, how can I not sub???? :D

You live in Illinois too? Sucks doesn't it :(

So limit the blue lights to areas with little to no housing and use warmer colors around areas with lots of houses.

We should have auto dimming LED street lights that are motion activated for pedestrians and cars, like they have in Norway! No need to light the night, light the path as needed.

fluffysnowcap I just wanted to say, I hope this is the only time I ever see "areas" spelt like that.

I wonder if that's why my streetlight was shot to bits by an unknown sniper?

Technology Connections close your blinds then.

I really hate those yellow lamps on the streets, i can't see almost nothing clearly.

Thank you very much for this super interesting video! Even though I agree with most of what you said I have some things to add. I think it´s a bit sad that you did not mention that LEDs with their much higher blue emission attract insects way more than for example HPS lamps. Considering that insect numbers are free falling in Europe this could become even more of a problem as they get drawn to the lamp an die there. Furthermore this adds to a higher maintenance cost as you have to clean the fixture more regularely to remove the dead insects. Another fact worth mentioning is that in rural areas 50% of the light pollution is produced by secondary scattering. Considering this LEDs could increase skyglow a lot in rural areas as their blue lights gets scattered way more in the atmosphere thus increasing light pollution. A downside/upside of HPS lamps is that their light gets scattered less in atmosphere thus creating skyglow farther visible. The upside of this being that especially in regions with a lot of fog HPS lamps show a wider illumination than (for example 5700K) LEDs as their light gets scattered less. It´s right that LEDs could lead to less energy consumption IF they were used with less power than HPS lamps. Unfortunately most regions don´t consider the difference in scotoptic intensity of HPS and LED lamps and just use the same wattage of LEDs as they did for HPS lamps thus increasing light pollution. Another important aspect to add is that the bluer light of tends to glare more therefore reducing security again because the eyes have to adapt first. LEDs (especially with lenses) have a much higher surface brightness and therefore distracting drivers more. Another problem especially in less developed areas is the problem of wrong mounting. LED fixtures with an ULR (upward light ratio) of zero often do not get mounted perfectly horizontally. Because of this even a lamp design with no light escaping upwards doesn´t help much as the light gets directed upwards due to wrong mounting. Even though amber LEDs are great if you want little light pollution they have the problem of a super low efficiency (about 30% less than for example 3000K or 4000K lamps) and this value isn´t even regarding the different scotopic sensitivity of our eyes. I hope that I was able to add some new infos and that a lively discussion on this topic will start.

If only our government could project such data and results to us like you. They don’t say shit and do whatever they want

this video is just awesome !

I also read somewhere that the "yellow" or warm lighting is used in common fog areas due to its ability to allow the light to reach further to the ground instead of being reflected like the LED's or cooler lights.

Hey tech connections, I love your work and have been a fan of yours since around the 20k sub Mark! I just uploaded a video that you might find interesting. I have a LIFX, a smart Led that can be controlled via smart phone to change the schedules and color. The iPhone 8 + has a dual lenses camera, and it produces and unique effect on the phone. I thought you might enjoy looking at it!

It seems to me that if the lighting used a wavelength around 525nm then it would provide a good level of response for both day and night use.

Well researched.

I live in a city where the mercury lamps on the peripheral roads have recently been changed to LED, but the main drag still uses HPS. Also, I do get a little bit of sky glow from Osaka beyond the mountains to my north. Speaking of sky glow and energy savings, LEDs have the advantage of being able to turn on right away, so you could hook up motion sensors to them so that they’re only on if there’s someone passing under them. When there’s noöne there, they shut off to save energy as well as prevent urban skyglow.

Is there anything you _don't_ know, or want to know, anything about? I absolutely love the in-depth nature of your video's. Keep them coming!

We have had our suburban street lights replaced with LED (New Zealand). They are just damn horrible! I'm not sure of their K rating but, less coverage, too intense, they just look shit!

You should have gone into total lifecycle cost comparison.  How many hours can you get out of sodium vs. LED?

So I should probably use blue lights for all my outside lights...

I always wanted a lighting fixture hooked to my thermostat and other house censors. It would have 4 bulbs- a UV plant bulb, a IR heat lamp, some LEDs and some incandescents. My apartment used to always run warm. I had 4 track light incandescent flood lights in my track lighting. It was great in the winter. I was lousy in the summer (but not too bad, since they came on later with the extra daylight.) What I'd prefer is LEDs that run when it's warm, incandescents that run when it's cold, heat lamps that run when I'm getting out of the shower (probably just the bathroom and bedroom) and plant lights that would detect that I'm in the room and stop trying to sunburn me. (The laundry room is next to my apartment. People walk by all day so to get some privacy I have tons of plants in the window.) Throwing something in that changed the lighting depending on the time of day would be great too. I usually can't get to sleep until 3 am, and that's after taking a sleeping pill at 11 pm. (If I don't take the pill I don't get to sleep until 6 am.) My bathroom has 6 bulbs. It would be great if the light switch turned them all on during the day but only turned on 1 or 2 of them after 9 pm or so, if my track lighting could turn off/dim individual lamps linked to a timer, my computer could switch to night mode... I also think I have an idea for an improved privacy treatment for windows... a brighter layer between the pains to make it harder to look in. (Okay, not great for light pollution, but easier than automating my blinds (weird sleep schedules and plants that need light), and much cheaper than those press button to turn dark windows.

I have no idea how this ended up on my recommended videos, but actually it was pretty cool!

Seems like we could use both kinds of LEDs, blue on major roadways (multi lane, 45 mph and above, interstates). Warm LEDs in residential areas.

Okay so each kind is good for different situations. Apparently there isn't a single light source that we can choose which is best on balance. Replacing everything with LEDs sounds like it may be mistake. And it sounds like the previous replacement round was possibly a mistake as well. So why not use all of them where they are best suited? We should have it in a gradient of lighting according to our needs and wants for the situation. We want people to see hazards better and faster and we don't want them getting tired on interstates, freeways, and highways. So we use the LEDs there. We should also use those in shopping center parking lots and any 4 lane roads that are just busy streets and not highways. The exception should be public places where you might be sleeping. Truck stops, Rest stops, Hotels, Motels and shelters; Those should all use high pressure sodium with flat hooded lenses. Same thing for surface streets in residential neighborhoods, where there is less traffic and people are close to home (where they would also be sleeping). The low pressure sodium lights can be used for beaches, airports, observatories and anywhere else where you need to be awake, see well, but want to make as little light pollution as possible.

Great Video! and please check your audio settings or configurations it could be a lot better. Best Regards. :)

Amber lighting being less attracting to bugs has been known for a long time. We had the amber colored incandescent lamps on our porches in the 1960's. Of course, the color temperature of these made the entryways less attractive and these bulbs slowly went out of favor. I bought the latest solar walkway lights and I removed the white LED with an amber one for the cabin pathway lighting to the outhouse that has amber lighting inside. Sure enough, when I turn on the white LED flashlight, here comes the mosquitoes and mayflies! Anecdotally, I am hearing things from my fellow amateur astronomers that the LED lighting replacement areas have worse skyglow due to more reflection of streetlights off of the streets and sidewalks.

There was a study that I'd have to look up, recently of I think Edmonton. While the LEDs don't produce more sky glow individually for the most part, in new construction areas a significant increase in the number of lights are being built nullifying any light pollution benefit and actually making it much worse. I don't know if this is because Planners think they need more lights because the overall light put is lower even though the usable output is the same or greater or because the running costs are lower they over illuminate. LEDs are actually creating more not less Light Pollution due to the way they are being implemented.

My answer is yes no matter what you say.

I think the sleep part shouldn't be a problem. You shouldn't be tired while behind the wheel. So keeping people awake and alert is a good thing. Plus, people tend to not drive home and sleep withing 5 minutes. Instead they would drive home and relax for at least 30 minutes, which is enough time to fall asleep.

I've NEVER EVER EVER found a LED lamp that really lasted the number of hours or cycles it guaranteed it would do. The box says 17000 hours, but using most of them in a light with a timer I can easily figure out that they usually break after an average of maybe 7 or 8 thousand hours. And even if they don't just go off or start flickering, they get noticeably dimmer after one year of use (being on every night all the night). Surely they test them in very cold conditions, but where you use it it gets pretty hot in the case of the lamp even if the ambient temperature is freezing.. I've tried cheap brands, expensive "good" brands, buying them online, buying them from electric hardware specialised stores instead of the supermarket... it doesn't make much difference most of the times. They're all largely overestimating their durability. So I don't believe that 99% efficiency after 100.000 hours crap.

You forgot one big issue: Blue rich lighting at night has much more painful glare and EYE STRAIN. I have to wear sunglasses at night through roads heavily lit with cool white LED's. Thats not safer if you're having to squint from all the glare (or wear sunglasses). I have the same problem with oncoming cars that have cool white HID or LED headlights. The small point source from many LED designs don't help either. I can stare straight into a 180w low pressure sodium fixture at full brightness from 3' away and it not hurt my eyes (even HPS isn't that bad). Try that with any cool white LED (3500k+) of similar adjusted output and see what you get, you won't be able to but for a second before you cringe and look away in pain. If the point is safety then my point is road lighting and vehicle lighting color temps/types should be in a region that affects our night vision less as not everywhere is lit with road lighting. Orange is close to red which has a low effect on night vision. It is less efficient, but the transition to/from a dark to well lit HPS area is less harsh than dark to a well lit cool white LED area. The sharp cutoff of LED lighting also causes great areas of lighting contrast when not properly implemented, which unfortunately is often and a phenomena that you observed on the LED lit highway. I've been through countless retrofitted neighborhoods where I live that had DG HPS cobraheads that did a decent job lighting the street directly replaced with FC LED fixtures. They now have a nice bright 30' circle of light with everything else pitch black until the next light 60-90' down the road. Yes DG is less efficient, but it allowed for some margin in case the install wasn't ideal. You hit the nail on the head with 3000k LED, it is the way! Less blue light, less painful glare, less fatigue. They went completely with 3k LED in a upscale downtown area near me and it looks fantastic! It even is slightly nostalgic since 3k is close to incandescent as well.

I’m team orange, anytime after sunset all artificial lighting should be orange/red.

Poor turtles

I can see the milky way and the moons of Jupiter with my naked eye any night it's clear. Because there are no street lights for miles.

I love you for making this video. Thank you.

Here in Canada, many of our lights are already replaced with LED lights. we even have solar powered LED street lights where older lights woulent have been viable because of the requierment of power.

In my city we had alot of LPS for the neighborhood street lighting which was very nice. The light went right where it was supposed to and didn't shine into people's yards or windows that much. The Major streets had HPS with flat lenses and they worked very well. A couple years ago the city underwent replacement of all exsisting light fixtures to LED ones. They're on pretty bright at night but right at midnight they are dimmed to I believe 50% power. The lights communicate with each other over Wi-Fi which is pretty interesting. Now because my city has the U of A observatory on a nearby mountain they had to be very careful with what LEDs to use. I believe they are using 2700K lights. That low color temp and dimming at midnight were all requirements from the University. Same goes with the flat lenses used on the old HPS lights. Personally I hate the new lights and would rather take back the old LPS fixtures. Another thing is i have seen a ton of these new ones die iness than a year. The light dimly turns on then off again the entire night. If you're interested in doing more research on this subject the city is Tucson AZ.

I love how informative and concise your videos are. Commenting because I was only half paying attention when I heard the line about turtles making it 'to the ocean... where they belong' and it sounded hilariously turtle-ist :)

there's a reason modern smartphones and monitors have low blue light mode. Blue light is bad for health. Excessive use of white LEDs will lead to health problems.

This video misinterprets data. Blue light destroys your night vision more than red or green. Yes you can see blue light 'better' but then you are blind to all other spectrum.

LED is fine if you keep it between 2500-5000k. The white/blue ones are blinding.


LEDs should be same color as sodium vapor

Re:circadian rhythms - Do you really want night drivers falling asleep? Light therapy helps a lot with circadian rhythms, and most night-time drivers don't spend enough time under the lights to have much of an effect - especially with the correct light color at home. As for the 'high-efficiency' HPS - are city councils REALLY going to pay the premium price for them? Probably not.

The last house I lived in the street light shined so bright in my room I ended up having to buy black blinds so I could sleep at night. The light was not the yellow or blue but seemed to be pink to me.

I'm surprised that you complain about the aesthetics of LED blue-white outdoor lighting. I find the light, if a little cold, absolutely wonderful for driving under. I also find it an enormous aesthetic improvement over sulphury-orange HPS lighting, which I can only describe as "horrid." Perhaps I'm wrong, but I think a strong majority of people would agree with me on this. Also, I'm not much concerned about potential melatonin disruption of LED street lighting. Few people come in from a long drive and jump into bed immediately. The one hour or so one spends unwinding from highway travel before bed at home should be time enough for the body to shake off the blue-white light--provided one hasn't flooded the interior of one's own house, the bedroom in particular, with blue-white light. I've experienced the sleep-disruption of blue-white light, and in my case, it was because I installed "daylight white" LED lighting in a reading lamp I was using before bed. I changed the light bulb, but what I found was that if you stay away from blue-white light for 60 to 90 minutes before bedtime, it's not much of an issue. Ergo, I don't see blue-white LED street lighting being a problem for the vast majority of people. To my mind, the potential melatonin-disruption issues experienced by a small minority of people are outweighed by the increased driving safety the lights provide for everyone. Lastly, I enjoyed and appreciated your commentary regarding light pollution. The footage you showed of lighting from out the window of an airplane was absolutely great. I wish every town and county that was in the process of replacing their street lighting would watch that portion of your video. Thanks.

Is that a KALLAX shelving unit in the background?

Wtf, are you sleeping while you are driving? Warm light is good for your home, cool light is perfect for security and street lights. Driving is not about "astheticly pleasing".

Only one highway near me - the Ely Link Road which is a 4 lane dual carriageway running through a cutting - uses large-scale LED lighting. It's a perfect use case for LED replacement as the road runs in probably one of the largest cuttings in the UK, and passes only one housing estate which already suffers greatly from the irresponsible development next to a very busy, LOUD highway. The increase in my percieved light and also the reduced light pollution is exactly as you say - I love it and want more!

Scotopic, mesopic, melanopic..... If only you had spent some time describing these terms before heading off into video where these terms appear in almost ever y other sentence.

Love me some white LEDs which are actually blue and damage your retinas.

And also there's a reason those BS fake xenon bulbs which are blue are illegal.

Just switch to xenon and be done with it. I will never own any car which does not have xenon headlights in a projector housing.

Though I'm a bit dubious about the blue light scare myself, I can tell you from personal experience: Don't stare directly at a high-power blue LED for very long. I was working on a project that used a 3 watt blue LED chip and a remote phosphor cone to make a white light source with an even dispersal. I had a spot in the middle of my vision for the next 24 hours, after looking at the blue LED for only a few minutes. There's also the problem that blue light scatters in the atmosphere more than other colors. It's the reason our sky is blue, and it also means that pollution from blue light sources travels further, even on a cloudless night.

Great job on this! I'll have to watch it again to assimilate more of the material!

No need to abolish HPS, or for that matter - have a single "one size fits all" solution. For instance, keep HPS for residential lighting to minimise circadian disruption, go to cool LEDs for roads. You WANT circadian disruption here, reduces likelihood of drivers falling asleep!

The real question is: Should /you/ light the way?

I think LED lighting should be somewhere in the middle between the harsh cool light and the warm light you showed in the video. LEDs are available in a lot of different color temperatures, not just the two extremes.

i like led street lighting. i work at an airport just west of you and ups changed their lights to led and amazons ramp still has hps. its so gross working under the hps lights. i hope they change all the lights. though ive seen all the old hps fixtures in a pile in ups's graveyard and id like to get at some of that metal lol

So, is 4000K the best compromise for street lighting?

One thing I wonder about is if the Warner light may do a better job lighting the roadway in fog or other inclement weather.. I generally also prefer the more blue color of most lights.. I definitely see better in that color. But it is rather harsh . Also.. I never believe the marketing about the longevity of LED's. I have a few Cree bulbs I bought several years ago.. they were pricey then.. about $10 per bulb. Very bright, but honestly didn't use much less power than the equivalent CFL.. All of then have now failed.. at way less than the 20,000 hours or whatever they claimed. And they were a "quality" bulb . I now use the budget brand from Lowe's or Home Depot. They are about 75% as bright and 25% the cost. Great and interesting video.. Thanks for posting

Great content thanks. I remember my trip to Hawaii in 2001 and hearing from the locals that there are special laws in place to prevent light pollution due to the observatories. The view of the night sky was spectacular yet the roads and parking lots were well lit. I would guess that the observatories are having a tough time of it with the volcanic eruption currently taking place.

solution for skyglow? plant trees by the side of the roads?

Well written, great information, good delivery.


Saying it is safer for drivers is very short sighted statement. Drivers, who do on long trips, or drivers who spend a lot of time on the road, like taxi, would get disrupted circadian rhythm, which has curious side effect - not feeling tired, when in fact you are, thus reducing alertness and not only negating "safety benefit" but endangering even more people

illiteratebeef nope. Being sleep deprived is just as bad as being drunk

I disagree with that, I’m not going to drive while tired, and if I do get a little fatigued from driving long distances, I’ll stop at a service station or lay-by and step out the car for 15 minutes and take a drink. The only difference to me is that my eyes hurt when I arrive to where I’m going, and seeing as the light is more directional, it creates a flashing effect at the top of my windscreen as I drive under them, which is also very annoying and disrupting.

A bonus to cold lighting in roadways is people are less likely to fall asleep at the wheel as well. So I think the blue lighting further increases safety.

Why does it seem to me that I see better in the yellow spectrum? I don't seem to be bale to see that well with the 6000K HIDs but get me behind a 4300K or a 3000K and I do much better. Maybe it's just that I have odd ball eye balls? Thank You for the video.

Sir, you forgot to mention foggy and snowy driving conditions. Blue is blinding while the amber's wavelink cuts through. (Car fog lights are amber.) In the 80's the old bluish lights were switched for the amber and it was a Godsend for those conditions...

The city of Calgary, AB has replaced nearly all of their LPS lights with LED street lamps. Incandescent traffic lights still remain, but pedestrian signals are being replaced by LED

Just remembered that I haven't seen a sodium lamp since like 2015/2016 in the city (1.3M People). But I digress...

Where I grew up (rural area) they still have the old white lighting. I always preferred that to the modern sodium lighting, when it rains the effect with the sodium lights is hell on my vision

Did not discuss filament style LED which are presently starting to get common. Granted they are still a long way off from producing high lumen and wanted design.

Yanive had more night bird strikes since I've replace inc. with led. Perhaps I should invest in more bird friendly lighting.

Windsor Ontario used 4000 k leds. Only major intersections used 5000k to improve visibility. Once both Detroit and Windsor switched to LED the sky is now dark again.

You are thorough and compelling! Now perhaps we should talk about extra ultra bright headlights on cars - especially ones lazy people leave on all the time to a) deter the police from reading their front plate and b) using the automatic setting since it's so hard to turn on lights when it's dark or crummy weatherwise. (I could mention my 2012 car which lights up the dash at all times, removing my main way of checking if my lights ARE on, but I digress...)

We clearly need RGB streetlights.

[17:10] You started off with saying you found it displeasing. Next time, you said others could find it displeasing. Now you say it's displeasing overall, like it's a fact.

Anyone driving at night enough to have street lighting affect their circadian rhythms already have messed up circadian rhythms.

I love your videos on street lighting! I have started to become borderline obsessed with it myself, I am even starting to collect some old HPS fixtures. I am hoping once IDOT replaces the GE M400A1's on I355 or I55 I can get my hands on one. There is something about the cutoff design and retro look of them that fascinates me to no end. One question though, I noticed around Route 83, I290, and I294 there are GE M400A1's with little red circle shaped devices attached to them just under the lens on the ballast cover. They are quite obvious, and it seems the newer replacement GEM400A2's don't have them. For the life of me I can not figure out what those are for even after hours of research. They don't seem to be a photocell since the fixtures also have the top mounted photocell. It just struck me as fascinating since only around the Chicagoland area have I seen the little devices on them. I do wonder if IDOT did some funky custom addition back in the day when the fixtures were new technology. My only thought is they might be an indicator light of some sort. Let me know if you have an idea of what they might be!

By the way, could make a video about light color and lamp types in car headlights? The benefits and drawbacks of 3000K, 4300K, 5000K and above temperature color and halogen vs xenon vs LED. I've been using LED in my car headlights for while. The first chips were big, inefficient and lacked focus on the reflectors of my Fiesta Mk5. After some tests, I reached the conclusion that the smaller size of XML-2 chips and the high efficiency of these chips were the way to go. On the next test, I proceeded to pick up a set with theoretically bigger, more powerful, slightly less efficient and bigger (which should ruin the focus a little bit) XHP50 LED, but I noticed that the focus was as good as the XML-2 and the extra heat wasted by the system was actually useful to heat up the lenses of the headlights and remove fog and moisture that could disrupt the focus of the highlights and blind people in the opposite side. I guess you are very knowledgeable about the light subject and could probably make an interesting video about it. Thanks for your video. It was very didactic and informative. ;D

I think a good mixture would be to have cooler lights on main thoroughfares and commercial areas, and warmer lights in residential areas.

The number one issue with people changing lighting to LED is that they are usually way too bright for what they're being used for. The state changed to white LEDs on our main road, and it's oppressively bright and much more distracting. I'd hate to have to live in a house on that road.

Blue light is the worst for sleep. I can recall endless times when a blinking blue LED in my room prevented me from sleeping. The thing is it didn't even output a ton of brightness, but the only way I could sleep was to use masking tape to cover it up. Maybe slow-blinking blue LEDs can be used as an alertness aid for truckers, or a more focused blue light can be used in a way that avoids a lot of light pollution but I know I wouldn't want any kind of bright blue lights entering my window from the street lamps outside.

I still don't know what Sony was thinking when they made the backlight in my alarm clock very vivid blue.

That's also the reasons why some phones have 'night time mode' which reduces the intensity of the blue colors on the phone, because cool blue colors interfere with melatonin production and can interfere with sleep.

I think the circadian disruption effect of LED lights is actually just another advantage: it keeps people awake behind the wheel

I feel like I've been ran over by a million little nerds in dapper jackets

Thank you for an incredibly interesting video. So many things to consider when using artificial lighting.

As for LED causing sky glow and affecting observatories - Who says they have to be white LED's? Most colored LED's are almost monochromatic, so yellow LED's could still be filtered.

You have made an otherwise uninteresting topic, interesting! Thank you fellow i88 brother. I probably shouldn't have gotten excited to see highland ave...

Keep your sunglasses in your door pocket or an open center container where you can reach swiftly without much thought for driving under harsh LEDs and of course sunlight. If they're optimal for everything else considered, wear sunglasses if they bother you.

I think the use blue light sources should be banned from street lights due to light pollution and the effects on wildlife.

I feel enlightened now and after all this also a bit suicidal!

The winner is 5700K blue LED light. That looks 1,000,000 times better than those orange crappy lights. The comparison you put in the video is night and day...pun intended.

The new bypass being build around my city has 4000k led fixtures installed around it. Much better then the HPS and the light is very direct and not much glare.

Don't forget the disruption of the circadian rythm caused by LED lighting has been consistently linked with depression.

The blue-green light will cause you to be night blind when looking into unilluminated areas. So if you turn off the main road to a road thats not illuminated as well you wont be able to see as much detail for 45 seconds to 5 minutes.

I was a helicopter pilot in the Army for 7 yrs and this scenario is well defined in our NVG training manuals and made to be a part of our annual recurring training. You can google the US Army NVG manuals, they are "google-able". The Army at fort Rucker also has this pretty cool room during instrument training, they make it completely dark and let your eyes get dark adapted. Then they show the pilots the effects of lights at different wavelengths and intensities and what it does to your night vision. Relaxing and fun! As far as aeromedical training the chemicals that kind of activate cones and rods during day or night are different. At night blue wave length light cause that chemical to be flushed out, and depending on the intensity -duration, determines how long it will take for those chemicals to come back and do their job - let us see in low light. I guess another reference would be the FM that covers Night Vision Goggles aviation and the aircrew training manual for the AH-64

Justin Douglas Evidence?

I think they should wait a few more years an install infrared LED's as those will be good for self driving car night vision :) Human's will be banned from driving soon anyway.

This might be a really dumb question but I don't know the answer so I'll ask it anyway. Why don' we use green lights to light up our roads? As I understand it green light requieres less power to create (why green lazers are so powerful while not costing a lot) and humans are really good at seeing green stuff (why we use green when filming in low light situations or using night vission goggles).


Don’t be absurd... there is a big difference between light production by LED and that of a laser.

Nice and rounded. Thank you! Also, kudos on covering light pollution.

Great article

i hear what you're saying about the SD lining up well only with the daytime response- but like you mention talking about "mesopic" vision: we don't immediately stop using our cones at night. They're always there and always 'turned on', they just have a lower ABSOLUTE response. Overlaying those two graphs that way makes it look like you're trying to say the sensitivity is the same but just at a different wavelength, when the absolute sensitivity is obviously lower. Based on that, I'm not sure that part of the video makes the argument that "SD lamps are bad because they don't align well with nightime vision"- they align reasonably well with the cones, so what's the problem? The better way would be to show those two graphs at the correct amplitude scale- then you could explain that SD lamps align well with the part of the eye that has a weak response, but completely waste the power of the lamp on part of the eye that is less sensitive than the part right next to it.

I don't really see an issue with the circadian rhythm disruption. In humans anyway. For one, the light output matches moonlight extremely well, and I don't really have any issues falling asleep in moonlight. (Also I have curtains.) I can understand If some are more sensitive but that brings me to the next point... There is no reason (except a little efficiency) a city can't employ two color temperatures, say 5700 for highways/commercial and 3500 for residential, where illumination is less critical. Combine it with the dimmable output capabilities and you are really onto something. Have the lights at full output from dusk til 11pm, %50 output from 11pm to 4am, and back to full output from 4am til dawn. As someone pointed out, I want to be awake when driving at night. And it's OK if my body starts putting me to sleep when I get into my residential zone, I'll be awake for the high speed portion of my commute and ready for bed when I get home.

Here is my biggest issue with the LED's, Rain, Fog, and Snow. Its like a big white wall were as HPS I could see through rain, fog and snow (respectfully). The LED's just make it damn near impossible to see through till you pass that lamp but the next lamp has the same issue and so on and so on. Thus why I like the HPS better. I wish the LED's were an amber color.

Not sure you mentioned - yes cyan light sources are bad, but on the plus side many accidents are caused by people falling asleep at the wheel. Blueish lights might actually help to counter tiredness in drivers.

I actually prefer cool lighting over warm any day! Never understood why people like "warm" lights...

I would love to see warm-white LED street light, haven't seen it on any road where I live. It should be better than cool-white, as it will be more pleasing to the eyes and less stress when driving, less road rage. lol

Anomonny SoundSys Nonsense

19:05 "I don't doubt that blue light can disrupt the circadian rhythm, that much seems certain. But considering that our eyes can withstand sunlight, which is far far greater than any artificial light (...)" That second sentence made absolutely no sense whatsoever. Not because the sun is not much stronger than any regular light (of course it is), but because it's a completely different argument that doesn't follow the previous one. People don't claim that blue light hurts the eyes (if they do, they're just retarded and should be ignored). What they do claim is that blue light disrupts sleep patterns (a.k.a the circadian rhythm of sleep). There are plenty of anecdotes of people switching their fluorescent lighting for warm-colored bulbs and curing their chronic insomnia, or even depression (which makes sense when you consider that some depression types are caused by improper sleep). I was really, really confused by that segue. It makes it seem, no, it pretty much proves that you have no idea what circadian rhythm even means.

Let me unpack that for you: 1. I didn't talk about how blue light is "ruining our eyes" because the science behind that is questionable. 2. _However,_ that's not to say it doesn't cause CR disruption. 3. But back on the blue light front, (etc). The order there wasn't great, but the point of reiterating blue light and melatonin was to hopefully avoid making it seem like I find blue light content irrelevant. I surely don't, but the fact that we can tolerate sunlight should prove that worrying about *eye damage* from blue light is silly.

Moonlight is an in outlier in that chart

But then you have to look at the other side of it - the sodium light is a very distinct light that gives you a basic light. But with white light then you make the deviating lights/colors stand out less in the night. Even more so when you have the light of the low pressure sodium lights. And for people with astigmatism the shorter wavelengths are a lot worse than the longer wavelengths that sodium lights offers. Blue lights is extremely annoying and I found the low pressure sodium lights that we recently lost here very comfortable.

LED also uses much less power than those high pressure sodium...and a higher temp light 5000K or higher (the whiter/bluer) makes seeing things easier even though it washes out some of the colors (less CRI) it makes much more sense to switch to these. Lower energy, and much more visibility

I am not a professional in the matter and therefore I ask why not using , as in modern car headlamps , asymmetric projectors / reflectors in conjunction with upsidedown lamps which send their light upwards in a special reflector adapted to the road width and the distance of the lamps among each other that the light / dark spots are prevented? Here in Germany I have seen many times modern parking garages they qork with LED side lights which are mounted near the ground and still illuminate everything without dazzling.

are airport runway lights blue because that is the easiest color for pilots to see at night or is it just an aesthetic choice?

I was super upset when they changed my street lights to LEDs. I still sigh when I see them at night.

Good video, although I have to disagree, the bluer light also help minimize SADD (winter blues so to speak) I have replaced all my indoor lighting with cool white LEDs and its so much better.

They might have never seen the milky way, but did they never see images of it?

We remodeled a ton of old fixtures, removing the ballast and installing a LED system instead. I wouldn't want to use the old ballast with new light sources.

Light pollution can be mostly mitigated by better fixtures and blacker roads (blacker roads make daytime driving safer, too, since they make the sun less blinding), and messing with the circadian rhythms of drivers is *good* -- we don't want people falling asleep at the wheel, and falling asleep at the wheel is something that's much more common at night. Plus, in terms of tradeoffs, less human road deaths is better than aesthetics or circadian rhythms (which are already messed up by skyglow, anyway).

New LED design uses violet LED chip to excite phosphors, eliminating blue peak, and very natural, sunlike output:

the fuck are you talking about? less drivers on the road and it's easier to notice what's going on around you without ambient light. i prefer night driving unless i have shit headlights.

I would like to see a switch to street lighting with sharp spectral lines, so you can put a filter on your telescope for astronomy :P

Before high pressure sodium most streets were lit with fluorescent, mercury lamps, and incandescent lights right? I haven't been able to find much literature/media on this topic.

Bouncy, Bounce :)

I grow shitloads of high grade cabbage on LEDs, and my electricity bill is about the same as the neighborhoods.

I like lights with cooler tone than warmer tone.

Wrong! High pressure sodium and metal halide lights are far superior to LEDs with regards to night time safety. We do not see blue better than yellow or white light. LEDs are washed out even if they have high luminosity. Blue is a shorter wavelength and is absorbed by surrounding much quicker than longer-wavelength orange red yellow or white light

Its groton not growton lol use to live there

I have subbed...

I dislike the new LED lighting for a number of reasons, mainly being that as they are very directional, it creates a bright flashing effect at the top of my windscreen as I drive under them which is very disrupting and annoying. There’s no doubt that blue light disrupts circadian rhythm, that’s why in my place I use the Ikea lamps that you can dim and change the temperature of so I can use daylight in the day if I need more light and warm white at night. I find my eyes very strained and fatigued after a long drive at night with the cool white LEDs, especially compared to the same usual route I drive to the coast when it had HPS and LPS street lighting. Maybe it is the flashing effect that causes the strain in my eyes though as I don’t feel that after just walking around at night outside under those lights.

nup dont like non yellow street lighting, it looks aids. enuff said. fuk science.

Oh nooo we cannot see the night sky anymore. What shall we do.... Maybe switch back to unsaver road light so we can finally see the night sky.

@8:07 Light pollution is also disruptive to animals. You touched on it a little bit later in the video with the sea turtles. It also affects insects in general and migratory birds and monarch butterflies (I think the only migrating insect).

blue light is an excellent idea for motorway driving then. less sleeping at the wheel!

This has nothing to do with what I studied nor what I do for work, nor I have any previous knowledge on the topic. However, I just watched a 20 min video on public lighting, and enjoyed it...

That doesn't matter much, since the two (transformer and LED) come together and are not separately sold. I've actually verified that what's usually failing is the transformer, not the diodes themselves. I don't see how this would make any difference, since the hour ratings are OBVIOUSLY inclusive of the driver and fixing them is not an economically viable option. I would have to find a suitable transformer, buy a bulk of the things, then unglue open every bulb that fails and figure out a way to swap the transformers, fit it all back in and glue back the assembly. I doubt I could find a cheap enough transformer (unless I wanna buy a container full of them to lower the unitary price, but then... Nope, they just suck.

Federico Spadone There is a difference between power supply (driver) life and LED life. You need to learn there is a difference and the hour ratings aren’t mutually inclusive and don’t include average power supply life. Figure it out!

praestant8 such a poor trolling attempt bro I’ve seen much better.

589nm Maybe you need to see an optometrist for your issues instead of complaining about lighting.

praestant8 how much research have you done?

Brian Su Don’t be absurd.

My good sir you just earned a new sub for that explanation at the end

The use of LED's in residential areas is very problematic. A large part of the problem as pointed out in the video are the drop in LED replacement lights for older poles in residential areas. The spacing of the poles was implemented with the lighting characteristics of sodium lights in mind. When municipalities just drop in new LED replacements they don't take the number of lights or the spacing of the lights into account. With the number of lights and the strength of LEDs, any possible illusion of night time is ruined. Every nook,corner, and cranny is flooded with light. I personally find this very grating living in a neighborhood that has replaced all the sodium lights with LEDs because the night almost doesn't exists anymore, it just feels like a dimmer time of the day. I can walk out into my backyard and see just about everything pretty clearly and that doesn't sit right with me.

You actually want the circadian rhythm disrupted in this case. Cuz your driving and blue light will help keep you awake, alert and a lot safer while driving. So you could say instead of the blue light disrupting circadian rhythm , blue LED lights are better for visibility and help keep the drivers awake and alert.

When my pupils are dilated (because that's kind of the definition of night time), LED's hurt, which means I squint and periodically close my eyes. I don't know about you, but I'm scared for my life every time I have to close my eyes just because the oncoming car uses LED's instead of halogen lights. Ban LED's from headlight usage.

Uxwbill's brother by another mother

Very thorough, well presented, and relatively unbiased video. Thank you.

i think disruptung circadian rhythm is probably a good thing for drivers. you dont really want drivers to be lulled to sleep while they are driving.

so if blue lights are better for night, why are so many emergency lights red?

What a gem. Excellent disambiguation and clarification of so many facts in the one video. Well done!

I agree with illiteratebeef that circadian rhythm disruption is actually a good thing, at least on freeways without a lot of sleeping humans and animals around. Of course, I don't really have much of a normal circadian rhythm to speak of anyways, so it doesn't bother me none. I actually have a "daylight" LED bulb on in a lamp in my room 24/7. I can't sleep in the first place without medicine, and I always feel more comfortable in the light. I actually strongly disagree about the aesthetics of cool light. Yellow lighting seems sickly to me and any amount of detectable yellow in the ambient lighting rubs me the wrong way. I prefer truly "white" light that casts neither a blue nor yellow glow, but blue is far preferable to yellow.

came to find out why HPS is being phased out,also got a 10 year lesson on how our bodies react to the lights which explained why there being phased out. this is how a channel should be run.videos like this. its not a 100% explanation is a 1 billion% explanation. beautiful.cant wait for the next vid.

Awesome video! Great info for voters and communities. Congratulations!

I wonder if peoples' stress, depression, anxiety, or overall mental stability are significantly impacted by different light sources. Does LED vs High Pressure Sodium influence people's mood besides their sleep pattern (circadian rhythm)?

The "blue light is ruining your eyes" thing was something I was taught in college. I don't have any studies to back it up, but the teacher explained it in that blue light is just on the edge of our vision capabilities allow towards the UV range. She displayed other colors that appeared crisp and clear and then she used the blue color similar to what we use in traditional hypertext links and the blue color produced a double vision and blur effect. She proceeded to explain that while it is mostly visible, our brains/eyes have trouble focusing the light so our brains continually try to force our eyes into focusing on it and our eyes are incapable of focusing on it. Over long term exposure, this can not only cause strain on the eyes, but it also the brain also starts trying to interpret the light in different ways similar to how if you wear a lens that flips your vision upside down for about a week your brain will flip the image right side up and then when you take those lenses off you'll see upside down for about a week if I remember right. I think it really comes down to what specific spectrum is used, because blue is so close to the ultra violet spectrum, some shades are more problematic than others.

"our eyes can withstand sunlight" Speak for yourself, I need sunglasses even on most cloudy days. Good video though.

Light pollution is not only a weird problem for astronomy, it's a deathtrap for most nocturnal insects. The bluer the light, the more insects get attracted and likely die. Some insects like most fireflies are already almost exterminated due to human light pollution. Light from low-pressure sodium lamps (590 nm) are still one of the best choices in respect to environmental protection. The only lamps that are even better, are warm-white LED with light below 3000 Kelvin. A good LED has a yield of approx. 300 lm/W, a low pressure sodium based lamp up to 200 lm/W. So yes, there is room for LED lightning to save energy, but the LED lamps should have an even better protection for insects i.e. produce light that is even more(!) into the red spectrum. And please.. "elemental sodium" is.. dangerous? Get yourself a basic book about basic chemistry and toxicology.

I live in an observatory town (apparently the largest telescope open to the public) and the city has been replacing all of the street lights and fixtures to LED flat fixtures you mentioned and the light appears much brighter and appears to be more of a white light color range than a blue light.

Blue light only disrupts your circadian rhythm when you see it at night; if you see blue light during the day, it reinforces your circadian rhythm (which is a good thing). It's an amazingly beneficial coincidence that the sun, whose light includes a good amount of blue in it, shines during the day instead of at night!

*Until we've completely adopted driverless vehicles, aren't lights that keep you awake at night a good thing? (nvm this was already addressed in the comments).*

Am I the only one who doesn't like warn color when watching TV, monitors and such?

Can we stop beating it off to "lower energy consumption" of LEDs? When do you mostly turn light on? At night. When is the time of electricity production surplus? At night. So there is no actual resource saving by consuming less at night. The electricity gets still made.

My main complaint with the new LED lights is during the rain at night. (Which is pretty common for me, living in Seattle) Especially the ones that aren't diffused at all, acting more like focused spotlights. The raindrops on the windshield create a myriad of little lenses that redirect the lights directly into your eyes, like having a bunch of little LEDs placed against your windshield blocking your vision of the road past the raindrops. Windshield Wipers help a little, but the raindrops are continuous and immediately begin refilling the windshield as soon as the wipers pass.

Wouldn't higher melanopic light levels also feed into road safety, as it should lead to lower levels of drowsiness in drivers at night?

I am amazed that anyone could spend this much time and "worry" on street lights and still be "solution-less" or come to the same conclusion of current practice (sodium vapor lights)!

Blue light definitely is harmful to the eyes, but taking that into consideration when talking about streetlights is just silly. As you pointed out, sunlight contains way more blue light than the most powerful cool-white streetlights and even that is not too harmful. But it really is something you have to think about when you work with powerful light sources and lasers ;) There was some legitimate research into this and you can find some of it, just search for blue light hazard.

Then why in the world Cooler temp Headlight bulbs are illegal in many areas?

The last few years I've been seeing led lights popping up on bike paths that output green light. What's up with that?

I personally find 2000-3000K light temperature bulbs to be incredibly displeasing, as if everything has been covered in vomit... I could probably somewhat contentedly live with 4000K however. Anyway, personal preferences aside, good video.

I always liked the color of Mercury Vapor lamps, wasn't impressed when they slid high pressure.sodium bulbs in their place.

I always use UL type B ballast bypass LED drop in lamps

Meralco, the electricity provider in Manila (capital of the Philippines), Bulacan, Cavite, Rizal, and parts of Laguna and Batangas used Mecury vapor lamps in streerlamps until the late 90s when they replaced them with high pressure sodium. Starting in the 2010s, they started to use LED lamps for installing new or replacing broken HPS streetlamp systems. Still working HPS lamps are still not replaced.

Get this light out of my sky!

I do not like how blue light makes you squint. I hate oncoming traffic that uses blue lights and I would also hate it is street lamps used it. It is just unpleasant to look at not aesthetically but because of the physical response of squinting that it causes.

People may prefer the light from a blue lamp, but I'm not sure that actually means they see better. I think it feels brighter to them, but all blue light is doing is making them squint, which they interpret as being brighter. It's a scam.

In the UK one of the motivations for replacing sodium with LED's is so that they can just turn them off remotely since the old ones don't have that functionality in order to save money they've moved to only turning lights on near junctions and roundabouts and off everywhere else (at least in the North) which is really dangerous

Aesthetics? Cold light looks way better in night and in general. Marketing knows that, thats why smartphones come preseted to cold temperature color like the galaxy s. I believe you have the wrong idea. Most ppl will prefer blue light, its you that dont. Btw very nice video, thank you so much for the effort to make.

The cold color temperatures remind me of some dystopian future.

I think using the cooler LED lights would be good on major highways and roadways and the warmer LED lights near residential areas. Circadian rhythm disruption might be a positive thing in that case keeping people awake on major roadways where they drive faster. Personally I like daylight bulbs because its easier to see and colors look more true.

Kyou Nagato Boo hoo. Suck it up

they won't. If you are tired you need to pull over and find a hotel or just sleep in your car somewhere safely. Preferably NOT on the shoulder of the highway. I mean, there is a reason they say don't drink coffee to stay up 48 hours to do more work. 1, it's not healthy and it hurts your organs and your brain, and 2) your productivity goes in the toilet once your body senses it is overdue for sleep, regardless of how much coffee you have ingested. You cannot change this, it is your nature. We evolved the mechanism of sleep, not because we were primitive, but because it is more efficient than having to stay up 24/7. We can spend 8-10 hours a night NOT using a ton of our energy reserves and eating more food. And it is also less stressful on your body, allowing longer lifespans! Attempting to interrupt our circadian rhythms will result in lowered levels of productivity, concentration and health.

Here is another idea related to safety, taking the near-to-medium term future into account! Let self driving cars slowly take over in the next 10-20 years. They can rely on their LIDAR installation to navigate (even if there may be pitch black all around in the human-visible spectrum). Doing all this with much more safety than human drivers can. And then we can use lights at night with low color temperatures that don't disrupt humans' circadian rhythms.

Most of the lights here have been swapped out for LEDs here, sky glow is massively reduced and the light down the road no longer shines into my bedroom window. Pretty stellar when installed properly!

I'd like to see a video about the dangers of ultra bright lighting on cars themselves, too bright to be anymore useful than stock, and can actually blind oncoming traffic. What's the perfect wavelength for an efficient headlight, that's not going to blind oncoming traffic, especially at lowbeam setting?

Several things you don't mention: the "blue" problem with the LEDs is even when they are low color temperature, a grotesque "blue spike" at 450nM is still there, just lower intensity, with little light in the 480nM band (where the eye really sees well), and a broad hump centered at 580nM. What is needed is a true "thermal source" with proper spectrum throughout. Amber LEDs: these LEDs are the least efficient of all colors, and are most sensitive to heat (of all the colors), losing efficiency rapidly as they warm up. With the advent of multi-chip LEDs, lamps need to be made that have different color LEDs combined to give proper spectrum and eliminate spectral "holes". You casually mention assumption of 100% power supply reliability. Bull! 99% of streetlights will go to the junk because the power supply fails (and the repairman can't just "screw in a new bulb"), or because they will be superseded by newer technology in 5 years, and are thrown away perfectly working. Another thing that does in LEDs is corrosion. Even though chemistry indicates copper leads should resist corrosion better then nickel-steel, the steel seems to defy logic and last longer. Copper in ballast transformers and oil AC caps age much better than spread out on circuit boards, along with electrolytic caps which have no place in a streetlight. You can clearly see this in lead corrosion in LED (high) and incandescent (low) Christmas lights. Regarding "screw-in" lamps, these are better to deal with advances in technology. Socket in my porch light fixture (for weird CFL bulb that keeps burning out and can't get any more), I replaced with good old Edison socket. I can now put in Phillips "flat bulb", my choice of warm/cool white. Another thing about sodium light to consider: you know about EnChroma "colorblind glasses"? They make a version to use at night. This has 2 spectral notches, one at ~585 +/- 30nM, and the other at 485 +/- 20nM. Yellow notch reduces effectiveness of sodium light as it falls in the notch. In the future, 8% of males could be wearing these, and driving at night.

The best light to SEE things instead of being blinded by glare, has the least blue spectrum in it. When you started making claims about efficiency at 15:40, you were using a very bad example, one where they were only 67 lumens/W? Really? Warm LEDs now achieve over twice that, a mere one example of a device that doesn't is not a proof of technology, only that a particular product should be avoided. You are welcome to consult the LED datasheets from major brands like Cree to see that what I wrote is true, that warm tint LEDs are not remotely that inefficient today. More importantly, if you subtract the glaring blue content of the light, they are MORE efficient at producing color spectrum that is usable to see well. Did you GET that? A lower lumen warmer light has more human-usable light. A higher lumen bluer tinted light has more blinding, detrimental light. The extra lumens are the worst possible thing.

Man, you prefer those depressing ass orange lights at night? I can't think of anything that makes me feel more lonely and wishing it was day. I hate the orange lights with a passion and have since I was a kid.

Arguably, any billboard is light pollution.

I like the video. Solutions: 1. Turn off street lights at 2:00 am. No pedestrians. 2. Close your eyes at night. It's bedtime. 3. Switch to LEDs and destroy all sodium vapor lights. I prefer mercury vapor as long as it's not 20 year old green.


Combine both, use HPS surrounded by some LED spot bulbs thats all, you can lower the wattage of the HPS and use some 6k LEDs

Hang on. The cones sill respond to the light (it's normal photopic vision). You are creating a false premise here. The problem with sodium vapour lamps is NOT the frequency, it's the bandwidth. Very narrow. NOTE to you: When you are dark adapted, this DOES NOT DISABLE THE CONES! In fact they are even more sensitive as they are no longer being bleached by the photopic light levels. What is happening is the cones are now becoming more sensitive as they are normally bleached by photopic light levels.

Circadian rhythms is complete bullshit. It's one of those fancy pants words that nobody heard of a few years ago and now suddenly everybody is sleep deprived. Just switch of the lights when you go to bed.

Then why do yellow glasses, which I use when night driving, reduce glare from LED and HID headlights? Also remember that France did scientific tests years ago, and mandated that their headlights be yellow, not white.

Great video, really well researched

A pupil of a human eye reacts the most to blue or green light, and red light has virtually no effect to pupil shrinking. If the effect of the light wavelength to the pupil changing size is also taken into consideration, orange is actually the best lighting color for seeing in dark, because it does not affect pupil size very much but human eyes still have much better response to it compared to red light. Higher color temperatures, than orange light has, actually have so much effect to pupil size, that it makes it very different to see anything that is outside the area where the light is mostly focused on.

@6:13 - Correct me if i'm wrong, but having melanopic content increase with scotopic content is not a bad thing. We don't want drivers falling asleep at the wheel. It's ok to have their circadian rhythm messed with if they are behind the wheel as safety >> sleeping.

I thoroughly enjoyed this video, never wanted it to end! Subscribed!

Would the melanopic light and it's associated disruption of the sleep cycle ultimately have an unexpected POSITIVE effect in reducing drivers falling asleep behind the wheel?

Great video as always! If anyone wants to learn more about the spectroscopy of Sodium, I found this PDF to be interesting:

Personally, I much prefer the LED street lights. And I agree that the cobra-head street lights are terrible and need to go (despite wanting one of them along with an admiral hat lamp for my collection) I almost don't need lights on in the front of my house because of the street light across the street. As for the blue light emitted by LEDs, commonly found in the new street lights as well as electronic devices, major manufacturers like Apple and Samsung are adding functionality into their devices to reduce the blue light emitted. If they're doing that, I'd guess that this is a relatively known issue. With that said, here are a couple of more credible sources of studies on white light... Harvard Health Publishing National Sleep Foundation WebMD

I personally love the color of sodium lighting but I can see the road benefits. Though maybe residential areas should still use sodium lighting as while you want people awake on highways and main roads but in residential areas you would want to promote sleep while still providing lights. That's my perfect world situation

Anecdotally, there is some aspect of adaptability re how much high color temperatures actually interfere with circadian rhythms. Around 12 years ago I switched the lighting in my home to be all 5500-6500K, at the time using specialty high-CRI fluorescent tubes and CFLs. This messed with my sleep schedule for a while, but I eventually got used to going from bright daylight-equivalent light exposure to being asleep in a matter of just a few minutes after turning them off.

On a recent 4AM drive to the airport I noticed that all the highway lighting along the way had been replaced with LED. Everything was much easier to see. They were also very well aligned so that the road, and about 20 feet on either side, was highly illuminated. Everything outside of this received very little light at all. I don't know what color temperature they used, but I would guess it is in the range of 4500k. It was 'whiter' than the 4000k LED tubes in my kitchen but not as harsh as a 5000k 'daylight' LED bulb.

I was about to make a comment about how street lights making me less sleepy would probably be a good thing, but I see that it's already pinned! Also worth considering is that in South Korea they've installed blue street lighting to help combat suicide, as they've found that blue lighting makes people think more positively.

I generally prefer warmer light colours, however sodium lamps are perfectly placed on the spectrum to cause me migraines. it's physically painful for me to look at sodium lamps, boy optics lessons were "fun".

can Sodium lights be adapted to have also other gasses to change the bandwidth of light emision?

And there are people who claim that blue light is bad for your eyes.. ( and more ?) which is interesting to research on.. ( answered in video )

Thank you for mentioning circadian rhythm around 5:40 ! I was afraid you might gloss over that effect, and very glad that you seem not to! Continuing watching now.

Excellent video, I learned many thing, but I have one point of confusion: at different times you spoke of “cooler” color temperature (more blue, yes?) and at other times “higher” color temperature, again I think meaning more blue frequencies. Looking at charts I see 6500° as more blue and 4300° as more red, but the blue is called “cool”? This is very confusing to me, because isn’t 6500° over two thousand degrees *warmer* than 4300°?

Good old sky glow. I live in a rural area with a giant chemical plant (let's just say that last time it was on fire the flames could be seen from over a dozen kilometres, to give you a size idea). Above the towns there's small glows in the clouds. Above the plant the sky is illuminated for a giant stretch. In fact, when I'm in bed with the blinds open (~5km away and facing 90° to the plant) a full moon night is darker than a cloudy one.

The ballast in any of the light systems used has no effect when using an led replacement since they are just for current limiting but the igniters have to be removed the the high voltage they can output will fry the led

I'm fairly sure there is no official investigation into this. I hate LED lights in general as they flicker and give me eye strain. I suspect there are actually a noticeable amount of people with similar issues. This actually INCREASES the chance of accidents. I would like to know if any investigations have actually been done about this.

cold colors are not what humans have adapted to. All humans like warmth because it reminds us of the sun, which we depend on to survive, of course. No one likes to be cold.

True, although organic parts have much more variability. The proportions of blue to green to red cones also varies a lot. I've even heard of some gene that makes red cones have a slightly higher peak wavelength than normal (basically a mild 'anti' color blindness), which widens the gap between green and red cones by about 10nm.

indeed,although that said, even manufactured parts have error margins and fault tolerances that can be quite significant, for instance computer CPUs that go through a binning process to sift them out afterwards, the margins can run into double digit pecentages on the more problematic process nodes. but yeah, trying to quantify the spectrum sensititivty falloff of the human eye into a score sounds pretty complicated. i sure do like the options of narrow-band light led provides, and the abundance of color temperature options TL had.

Photons are funny. I've heard and seen several different ranges for the visible spectrum in different science books and material. Sometimes they say 400-700nm, sometimes its 390-730nm, sometimes it 400-750nm, or even 390-770nm. Eyes aren't some manufactured part, so there's more degree of variability. Well, I have some 3W 730nm LEDs (called far-red), and everyone I've shown them to has said they are visible, but they give very different answers on brightness (ranging from 'can read a book', to 'uselessly dim'). The CIE will say that "anything over 700nm is infrared", but it's not that cut and dry.

well the sodium light sure travels further, and seeing as they're mounted up pretty high, and the individual led modules aren't of a high wattage (inverse sqare law) i totally agree with the led streetlights being dimmer at ground level, but i'd argue it to be a power/intensity problem rather than a color temperature for those, they should be using at least 10 watt modules in an array to get a proper stretch for say 6 meters, but i think they generally use less powerful ones. but for my everyday house application where distance isn't really a problem, i like the cool colors of leds, but i would even agree cooler light is a bit more fatiguing to look at, albeit in a different way i still i prefer it. led arrays can also get a pretty good sqare suface lit evenly, without too much dark corners that are a natural effect coming with big, single source lights that emit in a spherical fashion. also, cloudy days in the summer can actually be the worse to me, when you have this awful greyish white but very bright emissve background on everything, that's actually worse for my eyes than a clear blue sky (or technically what our eyes interpret as blue)

The warmer color lights seem to give more light for me, and to my eyes the old sodium vapor street lights look brighter than their LED replacements. I also need sunglasses to go outside, even on most cloudy days, so maybe my eyes are weird.

i actually prefer cool white bulbs in my house over warm white anyday, i also feel they give me alot more visible light for the same wattage, or at least, light that's actually useful to me, i find a lot of tv's are usually way too redish for my taste when they come out of the store too. i know anecdotal, and subjective... but that's how i see it. (literally lol)

I was about to type this and was like, way I’m sure someone else has already and bang there it is top of the comments.

I'd prefer very white to blue .lights comapred to the orange.

I think having the cooler lighting (blue) light at night would be a great idea. This is my assumption, but if the blue light disrupts sleep cycles and is more likely to keep someone awake ... Would that be a bad thing? I think it might actually help with drivers stay awake and more attentive to driving. It could help a decent amount with drivers falling asleep at the wheel. I think the best way this could be done is have blue lights on the highways and dangerous roads that people are more likely to fall asleep on, and more calm and yellow based light in slower traffic or in neighborhoods.

I've always found that it was easier to distinguish things from each other under sodium lights, while LEDs mess with my ability to focus. when they switched to hps I was super grateful that my eyes weren't being fucked with anymore.

Something I have noticed here in Australia with newer HPS lamps is that they are horrible in fog. Along some of our rurel highways and freeways they are mounted around intersections, and if it is foggy, you can't see into the fog until you are directly under the lamps.

I thought LED, sodium, etc...had already been replaced by LCD technology - I see drivers being "illuminated" by their cellphone screens more than other light source on the road day or night. Doesn't seem to offer any bonus to safety unfortunately.

Why 3000K LED? That seems excessively yellow for aesthetics _and_ every other factor for that matter... Unless you can go all the way down into the orange, IMO you might as well stay white to whitish-yellow, not some weird yellow glare. Sounds like it would be more efficient and improve reaction time too, so...

These are the issues dividing this nation

Vouch on the circadian rhythm being disturbed. Not me personally, I am essentially nocturnal, however everyone with a road facing window on my street has new issues of sleeping when the new lighting was installed on our road, it went from sodium lighting to something white, I can't say what, I doubt it's LED's, it looks more like halide due to its change in colour after ~30 seconds of warming up. Croydon, London if anyone wanted to do more research into it. *rant* I much preferred the sodium lighting on our road, a small cul de sac with little to no night life apart from animals. Fair enough on the busier roads. However not only were the new lights brighter and whiter, they were placed every 10-15 meters, compared to the older ones which were more sparse at ~25m. Not to mention the old lamp posts were gorgeous, green and had some beautiful patterns on, only really needed some paint. It's a shame I can't find any photos of them. I go out when there's a power cut at 4am now, to see how beautiful the place is at night without the gross light. I'm not alone with my dismay, it caused controversy throughout several parts of Croydon.

Interesting video same thing is happening with horticulture. More people are going from using hps and metal halide to led and it's happening quickly especially with Cree and Vero making such good cobs. Thanks for this video super interesting.

If only they would actually install decent led lighting instead of the cheap crap they put up on my road. They no longer illuminate the road/pavement but everyone's bedrooms are like daylight!!

There is an important factor that needs to be compensated for in your normalised efficiency chart, that is blue light causes the pupils in our eyes to contract and therefore receive less light.

Nighttime lighting should never exceed a colour temperature of 3500k because having daytime colour temperature lights at night simply messes up the body's inner clock and gives you lots of health problems. Not being able to find some sleep is just one of the side effects. Long term effects are even worse. Your eyes also need a rest from all the blue light.

flickering / strobing LED will be "awesome" :-/

They need to make sure that the light pollution does not interfere with Astronomy light pollution rejection filters. Also since LEDs do not require a ballast to turn on I think that they should use motion sensors with timers so that they are not on when no one is around

What if you get electrocuted by the LED?

I myself think the yellowish color of sodium lamps are horribly ugly

can confirm. A main road near where i live has now retrofitted LED streetlights with warm-white LEDs. They are slightly but noticeably brighter than the regular sodium lights but not too harsh and don't hurt the eyes too much. Overall they do feel perfect for that purpose. So far the best use of LEDs in streetlights i have seen so far.

I actually don't care too much if you're throwing cold or warm light my way as long as it isn't that bizarre dry yellow.

It depends what your idea of 'cold' is. I'm perfectly comfortable at 55F, but 70 is too hot for me to be comfortable inside a building. I don't like cold color temperatures, as I've stated before. The whole 'color temperature" system doesn't make sense either, after all it was made by the same people who say "anything over 700nm is infrared", which I know to be pure crap, because I have some 730nm LEDs and they are visible.

That's mostly the point, wanting to go cheap. Even 3000k is too white, I settled for 2700K filament led for home, pretty close to incandescent. For street 2200K should be used.

Those people living near can be affected and actually increase their chance of being involved on an accident in plain daylight from a bad quality of sleep. Don't patch a problem that may make the problem even worse.

What's more important, people or cars?

It's the cool tone the root of problem, sodium orange tone makes it pleasant as a street light.

Sodium lights makes sleeping near one a non-issue, years ago we had cool tone CCFL, was a pain the ass.

Couldn t you just put a blueish transparent glass under those sodium lamps to get that color? Or just put a blueish sticker that does the same?

Those fucking lights are blinding to the car infront. When i get one on my ass they hit my mirrors and nearly blind me like high beams. High beams have restrictions for a reason.

Blueish tones are annoying, specially at night and distort your internal clock. Even worse at a neighborhood with a 5000K+ plastering the streets, there a reason why communities in europe change their early cool LED's for a warmer tone like 2200K.

Here in New Zealand they aren't mucking around. HPS fixtures are being swapped out for LEDs at a great pace. Our entire town has been done, as have all others in our region. There are very few fixtures that still remain as HPS but I think these are the ones that aren't administered by the district councils. The ones they have installed here are on the cool side of warm. And the place does seem darker than when the HPS ones were there. Perhaps they cut down the lumens as well to increase their energy savings even more? I'm glad you called out the BS of the whole blue light from LEDs damaging our eyes. It does seem pretty silly. I wouldn't want to have to go back to incandescent lighting as it would be very difficult in our off-grid situation to manage the energy requirements!

As a person living in CT (where the light study was done) i cringed at the pronunciation of Groton. You say it like brought; g-rought-on Other than that cool video

Maybe 4000k LED is warm enough. And make it bright as hell

Illuminati confirmed

This is fabulous. I watched the whole thing, I love leds

LED streetlamps are great for all the reasons you mention in the video. However there are two drawbacks that I've noticed since they were installed locally. 1) The colour of the LED lamps are too similar to car headlights, this means that you can't immediately tell if light coming around a corner is from a car coming towards you or from a streetlamp. It becomes obvious within a second but it's still enough to cause confusion and hesitation. 2) The old sodium lamps gave good coverage between lampposts, the LED fixtures they replaced them with don't cast enough light sideways so we have lots of dark spots which are a safety hazard, not just for traffic but for lone pedestrians at night. A well designed replacement fixture would easily give enough sideways coverage so it's not a problem with LEDs themselves.

Also I believe the problem of seeing problems on the road should be solved by putting low output high temperature lighting on vehicles instead.

About time somebody talked about all of this

You need to emulate the spectral response curve of sodium lamps but improve on it by adding limited blue frequencies

Blue light is disturbing at night. If we switch to LEDs at high color temperatures, we are condemning our society to even worse sleep disorders.

I think Higher CRI LEDs like the Nichia 219c would have all the benefits of LEDs and they would look aesethically pleasing as well.

I learned a lot. Thank you.

You need to lose wight.

This is one of the best best videos I've seen on street lighting.

Being in Disney World, it appears they are not switching over to LED.

Studies show something like a 30% reduction in crashes and fatalities when comparing an unlit to a lit roadway.

I hate hard white LEDs. But would be fine with the warmer LEDs.

I remember reading an article in what I believe was Popular Science that was by astronomers against LED lighting. They were near a city they had recently passed a resolution to remove sodium lighting in favor of LEDs. I believe they said all sodium light can be filtered out because it doesn't line up with anything significant in the night sky.

Star gazers hate sky glow.

i say we should go back to carbon-arc lighting. high amp high voltage electricity and boogoodles of UV be damned.

Filament led offers a greater efficiency, my Phillips 2700K filament leds have an efficiency of 135lumens/watt 6w 804lumens Dubai Led filament already reached 200Lm/w

Rainer Riegler You need good ones though. I made mine with an extra thick layer of dark fabric sandwiched inbetween a thick fabric I used for the outside, from ceiling to just touching the ground. If I close them, it might as well be nighttime inside. But even with these expensive as shit curtains, still light will peek through.

I've never really experienced HPS Lamps in my life. Onlyfor a short while, when I was in Hamburg in certain areas. besides that, the Standard here were normal Flurescense lighting.

Blue LED's are horrible, no amount of safety or economic arguments should win for this reason.

Excellent video as ever . I think I understood most of it. I certainly got that this is really important. Perhaps a summary video for those like me who need appreciate the conclusions. Facts rock still :-)

Fascinating! I had a couple of questions for the guys who redid the lights in the neighborhood. All they knew was the CT. The conversion was very strange, they started with the intersections, so a bright orange street would give way to a relatively dark crossing. When the planet switched to CFL's, LED lighting tech was already on the horizon. Is there something in the works that is even more efficient than present LED's?

Just found your channel. Oh man, I love it. Your work is fantastic, but your presentation... I can be fascinated by you reading a manual.

In Amsterdam there are a lot of decorative streetlightpost and a few years ago in some streets they changed them for decorative LED streetlightposts. I was horrified by the effect, not only is it a very harsh and cold light but they also blind you a lot more and thus actually make visiblility less. At least I noticed this riding my bike. I do not drive my car here so I can't compare with that. When I drive my car on for example an highway with bright LED lighting, yes visiblity gets better but also in some cases it can be a bit blinding. Especially when you enter a less lighted area. I'm no big fan of bright streetlights and sometimes even annoyed by them. I don't even want to talk about oncoming cars with bad modern lighting.

You definitely made this topic interesting and engaging. Thanks for in depth presentation. Very informative.

I was thinking this too. Maybe have cooler temperatures out on highways and long roads away from housing and warmer in suburban areas.

Cannabis Farmers are already switching to solid state lighting

This is informative while at the same time BORING! Yet I agree that LED lighting should replace ALL public light posts and lamps, etc.! Also, I FUCKING HATE THAT YELLOW/AMBER LIGHT!

This is a difficult problem with no 100% correct answer. You have to weigh the pros and cons quite a bit and I'd bet the best answer varies from area to area, ven within the same city. It's a very interesting topic too. This video was definitely worth while watching.

My town already switched to all LED street lights.

How did this video got in my recommend I never watch any of he video and I do not know WTH he talking about but it look good I think I did learn something new

4000K LEDs are the best compromise!

My main gripe about street lighting - at least since they abandoned incandescents - has been the limited color range, particularly in the case of sodium vapor lighting, which is the most limited of all. As a photographer, this is death to a good color image - you cannot pull "good" color out of a photo taken under sodium vapor lighting, since it was never there in the first place. You're basically taking a monochrome shot.

The anecdotal story about Los Angeles residents being "frightened" of the Milky Way is a little silly. On any clear night - particularly during the dry Santa Ana winds - you can walk out on the beach and see it. You don't have to go miles away from the city, and you don't need a power blackout.

Have you done a similar video on automotive headlights yet?  That's another related issue with a number of important elements: cost, long life, driver's vision, and oncoming driver glare.  Seems to deserve its own treatment.

Haven't seen a HPS for so many years. Didn't think anywhere still used them.

I think when you are on road driving a car, skyglow Will be the Last thing you would Care about

There's no such thing as circadian rhythm. Your brain can be trained to follow any sleep pattern, regardless of what light you're looking at, your brain can be trained to sleep when it see's it. Light alone makes it hard to sleep, so at this rate you might as well not have any lights. Changing the light color is only an excuse to botch something that works as it should. If you have trouble sleeping you cover your window or you put something over your eyes, you don't use poor lighting, especially on places like your phone. People use poor lighting on there phones because they want to blame the phone for them not sleeping, while in reality they should be blaming them selves for looking at the phone in the first place.

I remember my street having a blue/white lamp about 25 years ago, before that section was standarized with sodium lamps, shortly after. I've been walking that street under yellow light for most of my life, so I got used to it (as I have to pretty much the rest of the whole city, it looks just the same) that, until my dad just recently added a LED light to our back yard, for late night/early morning lighting. I can't see shit under that light.... it lights the area just fine right under it, but it fades out too quickly over distance, and I'm talking about a square garden barely 10 meters on each side. the city hall also uses those lights around the city center for public spaces, and I can't see shit there either. the very little I recall about those old white street lamps, is that they felt pretty much like that LED garden lamp. I feel more comfortable in complete darkness lit by moonlight, that under those LED lamps. I also switched the bathroom lights from 30w incandescent to 9w LED, and they shine right in my face,... it's not the warm soft light I'm used to... they feel completely off. they're great for night lamps or desk lamps, but, lighting farther and stronger? no thanks, give me a sodium lamp any day.

Its not a choise of aesthetics. You might dislike white LED light, i don't. I loathe the candle-like lighting of sodium lamps. The whole of Asia perfers >4000K as well. So if the safelty, energy efficiency and longlivety is better with LEDs, its pretty much a no brainer. Only a couple of elderly displeased with white light is a rather low price to pay.

I live in a neighborhood where they switched to LEDs and I could see the stars after and could not before. I think they are far better. Better visibility and people will be less likely to fall asleep while driving.

scared of milky way.

Maybe it's time that we evolved from using glorified torches

I live in a small town in rural NW Missouri, and in the past few years I went from fighting against light trespass upon my countryside property to being a fierce Dark Sky advocate. The entire region, from small towns to isolated rural homes, has embraced unshielded LED street lights, barnyard lights, and "insecurity" lights from dusk to dawn. Building and residential lights are mounted to shine out horizontally causing glare and light trespass literally for miles, not to mention sky glow. Regarding a light ordinance, I'm up against as close minded and vindictive a small town mentality that it could feature in an anti rural Hollywood movie. I've created this facebook group, which not only has countless article but chronicles local light pollution and my struggle against it.

led lights just blind you!

the only reason why it is higher at night is because perdestion is stupid running around in street aka Darwin award

I really like the look of the sodium lights.

I have definitely read a lot about LED blueish lighting affecting sleeping habits

Manipulating the circadian rhythm with blue colored lights on free ways will help keep drivers awake.

New York City is slowly replacing all of it's sodium vapor streetlights with more energy efficient LED streetlights. 150w sodiums are generally being replaced with 91w LEDs. 100w sodiums are being replaced with 64w or 72w LEDs. Opinions vary on the quality of the light produced.

i wouldnt exactly call the blue light science questionable. most people, me included will have much less eye strain at lower k values. my eyes stopped hurting once i reduced the blue output of my monitors in dark rooms. i guess it boils down on the overall luminosity

Am I the only one that likes the yellowish glow of Sodium vapor lamps. I love it at night.

151k subscribers for someone reading a teleprompter.. Congrats to you!!

If you don’t understand how the microscopic parts of your eyes work this video will make no sense to you.

A great video again, I just wonder how the LED light, especially in the 5700K region performs in fog. The narrow band sodium is very good at cutting through fog rain and mist, where white light may be more prone to blazing, and that may prove more of an argument for 3000K led colour temp. Also, I would have expected there to have been development of electronic ballast's for most discharge lamps these days, pushing efficiency much higher, along with lamp life and start reliability. It certainly helped fluorescent performance in the 15 years prior to the led invasion. Cheers, and thanks for posting.

really interesting

White and blue light isn't good for eye health after dark though...

*tyler higgins* Sky what? You do realize nobody cares about that type of glare right? It does literally nothing to the average Human. Still my point stands, less street lights does not mean less light. On top of requiring generally more lights, you'll also find car lights much more annoying, as your eyes won't be adjusted to the light as they pass by. This in what makes car lights so bright while it a power outage.

You make absolutely no sense. Impossible to navigate in the dark? I'm talking about nearly every rural home having from one to many "insecurity" lights, that the vast majority are unshielded and cause glare and sky glow for many miles. This has a cumulative effect, there is no excuse for light pollution in rural areas. The issue is not "needed" light, the issue is light that is unshielded and too bright, that is what needs to be addressed. What are you, a small town city manager?

*tyler higgins* The reason we have lights in rural areas is because it's impossible to navigate in the dark. You need light to recognize roads and to drive safely. When you see a light, you look for something specific, that you'd usually see from 500m away at day. With lights from your car, you'd need them to be insanely bright to have the same effect.

*tyler higgins* Clare is caused by improper refraction of light, not LEDs and because LEDs are so small, refracting light tends to bo easier, as you can just spread the LEDs further apart. This is also why street lights cause less glare then car lights. You can either have street lights or more lights on cars, choose one.

And I did play after dark as a kid, but I had enough sense not to play in the street. There is no more "after dark" virtually anywhere without a light ordinance, everything is lit up like daylight with improperly mounted fixtures far brighter than needed. Even small towns and rural areas are now flooded with light pollution, that is inexcusable. What's it for, the half dozen pedestrians or vehicles that might be out between dusk and dawn?

Take your ignorance elsewhere, people in city around the globe are demanding the removal or rectification of "too bright" LED street lights. LED's emit white/blue light with debilitating glare, why don't you go find one that's 5,000k or more and try staring at it. That's a far cry from HPS lights that emit a yellow light at around 2,200k.

You've never been a kid if you haven't gone out to play ofter it's dark. -- Stop signs are "reflective", when they're place perfectly which is almost never the case. There's a reason why they place stop signs warnings on streets where people do 100 km/h, because otherwise they can't stop in time. -- That's a non-argument. The reason street lights work better then car lights is because they can be hundred of meters away and still visibly light up the street without being too bright. LED's don't emit "different light", there's only 1 type of light and the closer that light is to the sun, the lower accident rates, because it helps the brain recognize the road.

I clearly am a daily cyclist, including at night, that's what a head lamp is for. And just how many children are playing in the street at midnight? As for stop signs, I've been driving over 30 years and never not seen one with my headlights, because see they're REFLECTIVE. As for oncoming headlights, many of the new LED's put out such blinding glare they pose a real safety threat to oncoming drivers. Several online petitions to ban them nationally are in circulation. You are clearly an uninformed sheep, and part of the problem.

*tyler* It's statistically proven that lights reduce accidents. In fact I nearly blow passed most stop signs unless they have lights. It's nearly impossible to see whether there's a stop sign unless there's a light. On top of that there's absently no way of seeing children crossing the roads at midnight without lights. You've clearly never road a bicycle at night, if you think lights are just for fun. Lights are there to overpower other cars lights. When two cars are coming towards each other, your car lights are nearly useless to see anything on the street, which is what road lights try to help fix.

Matthew Bartlett i like that idea. Freeways should have blue light, but residential blocks and shopping centers should have more yellow lighting. Imo white light needs to go. It gives me migraines every time, which is arguably just as dangerous as yellow at night

Those of you saying curtains, light trespass needs addressed at the source, not at the expense and inconvenience of the homeowners, who also have every right to enjoy a dark yard. Even rural areas are now being flooded with glare and sky glow from multiple unshielded "insecurity" lights blazing from dusk to dawn, and even very small towns with no need of light, no pedestrian or vehicule traffic after dark worth mentioning, are now flooded with unshielded glare bomb LED street lights.

More LED's with the bright white-blue colors, just LED everything up! I read some article somewhere where one guy was sick and tired of the light bleeding in through the windows from the street lamps outside his house, and decided to make his own fixes to them by replacing them with LED fixtures to stop light bleeding.

While most of the scientific facts you present are correct, your base asumption about human night vision using scotopic (rods) is only partially correct, our eyes uses scotopic range when illuminance conditions are under 1 lux. Continue enlightening youtube with this great source of science knowledge!!

it surprises me that you are not stating the fact that LED lighting lets ALL wildlife think its day 24/7 and therefore disrupting their life and lifespan.

White power

Appropriately technically geeky! I really enjoy it


Why not use 5700K on highways and dual color in lower speed areas, 5700K from when the lights come on to around 10pm, fade to 3000K over an hour, and around 2am, fade the brightness down to around 70% over 30 minutes or so, where it stays for the rest of the night?

If you don't even know what sky glow is, you need to inform yourself, no wonder you make no sense. And debilitating glare does not only emanate from LED headlights (which need banned) but also unshielded street lights and improperly mounted "insecurity" lights. "Does literally nothing to the average human" the AMA disagrees with you. Google and read their official policy statement on LED's, if you are capable of grasping it.

LED's have definitely improved in the last few years. One of the things I like most is the higher color rendering index (is the 90+ thing a type of standard?) of modern LED's, and the Philips warm glow is nice as well. LED filament technology makes for great decorative bulbs, and some companies are back to using glass envelopes. But right now, long term reliability is still less than I was hoping for.

since eyes percieve logarithmically, change the y axis to logarithmic and you will see the difference is much smaller than it seems. Also, consider the contrast between dark background and less stimulating sodium light might be easier for driving and seeing things in shadows,than the high contrast of the much higher stimulating LED light.

The problem with light pollution from various light sources in astronomy and astrophotography is a bit more complicated. Yes, the low pressure sodium is by far the best option in this regard since it can be filtered out fairly easily. But even high pressure sodium is still fairly OK, because the light spectrum of a HPS lamp can still mostly be filtered out relatively easily as the most of the light output is still concentrated into a few wavelength "spikes". So you can filter out a considerable amount of the light pollution produced by a HSP light source while mostly not affecting the rest of the spectrum by using a very selective light pollution filter that only targets those spike wavelengths. It's not ideal, but it still helps tremendously. Meanwhile the color spectrum of an LED light, no matter what it's color temperature is, is a lot more continuous and can't really be effectively filtered out, because by doing so, you're also filtering out the parts of the spectrum you want to keep. So, as an amateur astronomer and astrophotographer, I have a love/hate relationship with LED lights replacing the HPS lamps. I love them because most of the current LED fixtures, at least when installed properly (which is something that doesn't always happen, sadly), seem to have a much better design that tends to limit the light pollution greatly. But I also hate them because any light pollution created by LED lights is effectively killing astronomy and astrophotography. We've already been struggling under HSP lighting, but we could work around the issue in a fairly acceptable way. WIth LED-based light pollution, there really is nothing we can do except travel very long distances to the few spots still untouched by light pollution :(

The greater density of up-facing light sources in the vicinity of the airport may be useful for navigation and ground recognition by the pilots. So it's not 'all' wasted light.

This is some really good shit to watch high

Warning: Do not watch this on 4 hours of sleep when you only know enough of what he's saying to get you into trouble

Mercury Vapour FTW

Sodium and other non-LED lamps, with their spread, have less defined shadows - I've noticed driving in residential areas with lots of trees that the high contrast between light and shadow is much more fatiguing on my eyes than sodium's ambient glow, which also makes it easier to see things out of direct light.

I remember the last time the circadians came. They made such a noise and people actually fried them and ate them!

Why on God's green earth are ANY street lights needed on a highway, let alone 5700K? Why not just dispense with headlights in that case, and just burn out everyone's eyes with a laser.

Why not have both? I.e. 3000k leds for in city roads and 5700k leds for highways. Seems a good compromise.

No thanks. Leave the HPS Alone. The LED are annoying and hurt my eyes. Seems like watered down light. When HPS give a nice warm light and nice and seem pleasant to me.

I've seen LED fixtures in parks that dimm when nobody is in the vicinity (using simple motion detectors). Also a smart way to reduce energy usage and light pollution.

This man needs more subs.

I think there's more to this than just the light source. It's also the color temperature of the light itself. The reason I say this is because traditionally, your sodium lights (and I admittedly know nothing about the difference between high- and low-pressure sodium lights) emit more of a yellowish light. Even in your highway clips it's very obvious that the sodium lights skew more yellow and the LED lights are a harsh blue. Okay, maybe I'm being harsh by calling the LEDs harsh, but that's typically my experience at night. Lights that include more of the blue in their spectrum have long been determined to provide lower contrast than more yellow lights, and I believe I see that in your highway clips. While the LED lights may be brighter overall, the detail of the objects you're looking at are more enhanced by the more yellow lights. Please bear in mind that I'm a person with rather sensitive eyesight, and I always prefer less light to more. I use my computer in my living room on my 40" TV and I keep my overhead lighting at a minimum, while using a combination of yellow-ish lights and red lights (thank you Philips Hue) while also almost always turning the brightness of my TV down all the way. In fact, I switched Firefox to a dark theme and use a Youtube extension to do the same and I still feel like I'm bombarded with a ton of bright light. I'm comfortable typing this right now, but if I go to a standard website I'm going to be blasted in the face with a bunch of light that is not going to be very comfortable due to the widespread use of white backgrounds (it's the most idiotic and annoying thing, I don't understand why a black background isn't the default). But my point is that at least for some time (I'm not sure if this is still a thing), fog lights in France were required to be yellow. Why? Well apparently because it helps increase the contrast of what the driver is looking at. That was a revelation when I read about that, and from that point on I realized that I vastly preferred yellow light at night. It's because it can illuminate things and outline objects without being obnoxiously bright. In my experience, this is a thing that makes a difference in my nighttime driving. Similar to how when we'd go to sleep at night in boot camp, they'd turn on red lights so that the people who were awake could see without disturbing the people who were sleeping (at least somewhat, it would bother me on rare occasions). I probably did a terrible disservice trying to explain this while somewhat inebriated (shut up, it's the fourth of July), and I'm not really filling in the gaps properly, but there's something to the aspect of color temperature of lighting and the contrast that people are able to perceive. I don't believe white LED lighting is the correct choice for illuminating roads.

I left my comment early and I think it's quite obvious that you covered everything I mentioned. So, sorry. I will mention that there are night modes for many computer devices including iPads and now even Windows 10 includes this, in which it reduces the amount of blue light that is emitted. It's not so much that blue light is harmful, but that the blue light seems to provide more of a strain to the eyes when concentrated in a particular area. So given that, I'm entirely open to the fact that I'm probably wrong regarding highway lighting. All of this stuff is very fascinating.

Yes make st lights led

the power company replaced our yard light with an LED last winter. it's like the sun under the thing! but you can't see it from the end of the driveway which is odd

I have 3000k led with 90l/w , fixtures from 70-150w from reputed brands.

This is an interesting topic that I didn't know a lot about, but always had a lot of questions about. This filled in a lot of the blanks, but not all of them. See, I live in the Detroit area, and we've had HPS or mercury vapor bulbs in our lights forever and they've just recently in the past couple years got around to replacing them with LED's. On the freeways, this is great, you can see everything clearly and it makes night driving much easier. However, in the residential areas, the street lights are worse than ever before, they only light up what's directly beneath them, which makes seeing people who are in the street for whatever reason almost impossible, and the sidewalks are completely dark which has a slew of other potential issues associated with it. Roads paved with blacktop are impossible to see, it's like driving through space on acid! Areas with frees are extremely dark now as well. The old HPS bulbs had a worse color but they had better light distribution for all of these sorts of things and they made more sense in our residential street lights, imo. I just can't understand how the LED's are so great for the freeways but so completely terrible for lighting up my road...

What is your stance on the idea of solar roadways as per this video?

Moonlight and starlight are not blue. They look blue because blue cones are the last to flame out in low light. Look up Purkinje effect. Further, blue light is not focused in the eye along with red and green. It falls short of the retina.

Light pollution is not just an aesthetic issue, it messes up animal migrations plant reproductive cycles, and well there are my brain dead neighbors with unshielded porch lights glaring in my eye from 100 yards away.

Don't need either type of light pollution and energy waste, cars have headlights. I've driven numerous streets with so many street lamps blazing away(and few to no cars) where I couldn't even tell if my headlights were on. (turned them off and on could not see a change)

Outstanding video. Subscribed.

Is this supposed to be about LEDs or every other type of light?!

i think that the circadian disruption is more desirable as people are more awake therefore more safe during the drive.

Led light more bugs (depending on the brand ,since flying j model still have bugs but the one at petro pass i401exit 48 in Ontario has zero bug since they put their new light !13 km from there you got a flying that is a bug magnet !the guy managing this issue ?when I told him the solution he was gona go check out what the other truck did

Eventually with the tech in smart cars, we should be able to light the next half mile or so in higher color temp so you can see in front of you, but then have it revert to a lower color temp "standby" state. That way you get all the benefits of safety with minimal circadian disruption for locals. Also, would just be able to tell a car is coming by the lights changing color

Replace streetlight with LED light is a really good idea, but what about in bad weather condition such as fog or heavy rain? beside the efficiency, I think there's other main reason of use the yellow or orange light as streetlight is because longer wavelengths light can travel longer distance in bad weather condition. White LED light might not as safe in those situation.

if blue light does hurt your eyes is just fear mongering, then why does the 650lm osram lamp with 6k kelvin leaves black dots on your eyes while looking at it and the 900lm osram lamp with 2500 kelvin doesnt? both are mercury lamps with the same socked type and same generation.

When I drove a taxi people didn't believe that I saw better without my headlights than with. I figured that out when I forgot to turn the lights on after leaving the depot. The Light from my headlights would shine back in my face making it more difficult to see because of the light colour. They would ask what they are for if that's the case and I told them it's so other people see me, not so I see them.

Aaaand... Where I live they use CFL on roads

Light pollution might be wasteful but it's also important for aircraft in emergency situation to avoid populated areas at night. A populated area that isn't identifiable until you're a few hundred feet up with no engines doesn't allow enough time to avoid it.

I can't see shit when someone has those blue leds aimed at me

I say we just go back to cicerone lamps.

I'd say LED's in the 4000-4500K range would be the best compromise. Not too high color temperature, and still much more efficient than sodium vapor lamps.

Very good video with good data to back it up. I think you presented a really good case for the benefits of LEDs to anyone who might have doubted or disliked them. When I first came across this channel, it was through one of your retro tech videos and at first I didn't think you'd be that open to change and innovation. The more videos I see from you the more I can tell you look at both sides and then objectively make your decisions. This video series about HPS vs LEDs and the one on EVs was really the tipping point for me to subscribe. Keep up the good work! and I look forward to seeing more topics, about technology both new and old.

I vote we simply get rid of all outdoor lighting and let peoples eyes adjust to the dark.

Great video. I'm feeling old though as I remember as a first year Electrical Apprentice that we started changing out Low Pressure Sodium for new fangled High Pressure Sodium...


Blue should keep drivers awake better. +1

Idk I love the ambiance of sodium lighting. Feels cozy to me

BRUH!! Props to all tha research! How long did it take to gather all that data?! I've been developing these RGB LED Beam (halogen replacements) liquid cooled lights for 3yrs now. The main function is to have a headlamp in your car last longer than the car at 15 years, and change to FOG yellow automatically!

I find that LED headlights are way too bright and temporarily ruin my night vision, much worse than old-style headlight bulbs (not sure if these are HPS or not, but that's not the point of this comment). How is this safe? Perhaps white LED gives better vision to the driver of the vehicle because they are not directly looking at the light source, but they are more dangerous if they cause other drivers temporary blindness. While headlights were not covered in this video, nor was the effect on night vision of looking directly at the LED light source, only looking at an area illuminated by LED light (as the streetlights are in the periphery of drivers' vision - not so with headlights). I feel that this is an essential aspect of the topic, and not being covered deeply flaws this video. Obsession with efficiency is not a good thing.

I like the bright white LED, 5000k and up.

Give me back my INCANDESCENT bulbs! Your lighting technology with LEDs is BS! Your just selling or promoting LED lighting systems. Next you will try to sell us "solar panels" and tell us how great they are too!

In all, it seems a mixed methodology of light fixture deployment and control should be used, with LEDs capable of altering the temp and output dependant on several factors, with their longevity being a main pro over the initial installation cost versus replacement/repair costs of other fixtures.... if there are any. I dont actually recall any street lighting on non-highways being replaced... or out at night. but its not a detail I would notice, I dont think, unless several in a row were out. Like you said, a lot of the housing fixture is responsible for the light pollution - your 'see it from an aircraft in flight' bit. so a combination of housing that restricts how much *direct unreflected* light is lost going up, combined with the already lower amount of power to put out the "same level of ~visible~ light".... and I'm sure the melonoptic thing wont be as bad as the figures suggest. Afterall, if only what - 10 percent of the HPS light is even visible, then an LED which produces twice the 'scop' light at 10v, but say, half of that at 5v, and same scale on the melon bit, but at 10v it still only produces twice as much melon light as the HPS, then that 5v led is producing the same level of both light at half its power capacity... and with the right housing solution, might not even need that for an even and safe level of lighting. THEN add in, maybe, a timed system, with long stretches of highway that have no junctions (so basically on a highway, the sections between that are just 10 miles of straight road or something), after certain times, every other light can be switched off after a certain time, cutting power cost down to a quarter... And if a simple, low-power-and-low-cost system could exist, then the lights could even be only on when cars and trucks actually drive down them. Here in the UK, some motorways actually do have their lighting completely switched off between certain hours because of low levels of usage or somesuch, so that's also an option. A combination of all three? (whatever-time to 11pm, all lights on, set to a less-circadian rhythm-disrupting spectrum. 11pm-1am alternating lights off and on set to the blue , 1am-4am switched off, 4am-6am alternating lights off in blue but with sections where the 'on' and 'off' from the previous alternating timeslot is switched, so the lamps see an even distribution of being on.

I really hope they can get new LED Street lights to have the same orange color, because it makes me feel safe. Even though blues are more visible during the night, it feels really fake and artificial.

I only care that we stop wasting energy by having light directly bleed into the sky. It should only be reflected off the road.

I'd get rid of the vast majority of street lights and leave them only at intersections and pedestrian zones (like parking lots). The incredibly good white LED headlights in my car have rendered normal street lighting along roadways unnecessary. The street lights that remain I'd put on fade-in fade-out motion sensors. I'd ban "up-lighting" altogether and require 100% of new outdoor fixtures be "full cutoff" fixtures, including the ones on walls.

Yes. LEDs use less energy. Video over.

I really prefer the sodium lamps. The light of the leds are tiresome for the eyes.

You can still filter out high pressure sodium light. Deep sky images are usually taken with narrowband filters letting threw only a few nm of the spectrum. Hps has the advantage of having sharply defined spectral lines, thus are easy to filter around. Where as LED's are braudband sources that will create sky glow even in narrowband images. Hence why i hate them.

This video is impressive.

Uh now I get why the new modern road construction site lighting are green here in Germany, and thinking about it you see everything even at high-speed.

Seems to me a 4000k led would be a good compromise.

Thanks, great video!

Great. But maybe a little too long video.

I disagree. The length of the video should be set based on the content he has to provide, not shortened just because YouTube views have short attention spans.

Why couldn't we use them in conjunction with one another but in a more coherent way than the one guy suggested? That might work

I believe it is because the rod cells are more sensitive and fatigue faster. This form of fatigue is not harmful, but does need to be taken into account when choosing light sources. You need less light in the freq the rods are sensitive to.

Then you can pay to run them.

It is not useful because it comes directly from the light source instead of from the object that you want to see.

Of course a street with people who live nearby should maintain the warm light as well as the aesthetics wouldn't interfere with safety in LTZ areas, but the safety and efficiency brought by colder lights is really nothing to scoff at. With both greater lighting and a more reactive brain, along with proper directional lighting you can be at the edge of a suburban area where the white lights start and not be affected at all by the thing.

tyler thanks!

I think you are focusing on a one-color-temperature fits all solution. I think they should have 5000K+ lights on highways, freeways, and high crime areas, to increase alertness, reduce drowsiness, increase visibility, and security. They could have 3000K- on residential streets. As the cost of variable color temperature lighting drops, having the color temperature on residential streets drop after 9PM seems like a plan. I know that personally I have 5100K lights in my work area and in the evening if I am not trying to work late I drop the color temperature in the house to 2100K. If you really want to kelp people's melatonin levels, ban those evil blue led pilot lights. I put red filters over all of them.

Bert0ld0 contact your city manager, request that the light be shielded. Street lighting belongs on the street, not in our yards or through our windows. My small rural town is putting LED bulbs in barnyard style lights, horrific light spill and glare everywhere. They finally shielded the half dozen that were issues on my property, after some miscreant shot them out.

I agree, LED for sure is the future. But Tech Conn is actually correct, they put a cold LED street lamp pointing to my windows and apart from the light pointing in my eyes I find it a lot more difficult to fall asleep. I'm going to contact someone but I don't know who

I agree with that, I went on vacation not to long ago and was riding my motorcycle at night... The Tampa, FL area has pretty much all gone the "blue" LED street light way. I was able to see so much more, the people on the roads seem to notice me a lot more. Also as a side benefit, I never once felt that ting of tiredness you get at night when things are dimly lite.

I came across this by accident and like it a lot. Great research, thank you. I am now subscribed.

maybe its just because my city usualy buy cheap led, but some colors seem to kinda dissapear with led. like yellow... wich is a problem when most thing that you can buy to be more visible when on bike are yellow.

It took me the whole 21 minutes to cum. But I'm proud that I got there in the end...

Your argument is flawed about sensitivity. The change doesn't happen based on day/night cycle it is based on brightness of the light there are 3 colors of light ast most airports...can you guess what color is used is the brighter areas?? KNOW why they do NOT use BLUE light on navel ships??

What kind of pronunciation of efficiency is that lol

I had to move to the country to see the stars. My daughter freaked the first time she saw the Milky Way at age 12. It is a shame we can’t be bothered to preserve the night sky.

Go vegan.

I love the golden light of our current street lights. The blueish LED lights look garish and give me a headache.

Don't change anything I HATE CHANGE

I have always found the orange light from sodium vapor lights to be irritating and create horrid aesthetics. I think white light at 3200k look the best but 5600k is pretty nice too.

Why wouldn’t you want to keep people awake while driving? Seems like a perfect time to interrupt their sleep rhythm.

Dear me, I thought it said “should IEDs light the way”

I use 5000K for everything. Every light in my house is 5000k, even my cars HID headlight bulbs are 5000k. Hell even the interior in my car uses 5000k. I think it might have to do with our childhood being the sole reason why people prefer orange light. I feel the closer we can get to the sun's color temperature, the more accurate colors look and also helps with mood. I think a pure white light makes dirt and clutter more obvious and really makes a poorly decorated area look even worse, but that's not a fault of the light in itself. I have warmly decorated areas in my house and the last thing that comes to my mind is "hospital lighting". But to each their own. We turn off our lights an hour before bed.

Need to consider the fact that there is actually value in disrupting a driver's circadian rhythm. Driving is a high-alert task and seeing blue light at night shifts your circadian rhythm towards this time, meaning you're more alert at this time. For regular night drivers, this is actually very valuable and can see no reason why this wouldn't be a cause for much safer roads at night.

Whether the cooler light is safer or not I hate it. It takes me 2 to 3 hrs to get to sleep now since the lighting at work was switched from HPS to LED. There have been no other changes in my life style other than the new lighting at work. I'm considering retiring 10 years early just to get to sleep faster. I only use halogen lighting at home and most of the lamp shades are an amber-ish color to compensate for the LED junk at work.

I miss the golden glow that the sodium lamps gave the city as you were flying into the city at night. I wonder if the transition to autonomous vehicles will reduce the need for street lighting.

0:55 ? No I don’t remember you saying anything about that

Used to be known as high problem LEDs make sense as they save $$, while costing more

Very interesting video. Thank You


Blue light may help to prevent tired drivers from falling asleep at the wheel

LED's probably more expensive, prone to fail quicker, what on hot ass summer days if cooling or other elements aren't working. plus they flicker unlike the sodium lamps. Yet we got some roadways in europe with green LED lights.

They replaced my street lights to down facing LEDs couple years ago. The down facing has focused the light more on street than the sidewalks. Now pedestrians walk in dark, harder to see them when driving, I found myself high beam for safety. Walking on side is also scarier cause who knows what could be around the bush. It's just too much down facing, doesn't create any bounce light to light the whole area.

Fuck that, "safety"? It's night, people aren't on the streets, they are resting to work the next coming day. Putting shit light to disturb a driver's eyes and brain to fool them into thinking that's day time is only gonna create stress and fatigue to drivers therefore that's against the safety of people in the streets and other drivers

0:15 hey i know that road

Great content, but a bit repetitive. Could be much shorter with fewer pitches and repeats of points.

this video was done very well!

Especially at this time of year when even down south here at 56°N it doesn't really get dark at night, I just don't think that the LED ones help. Under sodium lighting colours are distorted but everything seems more "contrasty" - but under LEDs I just find it really hard to see. Weird, because my car has LED headlights which are a bit blueish but a hell of a lot more effective than the halogens they replaced.

This is a brilliant and balanced conversation on the merits and downsides of HPS vs LED. I would comment though that based on the % blue light output, 4000K lighting would be the ideal fit as it so closely mimics moonlight's 27% blue - you get the best of both worlds without undue excess blue, and still getting decent efficiency gains. Nicely put together - keep it up as I really enjoy watching this channel's insightful and educational content :)

It might be worth looking into WHERE which lighting it used. You might want low melanopic light streetlights in neighbouroods. 1. People live next to the lights and 2. because of what the area is used for, it should not really have a lot of late-night long-distance travel. While you'll want high melanopic light in commercial areas and on speedways since 1. few to no people live next to them, 2. they see more late-night long-distance travel.

Autunite the warmer color temperatures have become more efficient lately and the current trend is 4200K for municipalities, somewhat mimicking moonlight, and 3000K for residential side streets. 2700K is quite warm, I have seen this only for some city parks and outdoor restaurant common areas.


Too long

I feel like safety is most important so side effects aren't as much of a program if it helps safety. Having driven at night on highway with no lights it (as an example of less safe lighting) I see it's super scary to drive in bad lighting and can see lots more accidents happen.

There is one other issue. That of CRI. You can LED fixtures with a color rendering index of upwards of 95%, well designed HPS systems can get to around 25%

this video sure shed some light on outdoor lighting.

i agree with most of what you said in this but wouldn't disrupting the circadian rhythm at night improve safety by making drivers more alert? which would make led lighting the obvious choice just an observation lol lights help keep people from falling asleep at the wheel. How wrong does this guy think this is?

Just lighting the road is not safe. I want to know where to phyco bitches with the axes are to the sides

I really like the look of the orange lights

Yes helping to fall asleep at the wheel is good

Anyone who has done night timephotography knows that daylight and moonlight has about the same white balance @ ground level. Do a long exposure image under moonlight, and the colour balance of your subject looks approximately colour balanced like daylight. Use the colour eye dropper tool in any decent photo editor and you can confirm this. Under darksky, a least 100kms away from a city and no moon conditions, the sky can look a brown colour, sometimes blueish, all from the same location, just different atmospheric conditions. Truck drivers have done many, many tests, and truckies are more likely to spot a roo using slightly warm, eg 5000k hid lights in their trucks. The cheaper 6000k and above hids are avoided by truckies. Many many tests have been done. The reason people are reacting quicker to led vs hps, is not the colour temp, it is the wider CRI of the led, and makes seeing the typical black suv easier. All the cheaper leds have higher colour temp, eg 6000k and above. This is due to how leds are constructed. Most leds are actually blue, but are suurounded by yellow phosphor that is energised, and re-radiates at a lower colour temp. Very low colour temp leds, eg 4000k and lower, havenreduced efficiency due to the real estate required in the led chip to accommodate enough phosphor to achieve this colour shift. I have made high power bike lights (for night trails) using 100w led street light chips of various colour temps. You can clearly see the additional yellow phosphor of the warmer (lower k) chips.

in minneapolis mn it is not uncommon to see lights shut off when there is no traffic and only turn on as vehicles pass under them. you can watch entire road ways turn off and just light up as a single car drives down the road

Yeah I agree, the LED colour aren't great at night, I prefer the original colour of the condescend light

My biggest issue with new LED lighting fixtures is basically what you mentioned at the very end of the video about the driver and the heat sink. All these new fixtures are basically a whole assembly with no replaceable elements in them, forcing you to replace the whole thing. I'm also in Chicago and have already seen city installed LED light fixtures under bridges have entire LED strips go out (1-2 of 6 strips). Combine that when some do fail they flicker/strobe while doing the death dance. I love LED tech and think we will find a good compromise in the future for output/color soon. But the maintenance and cost I don't think factor in the supporting electronics going out. The LED is rated for 100k+ hours of service but all 2 common to see them fail in 2-3 years, even in household bulbs. I would love to see them designed with replaceable elements within the housing. Also, just found your channel today and you have a new sub!

So you believe everything that people say?

Those poor amateur astronomers who were always able to filter out the narrow band of HPS light in order to see the stars. LED can't be filtered out to leave other visible light.

One thing to consider is the CRI of an LED nearer daylight temperature is going to be far higher. This very likely contributes a great deal to the visibility increases claimed.

mad respect for your researching prowess... very unoften do i come across individuals or channels that i feel took the time needed to understand all aspects of a topic.

LED lighting is absolutely horrible. My eyes hate seeing that monstrous form of "light."

I think you should do some research on the effect different form of lighting has on the eyes. My eyes are fine. LED light that he's talking about uses a very narrow band of visible light that is not great for your eyes. The guy in this video mentioned the "harshness" of the light. That's one way of putting it. Perhaps you'll research it and find medical issues with this type of light.

See a might have eye issues that are causing it.

There is only one light which can beat LED in efficacy and thats Ceramic Metal Halide (CMH), its different from Metal Halide as its under a much higher pressure.

No shit! I-88! You're around me my dude! Edit: As you may know, people in Illinois hate using turn signals. Just a funny; with cooler lights, this will mean that Illinois drivers (and BMW drivers) will use their signals less because they'll assume that we'll know and see them switching lanes/turning.

Compromise with 4000k led

My goodness...! Thank you for not choosing Wikipedia as a source! Finally a legit indie science youtube channel.

No at night i cant see blue. It gets so terrible it blurs out

It looks like evolution is working and your line might end and make those who life less weak by including your weakness

I miss a comparison between the spectrum of white LED's and the night vision: because those relate badly as well. White LED's are basically 430-440 nm blue LED's with a fluorescent layer emitting at, guess what, 588 nm, the Natrium (sodium is an ugly word, sounds like toilet cleaner pfff.) point. So our peak sensitivity of 520 nm, the output of a White LED is very low! If you want to save the world, we should lit streets with blueish-green 520nm LED's (not yellowish green as that type is highly inefficient). Another thing missing in your test: most LED fixtures right now have low frequency switching power supplies. Around 50-60Hz (grid frequency). That is REALLY annoying to you eyes, the flickr give a lot of strain. So 520nm LED's with 10khz switching PSU's are probably best. Added benefits: woman look less attractive (less rapes) and burglars really have a hard time seeing details of worthy stuff. On the dimming: here they shut down interstate lighting after 20.00 as the traffic peak is over by that time. So at 20.00, pitch black night returns.

If they use yellow LEDs I am down. I hate blue/white light at night, it doesn't feel natural.

Goodbye ugly orange lighting. good riddance.

tnprime good bye to not adding to falling asleep at the wheel

I really, really like the video and video style. The video actually feels like someone with at least a degree in the field, if not a thesis on the specific issue, contributed. Lots of interesting information has been nicely condensed and mixed with good illustations. It's not at all dumbed down - at least high-school level of language sophistication and science background in the viewer is implied; it's in the small thinks like you didn't explain color temperature and what for example 3500k meant - and how you expect the viewer to be able to read a Cartesian coordinate system off the original sources. And there's none of that horrible, horribly distracting and condescending fad to show you the same text on screen that is narrated. Nice sources, and I like the all-angle approach instead of the "edutainment" 4-minute monochromatic view at an issue. Well done, I subscribed right away.

I hate yellow sodium lights. They remind me of communist times.

No because they are blinding drivers with 20/20 vision.

As another comment has said, more disruption with circadian rhythms is a good thing for safety. So why not have a balance of them? Have the bluer lights on long motorways/highways/interstates, and gradually have warmer colour temperatures as you get closer to the city. Leaving the city nice and warm so people don't have blue light shining in there windows when they try to sleep.

I think less serotonin production is a bad thing in urban districts, but on highways a cooler light temperature is effective against sleepiness and could prevent accidents.

Great video!

It's funny you should mention that about the bluer lighting. When I was a kid the street lights were a lot whiter and bluer, and I always thought those made it easier to see at night.

My brains are hurting

yscar reviews please see a're nuts

The red dots mitochondria are the powerhouse of the visual receptor

A few years ago they changed all the street lights in my old area to LED and I couldn't stand it. IMO it was far worse than the soft yellow light. Since being brighter, it seemed to cast harder, pitch black shadows. Where I could stand on the street before under the light and see somewhat decently into my backyard, it was now a complete wall of black. Maybe it was because the light was right in front of my house so I was getting a much stronger effect, IDK. I just know the whole block seemed darker to me because anywhere the light didn't hit was an almost pitch black shadow.

The advancements in sleep technology (such as alpha-wave emitters) might make the entire concern of circadian rhythms a moot point...for humans. The potential for disrupted wildlife (especially avian species) is a real and active concern. Many of my local HPS lamps have been replaced with LEDs, and the birds chirp all night long (particularly the mockingbirds and scrub jays).

This video is worth watching a few more times, and the links it provide is worth your time a bit more.

About light pollution, you are right about low pressure sodium, they have two narrow spikes. The same could be done using LED's tuned for a few spikes around 500nm.

Like in music there is alway will be the one whining about coldness

I find that the white light helps keep me awake while driving. Driving on unlit motorways being the worst for making me feel sleepy and the orange lights while still being bad are worse for making me sleepy than white lights. This is my personal findings tho

I've never seen a channel literally go into detail on lights. Subscribed. I'd love for more on literally any topic.

Omg!! Yes or no ?

why do we use street lighting. answer to prop up electrical companies. because it never should be the drivers responsibility to avoid a pedestrian when a vehicle is moving at night. street lighting should tightly controlled only used at approved street crossings and very limited a vehicle merger points. a diver should not be held responsible if a moron cross in the middle of a block because he/she are to lazy to walk to an approved street crossing. So how much money is the Local County state and Federal throwing away each year on electricity and maintenance of street lighting? A limited access highway has very few hazards. and everyone should remember driving class 101. Speed limits are set are for picture perfect days. Add or subtract anything from that kind of day IE night your speed should be reduced. Sorry for the rant I know this video was about. which light is better but sometimes the government steps in too far.

Hmmmm...this video seem to be filmed in Illinois. I see you Pace bus

Great content

Seeing as we're going to have self-driving vehicles the real safety question is what do the cameras see under these light sources? Couldn't we just give the cars night / starlight vision and get rid of highway light pollution?

I don't like light pollution blocking out the night sky. Keep the older lights.

LEDs produce less wasted light pollution too. Notice the ground get lighter amd the night sky get darker, a win win for everyone.

Seeing the milky way on a moonless light in a dark environment is awesome!

12:41 The "hot spots of light you see from above here" is most likely an LED retrofit - the poles were already there so they had to work with that. There may have been HPS cobra-heads originally, which as mentioned throw light into the sky, but probably had a wider spread and didn't make hot spots, or at least as not as bad as what is seen now. Yet another tradeoff - no uplight from the fixtures, but the hot spots make for an awful Uniformity Ratio, not to mention an annoying "strobe effect" when driving.

9:35 "none of it will wind up lighting the sky" - sort of, but not really. Not mentioned in the video is the THIRD contributor to uplight - light bouncing off the ground! Tradeoff? Light colored pavement which makes it easier to see, and less light & power is required, but light bounces up into the sky. The irony? A full-cutoff fixture is specified - all that engineering and the parking lot is basically a huge reflector.... Rebates are sometimes given for "Dark Sky Compliant" fixtures, but I say the rebate should not be given until after a site inspection is done... light pavement? No rebate.

And what about penetration and other properties of light dependent on its frequency, for example how well does the blueish LED generated light go through fog, snow, rain, etc. compared to HPS reddish light?

Two notable points regarding the color & color rendering of High Pressure Sodium: Upon inception of HPS, there was an increase in automotive accidents at intersections. The theory was that the traffic light's yellow caution light got "lost in a sea of yellow lights" and all of a sudden the traffic light was RED. BAM. (HPS not really yellow but close enough to confuse drivers.) The second problem was noted on police reports - all of a sudden, every car thief on the police report was wearing a dark blue jacket.

led bad for the body............

People buy and download yellow lights for sleep. PC software tints the screen yellow at night so you get tired. Yellow reading lights are good before bed. Yellow backgrounds are available on ebook readers and ebook apps. Having this nice sleep-inducing yellow lights on the road at night is something I would pick if I were trying to come up with the worst lights for the road. Its funny that at some point people actually put time into figuring it out and ended up on yellow. Though admittedly, the white lights seen in schools and hospitals are pretty bad too and wouldn't make a great alternative.

I like HPS more as they produce warmer light and less headaches

This sucks shit if you break down

yeah, and most of the new lights are not as "blue" as claimed. Manufactures have gotten far better.

i really dont see how the lights that come on at night and DONT distrupt your body telling you "oh hey sleep time soon. better get to bed" is a bad thing. the current lighting used in most places that barely light and fucks with your bodies natural functions is a problem. if youre one of those people whos body produces melotonin when it gets dark rather than when you want it to, you shouldnt be out driving anyways.

I find that having white light street lighting has a detrimental effect on spotting approaching vehicles on suburban streets which have cars parked. Having the street lights orange means that when a car approaches, the increase in white light allows you to spot the projected headlights before you see the vehicle itself, even around corners and reflected in the paintwork of the parked vehicles. With white street lights, the headlights disappear into the rest of the sea of white light, meaning that the approaching vehicle will actually be seen later. At least, that is my experience. I don't doubt the other benefits, but this loss of contrast between vehicle lights and street lighting is not mentioned anywhere.

How convenient that all High pressure sodium light manufacturers make enhanced spectrum bulbs that allow is to see better with zero added cost per bulb , unless you've owned and operated 50,000 watts of HPS lighting for the 14 years I have don't bother with the LED nonsense which is a massive expense , there are no maintaince expenses with high pressure sodium lighting , especially magnetic ballasts that last 30 to 50 years ,

this is a good analysis

You are impressive.

Problem is when oncoming traffic is passing in a narrow lane street and their hyper bright LED light is making it so I cant see a damn thing.

Eye fatigue isn't good for safety. And that's what 5700k does for me. I'd rather drive in the dark. Still, I suppose it's OK for short stretches near cities.

PC amber tend to be the best choice for public lighting as they present the optical benefits of LEDs while producing less light pollution than bluer LEDs. Also, about your point that the reduction of power counteracts the increased of light pollution from white LEDs, it doesn't. The power reduction is much less than the increased effect of white LEDs.

Interesting video. Lots of information worth considering. On a personal note, we are on different sides of the esthetic question ... I prefer the bluer, whiter lighting. Hated the switch from mercury vapor to sodium. I welcome the switch to LED’s currently underway here in Maryland.

This skyglow you talk about, the examples you have make it seem like it has more to do with the fixture rather than the lighting source itself.

LED straight up give me migraines i fucking hate them

I prefer sodium. It puts me in the mood! :)

Why are there zero "glancing blow" impact craters on the moon? How could every single impact be due to perfect perpendicular trajectory? See Brian Mullin's Cool Moonlight Experiment & Theory March 23, 2016 ?v=U2rRQXeqKLk Relates to physics, biology/perception, light, lux, lumens, physics, Jesuit-controlled western psyence.

Hot water freezes faster. Moonlight is colder than moonshadow. We do not understand light because physics has been misled Psyence dogma. For example, all "sides" of the "globe" theory were Vatican-controlled. See UNSPUN episodes from #110 onward, or anything from Johnny Cirucci. See also Brian Mullin's Cool Moonlight Experiment & Theory March 23, 2016 ?v=U2rRQXeqKLk

19:21 in -- "peer reviewed" means controlled, closed-minded -- see youtube UNSPUN #119 to learn all about the Royal Society as a centuries-old control mechanism

Soon it won't matter so much because AUTO-UBER driverless vehicles will become predominant, as driver-owned and operated vehicles are "phased out" according to UN's AGENDA 21 and AGENDA 2030 Draconian intentions to disempower individuals and limit travel. Look into the coming Neo Feudalism. Google "car-free sunday rome" and see how the man-made spectre of "smog", having entirely vanished from LA and all USA media, is now being made the boogeyman in Rome.

Surely disrupting circadian rhythms at night when driving is a desirable thing, since it is not good for drivers at night to fall asleep while driving.

Personally, I feel that tis lighting which causes wakefulness is a positive, and that ~6500K temperature is pleasant, so I see no tradeoffs. As long as your opposing view argues that there are only minor tradeoffs, then I think we'll be in a good position to put this tech into effect immediately. As soon as I saw that clip shre you drove from a sodium lot road to an led lit road, I was sold.

I don't think the street lights are much of a problem.. Now those LED headlights? They need to go. High beams or not, they almost always blind me as opposed to the older bulb style headlights. I've had this discussion with a lot of my friends and family, and they all agree.

I live in the UK and my town is slowly getting relplace by LED but my town is mostly full of sodium street lamps that are like longer have and thin bulbs that light the road and sidewalks but the Led just lit up the road and hardly the sidewalk.

Awesome video, eyes started glazing over at about 16 mins with all the numbers. I didn't like the change from warm incandescent to cool led down lights at home but now 6 months on and I like it. Also, since blue light disrupts circadian rhythm this should keep us awake better whilst driving thus less accidents from fatigue.

I watched this video because a friend said this guy was into lights... it’s intriguing to a point where it’s hilarious

I would have liked to know how long the various types last and what the replacement costs are. Also, are any of them temperature (weather) sensitive.

I like the cool light. I hate using warm light bulbs in my living spaces. I can't stand light of less than 4,000K

One word for having sodium-fog.

As always, well researched and presented.

If the orange lights make you more prone to sleep then the blue higher temperature LED light source would make drivers MORE alert which is what drivers need to have MORE alertness!

Screw it LED'S all the way.

This actually explains the varied lighting temperatures of the streets in the video game Cities: Skylines. All large roads and highways/freeways had higher temperature lights, whereas 4 lane divided boulevards and small 2-way residential streets had low-temperature lights. I think this mixed usage of light temperatures is perfect and makes sense. I'd rather have my circadian rhythm messed up when I'm traveling long distances via large roads and freeways and then as I approach home, enjoy the pleasing effects of warm temperature lighting. Perhaps my home should be setup in such a way...

Sodium vapor lamps are a very different color than an HID lamp used in cars. The Na vapor is old technology and isn't actually considered "high intensity".

i dont think blue light is actually that harmful but it mostly just messes with sleep

Graw-ton, not Grow-ton

I don't like blue LED's, they fuck with my depth perception. And LED headlights REALLY grind my goat. LED's above you is one thing, but when they're at you at a buck ten, FUCK YOU!!!

well i can refute it that way. make it about choice and statistics. the *"decrease"* of accidents in the night is *dismal* to a *FEW* compared to the circadian "damage" done to *EVERYONE* including the enviroment(bugs plants etc.( i cant believe i said that XD)) so we should stick to *HPS* or at the very *least* amber *LEDs* but not this *blue light madness*. PS. included in that damage is a probable change of more cancer due to melatonin disruption especially if you weigh that against a way better solution to prevent nightime accidents *having signal lights on you* instead of using as much light as possible for your view. because the biggest contrast is not seing something fullylit *but seeing a light in the dark*against a way better solution to prevent nightime accidents *having signal lights on you* like cars instead of using as much light as possible for your view. because the biggest contrast is not seing something fully lit *but seeing a light in the dark*

This video is like a preview of modern light technology damn good

I personally like the LED lights for street lights. My issue is their usage in automatic motion activated lights outside. I have nearly been blinded by specific houses anytime I walked by them on the sidewalk. Also their usage on headlights. They are so bright it creates a hazard. I have heard some people say, "don't care I can see better so I'm safer." The thing is if I don't notice that I am drifting lanes because of it. You may have just caused a head on collision.

Is circadian rythm disruption really an issue. It would reduce driver fatigue wouldn't it?

Far too technical! Have you ever bought a Sodium lamp they are very expensive!

How about cooler lights on highways and commercial districts and then warmer lights in residential areas and wildlife reserves?

Whatever.. Just put any light it is still better than no light

I don't know if this is a bad idea or dumb, but what if special street lights can be made that have programmable visibility, like what the 3M traffic lights did, to install in places close to homes and wildlife? This way, the installer can "program" the light output by putting masking tape on a optical limiter so then this way it will only shine and be visible on the street while from the houses the light source will not be visible even though the lens is visible.

What a nerd,, who cares

Things worth mentioning: Firstly, any choices we make can have nuance. For example, cooler lights on motorways (erm... highways? I think that's the american translation), and warmer lights in residental areas. A cooler less calming light is probably an advantage for alertness as well as visibility, which is handy for things like stopping time, and longer night time drives are already keeping people awake. Admittedly, as mentioned, street lighting is particularly useful when pedestrians are about, which tends to be residental areas, but the point is still valid, that's just another decision to make and a potential solution. A single standard isn't actually an advantage here. Secondly, it's worth also looking at car headlamps here. One thing I noticed when whiter LED lamps were first installed in my area is that they're pretty much the same colour as car headlamps. This can mean that distance street lamps can sometimes momentarilly be mistaken for cars, and worse... vice versa. While the lack of movement in the lights does give it away, it can still slow down reactions, which is always worth considering when high speeds are involved. Perhaps having headlamps and street lamps as distinct shades could still allow you to keep the benefit of quicker recognition alongside the cooler lights.

I hate driving down that part of 88. Actually I hate 88 period. I try to not go farther then 59

I enjoy your videos, I am too dense to understand what you are saying most of the time but you are touching on subjects that I am interested in and I thought no one else thought about. Like the street lights being changed over but here you are, talking about it and I too am on the fence on the change. Also, I am able to watch your “long” videos because your very dry sense of humor is awesome.

You fail to clearly explain what melanopic light and scotopic and which one effect the most our melatonin. But since leds give more blue light wouldn't it mean leds would be better at keeping people awake at night on the road?

nice notes about light pollution

Can cities in the future ever be light pollution free or neutral?

Blue headlights often hurt my eyes to the point of forcing me to blink so that's not a better alternative in my opinion as I cannot see past them, this is why I hate led headlights

We have LED Lamps too but the design is bad so the new LED Lamps shine into the Driver eyes and make driving harder then the old HPS Lamps. And the Light is darker with wet Street the Asphalt ist black !

make it about choice and statistics. the *"decrease"* of accidents in the night is *dismal* to a *FEW* compared to the circadian "damage" done to *EVERYONE* including the enviroment(bugs plants etc.( i cant believe i said that XD)) so we should stick to *HPS* or at the very *least* amber *LEDs* but not this *blue light madness*. PS. included in that damage is a probable change of more cancer due to melatonin disruption especially if you weigh that against a way better solution to prevent nightime accidents *having signal lights on you* instead of using as much light as possible for your view. because the biggest contrast is not seing something fullylit *but seeing a light in the dark*against a way better solution to prevent nightime accidents *having signal lights on you* like cars instead of using as much light as possible for your view. because the biggest contrast is not seing something fully lit *but seeing a light in the dark*

hey bro, you're a boss. we could use some realness in the "tech youtube channel" area. i know its pathetic but personally for me as an actual real world I.T. consultant who certainly will never ever be in front of a camera, critical thinking presented in your unique delivery that i can get down with while i smoke weed after 12 hours of being yelled at by people who make way more than me yet cant send a fucjing email or remeber a password, is in fact of high value to us both. consider feeding the algorithm. mac, apple, linux, chrome, google, pixel a.i. machine learning, big fucking gay data, trump, skynet / get fucked mate/ >_ $$$

Years ago I dreamt about those not-so-white LEDs that were in fact 2 narrow wavelenghths combined. If the streets were lighted this way worldwide, this would be filterable for astronomy. I live in France near Nice, Monaco, Cannes : the sky at nigth is a mess, even miles and miles away in the mountains, cities always glow up to very high ascension. So you have only small parts of the sky that is okay-ish.

I just like the look of orange lights more.

i like white light better.

Here in New Zealand, our traffic lights are already all LED, and our street lights are already half LEDs, with the rest of them being slowly phased in as the old ones die out.

Do soft white or bright white led bulbs have the same effect of the high pressure sodium bulbs vs daylights bulbs that produce a blue light? I am a past electrician and current undergrad ( industrial electrical / home depot electrical department employee).

5:20 I knew those streets looked familiar, that is fairly close to Chicago

Damm, another Chicagoan? I recognize pace buses anywhere

As an electrician, most LED bulbs will say to disconnect the ballast or not. In general, a replacement LED bulb is used with a ballast bypassed, i.e. 120/240v direct. True LEDs have a driver to give them the exact amount of volt/amps. The replacement lamps must have something in them that's doing the same thing, but hardly with the same efficiency that a planned LED install with a proper driver has.

I just uploaded a video comparing an LED and Incandescent bulb side by side and go through the costs to run per year.

You're right that low pressure sodium is definitely better for astronomy which is why it's used near professional observatories but high pressure isn't bad either. For amateur astronomers, high pressure sodium is absolutely preferable to LED because although we can't filter out all of the light pollution from HPS street lights we can filter out most of it. With LED streetlights now, we can't filter any of it. My city (Ottawa) has switched over to LED streetlights and it's now useless trying to look at the sky anywhere near the city. When we still had HPS lights a couple of years ago it wasn't amazing but it was workable with filters. The astronomical filters for LPS were able to get most of the light pollution. Now that the streetlights are white there's no chance. It's like having a full moon every night. And the city didn't cheap out either, they replaced all of the fixtures with new ones that have much better cutoffs. The problem is light scattering. One thing that wasn't mentioned in the video is how much easier it is for bluer light to scatter. Not only does this contribute to city glow but it also has safety concerns here in Ottawa, especially in the the winter. The orange light from HPS lights did not scatter nearly as much in the snow as the new bluer LED lights. One of our major arteries was halfway through the transition last year and I happened to drive on it during a snow storm. In the HPS section visibility was fine, it didn't seem to be snowing that much but as soon as I transitioned into the new LED zone I found I was unable to see very far at all because of the glare. The light was bluer and was making it far more difficult to see down the road, even though the rate of snow was unchanged. As soon as I transitioned back to a part with the HPS lights visibility was fine again.

Americans call the police because they are scared of the Milky Way? Perhaps the world community should reconsider allowing them to have nuclear bombs...

If you think I-88 is lit great you should try I-90 from Elgin to Rockford. Those led lights make it look as close to daylight as I’ve seen at night.

I'm having a nostalga attack. Why are all the clips around the DuPage area where I used to live?

Random fact:. They moved to blue lights on the Tokyo underground and suicides decreased dramatically. No one is sure why

Why do green traffic lights always look blue on camera?

What a brilliant and informative video! Thank you for making it.

Illuminate your mind with Technology Connections! :-D

I think the blinding tendency on foggy conditions, or when snowing, has to be taken into account. Warm light is a lot better under those conditions.

One important issue to be considered is how the various colors affect our night vision. When we go from an illuminated street to a dark street there will be an adjustment time that could be an accident waiting to occur. Not scientific but I feel that there is more of a reaction time to the "blue" headlights than to the traditional incandescent headlights, although that may be more a brightness issue than a color issue. I have wondered also why they don't mix in some other colored LEDs in these fixtures to get a flatter spectrum.

Some of those "blue" lights on some cars hurt my eyes at night.

I‘ve never seen a fully lit Highway (i‘m from germany) but here in Germany the Autobahn‘s/ highways don‘t have any lights. I don‘t really understand why it‘s necessary anyways to light up the Highway especially at the low speeds you are allowed to drive in the us.

HPS lamps also take couple of minutes, give or take, to reach their full luminence whereas LEDs illuminate immediately. Thus LEDs could be motion activated on roads which receive lesser usage to reduce power usage and light pollution. Motion sensors could be placed before the intented part of the road to be lit so the driver’s wouldn’t be surprised by the sudden blinding light

The largest problem with "White LEDs" is that they're actually *Blue* LEDs with a yellow covering - which means they still have a peak blue emission present. And the wavelength it's producing ? Well, safe to say, astronomers aren't very happy with it. I'd agree though that a somewhat yellow-ish LED might be the best truce possible.

7:50 Stop driving on the left...

Epic comment @ 8m24s!!!

I guess it’s good in rural areas but bad near residential buildings.

Moonlight has a relative melanopic content of 4.56, so how can any rmc below that be circadian rhythm disruptive?

Being scared of the milky way is just a sign of bad education...

I find it hard to drive in the fog or when raining with white/bluish LED street light compared to traditional amber-ish/yellow-ish light. Anybody find the same?

Was the speed limit really 56mph??

A lot said with very little information provided about the subject and only whined about trivial things.

Can someone please explain the negative effects of light pollution. He didn't seem to say why this was such a bad thing.

Excellent video! Should be required reading for all street and highway departments. Aesthetically, I prefer a light that is bluer than HPS. When I was a kid, mercury vapor lamps were everywhere, and I hated the "new orange lights" that replaced them.

Who is going to clean up the mess in my house created by this video making my head explode? I have never been accused of being the brightest bulb on the chandelier, but I am somewhat of a flashlight freak (especially during hurricane season) and LEDs definitely are rocking that world.

You never mentioned, but I was told that the color range of the HPS goes through fog better and thus creating more visibility during Fog and perhaps rain. At other times and conditions, the LED should provide much greater visibility.

I've heard that low pressure sodium is better in the rain/fog because it doesn't tend to scatter. So there's that. It'd definitely be nice if street lamps would dim after a certain point. It'd be nice to see some more stars in my backyard. I have a few stupid streetlights right around me. One of them is burned out and I don't plan on calling it in.

Disruption to the Circadian Cycle is highly misunderstood. You want night drivers to be alert and aware of their surroundings, not sleepy and unresponsive, so LED lights that might have more Blue spectral content is actually safer became the drivers are alert and not sleep. Since LEDs are more efficient, the amount of blue light really isn't all that mush (despite the lights looking more blue than sodium vapor) that is because sodium vapor require the use of a much brighter bulb which puts out that same amount of blue as LED and a lot more yellow. This is seemingly counterintuitive but think it through, it really does make sense. I recall back when sodium vapor was deployed in my area and I note that it was more difficult to see other traffic than the old bulbs. Everyone else just kept repeating that they were "new" so they had to be somehow better. I'm thrilled to see that someone has finally put together and explanation that vindicates me! I'mm looking forward to having my community switch over to low powerLED, of the correct color spectrum, using the correct downward-directing lenses, in my area. Thanks for the great video.

The roadway spotting artefacts you described are a result of the retrofitting of LED lamps to existing lampposts. In future new construction projects lamps could be placed closer together and much lower to the ground.

I was listening while working so I might have merely missed it but it seems like you did not explain what the circadian rhythm is... (Yes I guessed it and then googled it.)

Bring back mercury vapor lights, those look the best!

I find it hard to see with any street lights as my eyes can't adjust to being sensitive enough so, this is especially true with the white/bluish LEDs. I live out in the country and when I drive at night, I can see 3-4 times as far and much wider to the sides when its totally dark and just my headlight. Go to the city and I find it hard to see because of the light being localized and not being able to see out to the shadow and unlit areas, even with my headlights. I like the sodium lights better as it allows my eyes to get more sensitive to the dark compared to cooler LED light. As for the light pollution, it has greatly increased due to the bluer light, it travels at lot further out to the country now, where sodium only few years ago was just a patch of orange glow on the horizon, now its more like a late twilight entire sky glow.

I reckon that moths and other nocturnal bugs would get attracted to the white / blue glow of LED's moreso than that of the bulb.

I agreed with the directional correction idea. Block, partially or fully, the light angled off-road toward houses/buildings. Just angle it down and away.

wow i was just about to comment this

Terrific video! I don't know how I stumbled upon it while watching political news videos, but, I'm glad I did because you managed to quickly explain a lot about a technical subject in a clear manner without resorting to demeaning simplistic analogies. One area that wasn't quite clear to me was the effect that the high temperature light from LEDs has on the circadian cycle (i.e. does it lull you to sleep or does it keep you awake)?

Why are there lamps on the highway but not on the city road?

You kinda overlooked the real major reason that streetlights became a thing. To combat night-time muggings and murders in London.

Energy use and safety trumps circadian rythm and esthetics any time. And you only need to change it once per decade. Not to mention, there are probably as many people if not more that work night and afternoon shifts, so for them, the blue light could help staying awake while driving, and to get used to the night shift faster, hence better daytime sleep and safer driving.


I always preferred the blue/white light. I remember when I was a child proclaiming such, as not only was blue my professed favorite color, but you can just see better with the blue/white lights. The orange ones make everything orange and it feels like you lose detail. As this video shows, science vindicates my observances in this regard.

Couldn't a slight tint be added to HPS so that it better matches with our scotopic light sensitivity?

I find the sodium lights are excellent in the fog. Here where we have LED's they still have the Sodium lights around the bridges. .

It sounds like part of the problem is greater lumen output which is a different issue than LED vs Sodium. They could make dimmer LED's that consumed even less power.

What’s not to like about the aesthetic of a 5000k led? It looks way better than the ugly shite yellow tint of a 3000k led. And the circadian rhythm concerns is just bogus if you ask me. It’s just looking for cons for the sake of looking for cons. And better housing will reduce sky glow. I’ve never seen the aesthetic appeal of a warmer light. The bluer light actually is closer to the natural moonlight our eyes have evolved with, I think it’s more aesthetically pleasing that way.

I’m pretty sure if I’m driving I’d rather have the lights prevent me from sleeping. If the concern is for non drivers, then blackout curtains can be as cheap as $10.

The city of San Jose nearby where I live is just below the Lick observatory, and so all of the street lighting is yellow Low-Pressure Sodium. In my home town, a lot of the street lamps are being replaced with white LEDs, but I don't really like them because of their harsh glare.

I can remember, as a kid in the 1980's flying over Los Angeles at night in a Cessna, at 4000 to 5000 AGL and having enough light reflecting off the wings that you could read inside the airplane. I always wondered why they were so keen to light up the sky.

I think its not so much the "blue" color of LEDs destroying vision as much as it is having such a bright light source within 2 feet or less of our eyes for extended periods of time. I always thought it was funny as a kid to shine a flashlight in someones eyes as a joke, but also having been on the recieving end of it I realized that holding that light on someones eyes for more than a second was not good. But Im no expert.

Can't filters be used to change the color? Or is that less efficient?

less efficient. It's the same as putting multiple layers of clear plastics on top of each other, in the end you barely see through.

You kind of want to disrupt circadian rhythm on the road anyways.

My city has been installing some LED's :-)

I can imagine your tinder dates

One of the major advantages we get with LED lighting fixtures is that we can turn them on and off, dim them, and even change their color to a certain degree. So we could utilize a low output, warm color when no traffic is present on a roadway, and when a vehicle approaches the color could be changed to a higher temperature light for best visibility. That way, a driver always sees in the best light, but people living in neighborhoods surrounded by streetlights wouldn't have to suffer the sleep deprivation of having harsh blueish light outside all night long.

A gay street lamp expert. Cool. But why is this shit being recommended to me?

Youtube, that's why.

Not even gonna watch the video. Without a doubt LEDs should replace HpNa bulbs. LEDs dont need bulbs changed. The only changing your doing is the whole head with the lights and odds are the ballast will shit out before the lights. 2 LEDs are a fuckton cheaper to run than standard bulbs and 3 LEDs are far brighter HpNa bulbs

Also LEDs are a lot easier to wire and because HpNa bulbs get hot the poles at times have to be extremely high up. LEDs dont heat up like that so you can have just a 15 ft tall pole light, sometimes even as small as 12ft depending on where

Personally, I prefer daylight white LEDs (5000-6000k). It's like a having a miniature sunbeam, no color distortion, and just more natural to the eye. To my mind, the goal of lighting should be to aim for simulated daylight, as if you've just ripped off the roof and let the sun shine in. ;)

One problem is shitty luminaires... there are many LED streetlamp replacements from my local authority (Salford City Council, UK) that turn on and off repeatedly for the first five or ten minutes, and multiple heads have flickering/flashing issues all night, and some crappy replacement heads shine excessively bright light out of the sides that obscures vision. I am not against new technology, in fact, all my bulbs are LED at home... but I am against crappy implementation without proper research and consideration. I also don't know what the impact on local wildlife is considering its circadian rhythm. It is especially concerning near woodland areas or parks for wildlife. Never mind the bright white light that intrudes into homes with crappy LED luminaires.

Yeah, my college dorms have terrible LED super bright parking lot lights. They put normal pull up blinds in instead of blackout curtains so it's like a ufo is flying outside your window.

Just wanted to add the effect on night vision recovery... due to the fact that (from Wikipedia) "Retinal undergoes an irreversible change in shape when it absorbs light; this change causes an alteration in the shape of the protein which surrounds the retinal, and that alteration then induces the physiological process which results in vision. The retinal must diffuse from the vision cell, out of the eye, and circulate via the blood to the liver where it is regenerated. In bright light conditions, most of the retinal is not in the photoreceptors, but is outside of the eye. It takes about 45 minutes of dark for all of the photoreceptor proteins to be recharged with active retinal" rod cells are both very sensitive in low light conditions very nearly insensitive to red, so using light that predominantly only activates cone cells leads to faster recovery of night vision. Something you've probably experienced if you've ever been on a long drive on an unlit road and passed through a section with lighting (or had someone pass you with those blinding blue headlights!) Although not a large factor if you are only driving in areas with street lighting, it is still something which should be considered in more rural areas.

I like the look of white LEDs. Feels like the future, man.

False, we see white/blue light better than the yellow BUT white/blue light is worse at differentiating objects. Led look bright but watch a dear on the side of the road with even dimmer yellow it’s more visible and more important the human eye pays greater attention to the yellow light. I love and have led flashlights, there super bright and batteries last very long but try doing detailed work or Reading engine numbers and use a incandescent and see how much easier it is not only to read or see detail but seems to not effect attention

Where I live they used to put purple lights in small public areas so drug addicts wouldn't be able to find their vanes.

Just use 4000k light temperature led. Problem solved right?

I love sodium lights , they have 1980s -1990s driving vibe

Technology Connections We could compromise and use LED lights in downtown areas and highways, where driving safety is more important, and use HPS lights in low traffic and residential areas, where collisions are more rare to begin with.

why not bright LEDS near highways, and increasingly amber lights near housing?

I like the new LED lighting we are using here now. The color temperature is well matched with the moons output, so if the light shins through your windows, it's easy for your body to interpret as moon light.

Led headlights fucking blind me tho

I actually greatly prefer cooler temperature (5700-6500k, "daylight") lights in general, even in my home. I'm often frustrated by stores with sales on LEDs but that only stock 3000k/soft white bulbs. I'd be interested to see some sort of poll on people's light temperature preferences. From what I've read I seem to be "the odd one out" but not alone. I guess what really matters is that my wife agrees and bulb choices in our house are easy :-P

I like LEDs.

My local municipality has converted completely to blue LED street lighting, and I notice less sky glow than before. In fact, it's easy to see light from other municipalities bleed into our sky, while the reverse is much less noticiable.

I would assume less sky glow would be from better designed fixtures that produce less upward glare.

Is this why blue and white lights are so much more annoyingly bright?

I think one good option would be a mixture of color temperatures. In residential areas, like neighborhoods and apartment complexes, lower temperature or dynamic light fixtures could be used to avoid disturbing the circadian rhythms of people in the places where they actually sleep. For non-residential areas, like commercial districts and highways, higher temperature lights could be used as the benefits in efficiency and safety might outweigh the disruptions in circadian rhythms. The disruption might even be beneficial as reducing melatonin outputs in drivers on long trips means fewer people falling asleep at the wheel and therefore a much safer environment.

8:28 What were the police supposed to do? Shoot it?

Its a little long for me to watch all of it right now, so maybe you answered this. I feel like I can see more when an area is lit with HPS or lower color temp, then with LED or higher color temp. In other words, I fell like it takes less low color temp light for me to adequately distinguish objects and driver or pedestrian safety risks, then with high color temp light. I feel high color temp light has to be way brighter for me to feel like I can see as much as with low color temp. And I'm not sure at all about this, but I feel it is because of depth perception. Low color temp light gives me way more depth perception, which is high on my list of priorities for "adequate" light. That's what I feel anyway. I wonder if there is any scientific basis for if different color light is better or worse for different aspects of vision, and what aspects of vision are more or less important for certain tasks, such as driving?

Over here in the Netherlands we've done a lot of research in night lighting thanks to the big light company called Philips. The answer indeed is complicated. Rijkwaterstaat for example developed the bat lamp to make sure they won't intterupt the bats as much. However, this light is oretty inefficient. Green light is the most efficient form of lighting. On the island of Ameland they use green-blue lighting to save energy. On the road there is also green-red street lighting (4 green LEDs, 1 red LED) to save energy. The red LED will make sure we can see the colours of traffic signs. However, these green lights are disrupting nightlife except for birds that are flying at night. White light is the best compromise despite its many disadvantages.

«…cool colour temperature is harsh and aesthetically displeasing….» Relative terms. I am from the tropics, and the"warm, pleasing glow” of incandescent & other warm temperature lights is very displeasing to me. As a photographer, I could never understand why continental American photographers insisted on using a warming filter (with film) or a warm tone on portraits to make them “more pleasing.” To me, it made them look unnatural and displeasing. The further away from the equator one is, the lower in the sky the sun often is, and for longer periods in the summer, producing a warmer colour. In the winter, sunlight is rare, and artificial lighting, usually warm, has been the norm. All of this contributes to non-tropical dwellers finding “cooler” temperature lights harsh, —only really seen at noon-ish hours— and displeasing —rarely ever seen— where us tropical dwellers see this “cooler” light as normal, and pleasing, as we are mostly surrounded by it during our wake period, whether summer or winter. I also wonder whether this, “affect circadian rhythm,” thing is also location specific, as after the warm sunset, we tropical dwellers are met by the “blue hour” followed by the mostly blue night sky (save for light pollution by the harsh, aesthetically unpleasant, warm artificial lights we import from North America).

Never seen a photographer using a warm filter. Kodak was always warmer than Fuji.

We recently got some of those fancy smart LEDs in our residential areas. They can dimm and change their colour temperature which is really nice. They also communicate with each other wirelessly. What they then do is dimm down and reduce their colour temperature when no car is coming and as soon as they detect a car they tell it to the ones in front of the car and illuminate fully and some lights after the car they slowly dimm down again. These things are just amazing!

I only buy Cree led. They're the best in the game. In architecture, we spec to Cree led more and more

The problem with the Led street lighting in my town is: 1. your eyes can't adjust to and from it. Simply put, it temporarily blinds you. It is bad for night vision because your eyes can't readjust to the dark. Amber color lights are much better at preserving night vision. 2. They are bright. even out of the corner of your eye, the light source is painfully bright, I have to look away from them just the keep them out of my peripheral vision. 3. Led street lights light up a small spot on the road, not the wide field of light that the sodium bulbs give out. The ones in my town literally light up a 15 foot diameter spot on the road. 4. The higher color temperatures produce a glare. You literally cannot see what's on the other side of the light. There is too much contrast between their light and the darkness. It's like they produce this tube of light that you can't see past, or out of. 5. in the rain, they light up the rain drops on your windshield a lot more than the sodium lights do, producing glare.

I think you repeat too much the same thing...

the dangers of cool white leds

Agreed! The LEDs produce way too much glare in fog

Well my eyes went to the toilet with the help of two big monitors. Now wearing yellow Gunnar glasses and my eyes have recovered pretty fast. However, I've always been sensitive to blue headlights and now I'm even more. Don't underestimate the power of blue light. My vision was blurry not unlike snow blindness. I felt burnt.

Where I live most lights are already LEDs. Lights in neighborhoods are still sodium though.

wa wa wait. are you really saying those blue supernova level headlights i see more and more aren't only legal but even BETTER? has this paper been confirmed by more sources? i'm mounting some 1kw blinking lamp racks on the back to deter dem suvs from pointing their lights at my mirrors so i'm looking for the best way to blind them back. thanks! :)

My grandma had a sofa made with the same fabric as that jacket. I swear it's the exact same.

Great video. I think you are in the minority on the light temp, at least on the road. Just look at the headlights both from newer cars and retro-fit HIDs. I love the 5k to 6.5k temp look and know the visibility is better. Just about everyone I know likes the same.

If you were to use RGB LEDs near observatories you could filter out the three wavelengths if you wanted to, more easily than the broader spectrum of a real white LED.

i never thought about how passionate people could be about street lights until now

I'm in favor of HSL in quiet residential and LED in all higher traffic areas.

I mean, they could still use a 5700K LED and put an orange-ish filter over the lights to achieve the same result as using a lower one and it still be as efficient as the harsh bright white light that hurts to look at, right?

I'm surprised you didn't mention anything about how Trucks and SUV's with the bright blue lights are blinding when your eyes are adjusted to darkness. Having one drive up behind or next to me at night is one of the worst things I have to deal with every night

Just recently found your videos. EE for a municipal utility. Most cities, including ours have standardized on 4000K lighting color for LEDs. It is about a 45% savings on energy over our old HPS lights, is the same color temperature as moonlight, and is not as hard on circadian rhythms. The biggest savings with LED street lighting, is seen from fewer trips to service the lights. They last longer, and have basically eliminated our need to send out big gas using trucks daily on street light repairs. They also weigh a lot less than Mercury vapor lights which were really hard on the arms and poles and had more trouble during wind storms. When we did our city wide change out it was only 2 years to pay back the investment, and as mentioned before our calls to handle non working streetlights have nearly been eliminated. We have had some kids get cute with BB guns, but the fixtures have been incredibly reliable.

As someone who drives a lot in many areas of the country I can tell you without a doubt how much relief I feel when I get into an area that is light with the blueish LED lights. I see much better, my eye strain drops within seconds and I want people on the road to be awake at night. I don't care about disrupting their sleep, in fact if they are on the road driving a vehicle, they need to be disrupted to help keep them awake. Coupled with energy savings it's a no brainer.

@FutureHindsight , they were often part and parcel with UV filters. One could get a regular UV filter, or a “warming UV” filter. The latter had a warming effect on skin tones, outside of the removal of the UV effect. It was a pale pink colour. I never used it. Back then, I did mostly B&W film, and would always use a UV filter to darken —or more accurately, less brighten— the sky, but would often add either a polariser, and/or or a red|orange|yellow filter to really darken|darken|slightly darken the blue sky, making the white clouds stand out. When I did colour film, no colour filters. Yes, I found Kodak Gold gave warmer tones than Fuji or AGFA, and therefore would rarely use Kodak. I found the colour unnatural.

Japan spent millions to switch to led and then millions more to switch back because of eye strain on the population. Just a random fact rolling through a sea of comments.


I'm pretty sure most of us can do Without Blue headlights. I wish they would clamp down on this. It's just messing up the vision of the on coming traffic.

Thing is those LEDS when used as headlights BLIND THE SHIT out of everyone else. Sure you can see better and more clear but my lord, especially when they're behind you

well i can only speak for myself. im not often driving with a car however when we go on vacation i love the relaxed yellow lights in the night on the autobahn :3 there is just some special with amber colours that makes them look so cozy. what about using amber coloured leds on long straights and blue coloured leds in intersections. it wouldnt stress people and it would also warn them when they really have to pay attention. >^-^

One of the big problems you didn't mention with LEDs is the heat. With HPS heat is good and the system will run hot because the sodium need to be a vapour. With LED they still produce heat but high heat will significantly damage them and shorten the lifespan. This means swapping between them requires a complete replacement of the head and attention paid to heat dissipation.

7:05 "...cooler temperature of many LED replacements is harsh and aesthetically displeasing..." ... I dont know man, I like those much more.

Well, in Hungary there's been a political scandal recently, related to LED street lights. The new lights have such a tight, tiny "spread", that you can't see nothing unless you stand right below them on the street. I concur that some cities look horribly dark at night since they changed the lightning. There were even deadly accidents blamed on the change. Is this business as usual with LED lights, or have our politicians made some blatant nepotism worse by adding technical incompetence as well?

A few years ago my city started replacing the HPS lighting with LEDs. I first noticed it outside my parents' house. The new light is flat on top and is mounted so it is about parallel to the ground. I noticed the improved visibility first then looked up to see why. I also noticed that there seems to be much less light pointing upwards than before. I can barely see the trees/poles/wires above the lights compared from before, even when blocking the light fixture with my hand. I wonder if this was taken into account when determining the apparent increase in sky glow from LED lighting. If less light is being emitted upwards such that the majority of light that reaches the sky is reflected from the ground would that not also lower the amount of sky glow? Does the amount of human perceived sky glow rely more on the colour of the lighting (and perhaps the colour of the reflected light since pavement reflects not only more light than grass but also a different colour since street lights are usually directed at pavement not grass) or on how much light is reflected off the ground below these lights?

HPS lights mimic the suns corona, this has an effect on the subconscious mind, better for crime prevention. LED does nothing.

RGB street lights when

For some reason, I only recently came across your channel, and even randomly choosing videos on YouTube have now viewed several and subscribed. I liked this one a lot. I've always gone for low energy lighting (I was using some CFLs over 30 years ago for economy and lack of frequent replacement) and am now about 50%+ converted to LED bulbs in my home over those previous CFLs and a few Halogens (Xenon filled seemed most efficient). I hadn't previously known of the effect of colour temp during bright and dark periods of the day and found that most 'illuminating' ! In the part of my kitchen that I use for food preparation I deliberately chose about 4500K LEDs and I like their seemingly brighter effect. Elsewhere they're mostly 3000K. 2700K just seems a bit 'gloomy' for my liking.

Motherfukers change to white leds in my street.. Now it's like someone is doing a autopsy

Wouldn't a higher melanopic content be good for highway lighting, since it would theoretically keep people awake? So then.. there's really no negative at all to switching to LEDs, at least not on highways.

That speed limit sign was for 56mph... I’ve never seen that before

To me the problem with LEDs is that they are so bright that I have to lower the sun visor at night to avoid looking directly at the light sources. Of course I have to look at the road, but It affects my preipheral.

Erm no. Street lights are LOW pressure sodium vapour lamps, with a characteristic luminous wavelength of 589nm. High pressure sodium lamps have a far wider spectrum which is a far closer approximation of daylight (though not really that close) and are far less efficient than low pressure sodium. Even wiki get's that right.

i remeber when we got yellow sodium lights in place of the old bluey white mercury in about 1970 in my village, was like vegas! I dont care what science says about them being poor, they were dazzling in comparison. also there very efficient, white led isnt that much different, and yellow sodium didnt cause light pollution for stargazing as you could use filters that filtered just the sodium light, you cant do that with leds... and lets face it cars have headlights, and most of our roads are unlit where i am. leds have a purpose, and many uses, but i'd sooner have the old yellow sodium lights.

The 120Hz flicker of LED lighting, particularly when driving, makes me sick to my stomach.

I'd just say, use 3200K (tungsten-balanced) LEDs in residential settings (streets, houses, etc), offices and restaurants, and then use 5600K (daylight-balanced) LEDs in city streets, parking lots, industrial enviroments, etc. I think stores are one thing that could be debatable though. Another thing could be using daylight calibrated lights during the day and tungsten calibrated lights during the night, but that's more a subject for indoors lighting than outdoor lighting. Worse than either of these two is using a mix of the two in the same location, because you basically have the disadvantages of both temperatures.

Enjoyed the video. I'm the opposite-I actually prefer the color spectrum of the newer LED Street Lamps ( weather 3,000k or even 4,000k is MUCH preferable to the horribly ugly HPS color output. ) I'll take the risk of inpact to my circadian rhythms. The WORST color was the old LPS lamps installed in the city I grew up in in the 90's they were actually depressing.

Isn't it interesting that blue light filters can improve sleep schedule? Blue light at night keeps you awake, but orange light helps you sleep. Blue light is night away from camp under the moon, and orange light is relative safety of the campfire...

What is it about metal halide lighting that makes them maintenance intensive? Do the fail frequently? If so, is this something that could be improved upon?

This is so informative. I love statistics and you present them in a very concise and easy to understand format. Bravo sir! +1 subscriber

Now I know why its so hard for me to get a good nap in while driving on the freeway.... its those damn LEDs

Mercury vapor is the future. At peak performance they produce an amazing blue+UVC light, which you sadly need quartz glass to let it escape. Both, blue and UVC, are easily scattered, unlike redder colors they wouldn't reach as far and pollute the sky, that's why the police uses blue, because in war you don't want to be seen from above. Just joking around, but the blue is really pretty, y'all should check it out.

I'm not sure that using a light fixture that helps us fall asleep (while driving) better is a worthwhile pursuit. Better to upset the cicadas a bit and arrive home in one piece.

My city has been replacing all the light fixtures with LED, not just the bulbs, but the whole fixtures and they're much improved, however, the one they replaced right in front of my house has a very wide angle and shines on the houses and seems brighter than the old bulb, annoying at night when it shines on the windows...

It's interesting that moon light is blue but blue light disrupt circadian cycles. I would expect natural phenomenon like moon light would not shape evolution to distract sleeping by it. Perhaps there is some fine nuance in the intensity or the specific blue wavelenght to it, and that would not cause disruption, same as moon light does not do?

Every major city should have led streetlights by now, we have the technology :) but then again it's expensive to replace all the current fixtures

High Pressure Sodium make roads more visible in the fog/snow conditions

We should also consider the impact of disrupted circadian rhythms on driver fatigue. As driving fatigued can be worse than driving twice over the (UK) alcohol limit, if people's sleep is indeed disrupted enough by cold lighting road safety could be compromised day and night.

It seems like circadian rhythm disruption in this case would be a good thing, since it will help prevent people from dozing off behind the wheel.

Totally unrelated to the video, but it's pretty cool that we're pretty much neighbors. lol. Although, I'm much closer to Chicago and the 290.

I prefer white light over warm light

Nick Booker Disrupting circadian rhythms != making people tired. In fact, it CAN mean the opposite. Blue light is supposed to contribute to insomnia. Thus, I think, if anything, it would make you MORE awake. If you're driving at night, you're going to have problems with fatigue the next day anyway. Blue light might actually make driver's stay awake while they're driving at night.

You didn't comment on their usability and comparison in fog conditions. Our elementary school books mentioned that sodium lamps light have better visibility in fog conditions. But LED lights weren't in as an option at that time. How do LED lights fare during fog conditions when compared to sodium light.

Wait a FLIPPIN MOMENT... The lights affected the direction that the newborn turtles would go... But you call it's effect on humans "questionable" or "fear mongering"?

0:40 holy crap that intersection in the video is less than a mile from my house :0

very well researched video !

People who use led are dicks, it's like having them bright you.

The other thing I can think of is car headlights are generally whiter than street lights so people don't mistaken street lights as vehicle lights. I remember driving on this road where someone had very white lights for driveway lights and I thought it was a vehicle coming the other way.

Are there any studies that look at "night blindness" when moving from a well (blue/white) lit area into dark area and how it compares to reddish light? From my own experience I'd say that eyes need a lot longer to adjust to darkness when adjusting from white light to dark. In the area where I live, there are unlit pathways with a couple of white street lamps around the houses. These basically blind you everywhere in the area and except right below them, where they light up the street in front of the houses. In those areas it's quite common for pedestrians to trip over roots, or walk into little ditches and from a personal feeling I'd say, those white lamps make the whole area less safe.

I don't want to sleep as much when the road is light by LED, though aesthetically i do prefer HPS

I am not a fan of the LED technology, I like the old lights better. The biggest one for me isn't colour, but OUTPUT! With the new LED streetlamps, streets are darker and don't feel as safe. It looks ugly, and cold. My mom often commented about that when walking home at night. My bedroom used to be lit by the streetlight at night, and since my city replaced them with LED a few months ago, the light coming in my room is barely a night light. Same with Christmas lights....they lack that magical 'glow' they once had. And I also sell headlight bulbs at work, and I'm finding that the white/blue lights need more output in order to actually see enough detail out the front.

Light pollution is the cause of fireflies in danger of becoming extinct.

Well, if you are driving on highway, you don't really want lights that'll help you sleep. Those can be put in neighborhood.

One thing I'll say about the circadian disruption caused by blue street lights is this: It's both a blessing and a curse. Yes, it can mess up how you sleep. That kinda sucks. But... That can actually be useful for safety late at night. If you're driving around at, say, 2 in the morning, you're probably gonna be pretty tired. Warm yellow light, similar to a sunset as you described, it certainly isn't gonna help with that. But the blue light can keep you awake longer, which is good if you're quite a way from your destination. Having a harder time falling asleep later is a worthy tradeoff for being less likely to fall asleep at the wheel IMO.

i dont mind disrupting a persons sleep cycle if they need to be awake to drive at the night

We still have these old fixtures

Mr. Connections, I'm watching your entire back catalog at this point. Thanks for what you do. I'm learning about everything I didn't know I wanted to learn more about. Expect to see me on Patreon.

And you cite your sources in the description box down below. I'm going to Patreon right now.

In this case, it'd probably be best to use a monochromatic LED around the scotopic peak of 530 nm (around the frontier of green and cyan, if I'm not mistaken) which would be energy-efficient, melanopic for drivers on the road, and could be filtered from homes by using thin-film coatings on window panes engineered to reflect the specific wavelength, thus nullifying the melanopic effect inside homes.

So change em up every mile or so. Boom! Actually I think they do that on one of our newest freways.

let the free market decide ops only the government has roads

The lights in front of my house were replaced with LED from sodium last year. The difference is amazing! The sodium yellow seemed so dim.

LED headlights are blinding. They should be made illegal. I hate driving at night with people who use them. Oncoming traffic is so bright now, that you are often mistaken in thinking the car coming at you has their high beams on, when in fact they are just LED lamps. I have to almost constantly keep my eyes off the road, and on the shoulder, just to make out the lines on the pavement. This isn't safe, but the alternative is to not see anything except blinding light and an afterimage for a few nervous seconds after the asshole has passed. Driving a sedan with a pickup or SUV behind you that uses LEDs is similarly frustrating, as their lights line up with your mirrors, causing you to be blinded from behind. This is further compounded when the tailing vehicle drives too close. I find myself constantly pulling over so a jackass Ford pickup owner with a lift kit tailgating me with LEDs can go and crash into his scheduled tree at 3am without ruining my eyesight along the way to the scene of his death.

There’s yet another aspect. LEDs often have crappy diffusers, so you end up staring directly into the individual light-emitting elements. This makes it much more difficult to see the surroundings, leading to various complaints of “lots of light, but can’t see anything”. Then there’s a question of transitions between lit and unlit sections - LED completely ruin the night vision.

Wasn't there some studies that found that bluer streetlights seemed to reduce the incidence of crimes?

great video but why do you tend to repeat yourself so much - you could easily cut the video in half and i would think get many more viewers thanks for the great content

Just discovered your channel the other day - really enjoying your in-depth videos.

This is good, possibly important, information. (I am not a sponsor).

Red or yellow streetlights that don't interfere with sleep would be better for overall health. Then simply divering slower at night mitigate the lower visibility.

When it comes to aesthetics I am completely opposite of you. I hate orange light and love more white/blue light. I usually replace the lights in my house to be more white/blue just because I like it better.

Problem is: what happens when it illuminates things? The light reflects. Light pollution is already so severe that most people can't see the stars in the sky anymore, it's like they just disappeared. And around where I live(small city few thousand pop) the fireflies are not to be seen anymore even though 50 years ago they were everywhere, to find them you have to go miles from town now.

tyler higgins In the winter months when it's dark from about 4-5pm it mean most of my working hours are in pitch black driving down motorways at 56mph in a vehicle at potentially 44 tonnes of weight. Like it or not those streets lights are a safety boon, for a car driver who has a twenty minute commute when they finish work at 5pm I can see why they could think "why do highways need street lights" but for people who spend 9-10 hours a day driving those blue-white bright lights could be the difference between staying awake and getting home safely at the end of your shift and falling asleep and death. But I'm onboard with HPS lamps or even no to minimal street lighting in rural areas.

I sometimes feel like the only person on this planet who actually appreciates cold light over warm light. I am probably not the only person to think this way, but it baffles me everytime that someone could actually enjoy warm white light.

I changed my light to led it does not light up as much of my yard. Will a acrylic refractor help? The led light didn't come with one like my sodium did.

What I have always wondered is why the warm/cool description of light colors is bass ackward. Anyone with the slightest physics understanding knows that orange and dull red objects are cooler than blue ones(when the light is derived from their temperature.) Just try it, and ordinary filament lamp. Slowly increase the brightness(which corresponds to temperature) and you will see that the reddish/orange is at the COOLEST point. And it should be obvious because the lower color temperatures are warm while the higher color temperatures are cool. How moronic are we?

would i be able to see a bit better at night then if i wore blue tinted glasses?

Could you build a monochromatic led light?

"Moonlight and starlight are pretty bluish" Actually, no. The moon is gray; moonlight from your chart is actually only 4681k, or a very neutral white. Which is cooler than a yellow light, or than incandescent, but not as cool as a common high-output low-color-quality 6500k led, and besides, cool light is worse for glare - ever been blinded by bluish headlights? Stars are on average fairly similar to the sun as well; though I can't recall the exact average. Also: If 589nm were used at the same level of brightness as many LED systems are, it would be closer to the photopic range - these systems are blindingly bright. And when someone has been exposed to rather bright light... their rod cells will not recover very well at all. They'll be in photopic mode for much of their drive, if not all of it, depending on whether they can manage to only be exposed to dim light or if they will be repeatedly blinded by bright light and glare from signs on the side of the road, or oncoming headlights, or some of the existing LED lights. Oh, and as for light pollution, even apart from the ease of filtering 589nm light, there's some things the LEDs do that's an issue. First, even if they were flat on the bottom, the light coming out just slightly below sideways will end up hitting clouds a few miles away as the horizon drops underneath it and thus light the sky. also, the increased brightness typical of LED setups will mean that tons of light bounces directly off whatever they're aimed at and causes light pollution anyway. I suspect the bluer colors might, since they diffuse more in air and haze, be prone to lighting the sky while the warmer ones might mostly escape if they don't hit a cloud; at least, they'll do no worse than the existing sodium.

Be careful when comparing lighting efficiencies. Lumens are a scale that's weighted according to the sensitivity of human eyes. This is why 550nm (green) LEDs generally have a much higher lumens per watt rating, and you never see infrared or UV LEDs with efficiency ratings measured in lumens per watt. They are instead measured with a simple percentage. Basically, a 100% efficient green LED is going to have a higher lumens per watt rating than 100% efficient LEDs of any other colour.

Great video, and very informative. This topic may be the answer to why some newly installed street lights in Dallas have a strange blue orb above (what appears to be) a standard street light. Many of us here have openly wondered aloud about this strange new design, and its purpose. Any thoughts?

I like the cold ligth on the highway.

R.C. Whitehead LEDs don't inherently flicker , it's just a poor power supply design.

i'd rather have no lighting at all

I prefer the bluer color over the warmer light. I seem to be the only one.

What about using some kind of traffic control to shut down or dim lights in areas where there isn't traffic?

Oh gosh, why it's so pleasing listening to this guy? Anyway, I love space photos of cities at night, without light leaking up, streets will probably be way more defined in HD pictures, making then look even better, and let me ask you this, is there any city with a night light with this kind illumination?

When driving on highways maybe disrupting sleep should not even be a consideration. Keep people awake!

Joey Riso The problem is light can still reflect off the road (especially if it's wet) and up into bedroom windows. It's pretty much impossible to prevent street light from entering windows entirely.

When they swapped my sodium lights for LED's on my street (and moved them to the other side of the road) I had to change bedrooms to one round the back of the house. Even a blackout blind was not enough, light still bled in around the edges and it kept me awake. I've also found while LED's are better for vision when driving when they *are* there, the transition to unlit roads is more dramatic. It seems to disrupt my night vision, everything seems a lot darker than when I pass through an area with sodium.

The newer LED streetlights in New York City have a pale, yellowish-tan (moonlight) color — similar to incandescent lights (around 3000°K). These were presumingly installed after numerous complaints about the earlier blueish-white (5700°K) LEDs.

LED street lights have very bad impact on wildlife.

"Who knows what lighting we'll have in 40 to 50 years?" Actually, we'll have laser lighting 10 years later, which is already used in some German cars overseas (they're banned in America unfortunately).

Am I the only on who prefers the bluer light aesthetically, yes it disrupts our circadian rhythm but it’s just looks nicer

good video! very informative. lots of kind of video. one thing. heat and how and were heat is produced. i cob leds vs white diode . im interested in more lighting info.

Dude, if people are driving at night, you want people to feel like sleeping???

How long would you need to be exposed to 5500k or higher light in your commute for your circadian rhythm to be disrupted? Instantly? An hour?

it seems that a light with a wavelength of 500nm would be ideal for day and night conditions.

1:10 Not true: Moon temperature 4600K, sun temperature 5500K. The natural night light is almost 1000K warmer than the day's natural light. During the day, the sky is blue, during the night the sky is darker blue. It doesn't mean that the night is bluish.

I'm really happy for this. At my country, they are still in the 6400K light. And no complaints are accepted.

+ps tasman very interesting. So strange then why night sensory cells evolved around wavelength that is actually less intensive than rest of the moon light... But it answers my question. Basically the blue light in moon light is less intense. So it doesn't impact our cycle. Because the cell does not care about the spectrum it cares about the sensory response

Actually, it is not. The moons light is much warmer than the sun's light. It is shown even on the documents on the video.

I'm a recent subscriber and I have to tell you your content is top notch. Good quality information, great presentation and amazing technical insight. While some people don't enjoy technicalities, I really like the videos you make: they shine a rigurous light on many interesting and varied domains. Thank you, and keep up the good work!

I have switched all my lights to blueish(really prefer white) leds. I absolutely love it. I hated it at first and just wanted to be more efficient. Now I love them except 1 thing. Everyone who comes to my place thinks it is super bright, but I have the opposite effect, I find the lights do not give enough light. Something about this blue light honestly altered the way I perceive light in my home. Making things seem darker. I don't know if it is better to just get a more powerful bulb next time or to get a different color/warmth/whatever.

LEDs run off DC, so any flicker is due to poor power converter design. Also our night vision eyesight is optimised in efficacy for moonlight which is bluer/cooler white so LEDs can be better matched by colour when compared to yellow/warmer Sodium lights. This results in better night time / low light vision and energy savings.

typically the "igniter" is omitted from the drop in replacements... as it's only used to break down the initial voltage that has to be overcome to strike an arc.

the main reason we use HPS is because of blue light sensitivity anyone that sits in front of a PC monitor without a blue light filter for hours a day knows this with blue street lights truckers would have to take more breaks because of headaches blue light might fix other things tho like urban center light bleed making the sky seem darker closer to the city

Health should be considered as number one priority. Blue light at night can cause sleeplessness. The improved visibility and safety of cooler lighting is marginal in comparison to the damage done to sleep cycles of massive amounts of people.

Disrupted sleep patterns on their own can really hurt a person.

I personally feel like I can't see in proper 3D and can't judge distances well with LED streetlights, mainly because it's usually many small LEDs with cause shadows to be washed out.Those aren't things I particularly enjoy not being able to do whilst driving a car. Also I frequently see LED bulbs flickering which either has something to do with me or the particular bulbs. And a cold light on your way home at night just looks unfriendly. :/

As an amateur astronomer living in a huge city (Buenos Aires) I have some experience with different types of light pollution. A couple of years ago the whole city used HPS lamps and some Mercury vapor ones. Without proper reflectors they produced tons of pollution. Nowadays every lamp was replaced with 5300K LEDs with awesome designed reflectors. But the pollution isn't easy to compare. In general, for visual observation without filters, sky quality has clealy improved. With some friends we estimated it at least one star magnitude better, that's quite a lot. For objects (some nebula and planetary nebula) that emits a lot in the Oxygen-III spectrum, visual OIII filters were great with HPS lamps. They are useless with LEDs though. For deepsky long-exposure photography, some people used narrowband filters (H-alpha, O-III & S-II) with great results with HPS lamps. They are having mixed results with LEDs, we think that not every brand have the same spectrum. Professional observatories use high precision filters, and as you already said, LPS are easier to filter. Hope this helps, and sorry for the bad english.

Lights that dim automatically are actually a thing... at work, the newer LED lights in our parking lots have motion sensors which keep the lights dim unless there's motion, when they brighten.

I don't have data to show, but blue light really bothers my eyes. The effect is more intense (or just more noticeable) in the absence of other colors. So, sunlight doesn't noticeably bother my eyes, but higher color temperature CFL and LED bulbs do. As do the "white" backrounds on computer screens. I've never been much of a fan of blue light, especially blue LEDs. It wasn't until recently though that I made the connection between the blue color and my eye fatigue. I stumbled upon a red overhead light source in the vehicle I used to drive. When using this at night it had no ill effect on my eyes and didn't even cut down on my ability to see the roadway. The blue and even white lights from LEDs and dashboard backlighting however irritate my eyes and actually make it harder to see past them to the roadway outside the vehicle. I often find myself dimming these blue biased light sources or, in some cases, finding ways to block them out completely. Tape over the blue lights on the dashboard or computer backrounds with black or other dark colors. Simply put, I've learned that light sources with more blue cause greater eye fatigue for me, as do many types of backlit LCD monitors (CFL is worse than LED, though possibly due to over all intensity). At home I find the best compromise in color and illumination comes from bulbs that emit in the range of about 2700k up to about 3500k. Anything higher starts to bother me. The only blue illumination that I truly find pleasing is that of Spaceship Earth at night.

Liking these videos should be taken for granted.

I would argue that the LED lights especially the ones ppl put on there car headlights are worse for safety purely cuse the frustration and physical pain these cause to my head has definitely made me consider running some ppl off the road it would be a service to society. I dont care if the light source is HPS hell I dont care what creates the light source at all as long as it is a orange/amber or even red color. the warmer the better.

I feel this video is the equivalent of a master's thesis on street lights.

the greenish aspect of LED ilumination irritates me much more, and, of course, is aestechcally worse

It's amazing that I drove on 88 enough to notice when the nighttime illumination improved dramatically, but did not notice the color shift as a factor in this improvement. Thanks for making this instructional piece to clarify the types of light being emitted by various technologies.

In winnipeg there half way replacing all streetslights to leds and i now see stars

As an astrophotography hobbyist I thank you for mentioning light pollution. And what the hell, "blue light ruins your eyes"?! lol.

I really dislike this new white light fashion. White lights seem to cause a lot more glare when driving on wet roads. Also fog penetration is very poor, instead of seeing through you can only see the fog itself. The yellow lights seem to be much less painful to look at

Chicago has used the same streetlights since the 1970s.

I miss the old Mercury lights of the 1970s. It used to give off a blue green color light.

If I'm honest... I would prefer SOX and Philips CPO-T were more commonly implemented in new installations instead of LED. it's more efficient than LED and produces a metric butt-tonne of light. Especially on an electronic ballast, the average system efficiacy (including the ballast's slosses, which are about 3-5 watts) is between 110 and 175 lumens per watt (115 to 180 excluding gear losses) depending on lamp wattage. The best an LED can do is 130 lumens per watt excluding gear losses. Not to mention at that LED efficacy increases with lower CRI and higher colour temp phosphors as unlike MH or MBF-U lamps, the phosphor has a reducing effect on efficacy. When LED technology breaks the 200 lumen per watt boundary and luminaire designs allow the fixtures to last more than a couple years, I think that's when LED should become the absolute norm for street lighting. It's still early days for LED technology against the mighty arc lamp!!

a good compromise might be to have different colour temperatures in different places. warmer lights for places near where people live, and cooler lights as you get further out of town. when you're driving in town, you'll theoretically be going slower anyway, so you'd be safe enough with a warmer light, but when you're going down the motorway, you are theoretically going faster, so you'll get more of the benefit from the bluer lights.

LED lights are cheaper then either Low Pressure Sodium Vapor or High Pressure Sodium Vapor lamp and it does save energy. They should do it to Dearborn Michigan and should be 100 percent for the entire city of Dearborn in the next few years, like they did it to the city of Detroit months and years ago.

I think we should go with bluish yellow lights.

i wouldn't mind if they removed most street lighting, Just keep em in busy streets and intersections. It would be even more energy efficient as well.

you didn't mention the cost advantage of using LEDS due to their long life expectancy. They don't require bulb replacements like HPS, and over their life span they tend to maintain their rated output efficiency much better than other lighting types. HPS, MH, MV, LPS, fluorescent, etc. All output light in all directions equally. This results in more than 50% of the light needing to be redirected towards the intended target using reflectors and lenses. Any time light is bounced off a surface or redirected with a lens, some of this light is absorbed or lost, adding to the inefficiencies. On the other hand, LEDs produce their light in a much narrower spatial distribution. instead of 360 degrees of spread, the light is limited to a 180 degree spread, with the majority of the light being focused within the center 120 degrees infront of the LED. This distribution band can be narrowed to even smaller angular spreads such as 90 degrees depending on the application, with Lenses being used to focus the light on target further still if required. The drive circuitry for LEDs will no doubt in the future have functions implemented to further improve efficiency. Some basic examples of this would be to dim the output at sunrise and sunset, or increase output during rain, snow, fog, etc. Also, sensors in the roadway could be used to detect when light is required and when it is not, reserving full light output for when vehicles are actually on the roadway, and only partially lighting the road when it is empty. This type of control requires circuitry that is not commonly used to power HPS, LPS, MH, and MV lights, making it unrealistic to implement on those lighting systems. LED lights are driven by circuitry that is already suited to be controlled in such a way and can be easily dimmed, brightened, or quickly shut off or on with little to no additional cost involved.

people were calling emergency services because they saw the sky like it's supposed to be... are people really that stupid??

Wow - great overview of outdoor lighting issues! You covered a lot of ground! Several issues that did come to mind were: 1) I don't find an issue with disrupting circadian rhythms with street lighting. After all -what are you actually implying - but that this makes people STAY AWAKE in the presence of bluer light. Ask ANYONE who drives a truck, taxi or works a nighttime shift involving driving (police, fire, ambulance). These people NEED to be awake and blue light facilitates that mindset. 2) You touched upon the solution to light pollution: LED's that dim. This is also a way to save more electric power - much more. You see, lighting elements that detect infrared can be used to adjust the light output based on heat signatures of engines or animals. Lighting in unoccupied areas can therefore be dimmed substantially - even kept off. Because LED's can respond to brightness demands instantly without stressing the LED as they have no warm-up curve - it makes them ideal for this. This can be done on roadways and most certainly should be done anyplace where lighting is used to assist pedestrians - such as parking-lots, parks & other places where people on foot benefit from the light but where no light is needed otherwise. From a SECURITY perspective - lights that are normally off, but come on in the presence of animals/people are actually much better security devices because the light itself announces when it "sees" someone. Modulating light sources to adjust for actual illumination NEEDS while being energy conscious could $ave a fortune w. energy management and also substantially reduce or eliminate light pollution. See also Dark-Sky movement:

So in Europe, they're actually using LED street lighting with sensors that detect vehicles and brighten the lights ahead of the vehicle while dimming them once the vehicle has passed the lamp. The ultimate would be combining a color temperature shift with presence aware dimming. Given the rated lifespan of these LED lamps, it's not beyond reason to think this will come eventually due to addressing pretty much every use case and every weakness.

This is Lombard/ Oak Brook Illinois

Before the Mercury vapour lamps, we used INCANDESCENT bulbs. Big buggers. They put out the warm white like you would have seen in the old incandescant headlamps. Mercury vapour was a new light and because of the color was deemed the light to have and they believed the white light let you see betteer. It was an expensive change out because you had to replace the entire fixture to run the Mercury Vapor. -- Hi Psi Sodium lights came with its orange hue but the only thing streets and san heard was THEY RUN CHEAPER... Everyone was buying and installing them. The problem I was told between Mercuy and sodium fixtures was that they were not compatible. You had to change out the entire fixture again. This is not to say that a Sodium bulb won't run in a Mercury fixture, but the ballasts work at a different power curve and the Sodiums will burn out faster. Another cleavet was that Mercury bulbs could burn until they stopped working. For most of their life they would have a very bright light output. However the SODIUM lights had a time limit. They are only good for X amount of operational hours. After that point, even though you are seeing light output, you are supposed to change them out. Part of this reason is the lighting element in the bulb will begin a long and slow dimming process where at the near end of life the bulb is dimmed down until it is barely brighter than a candle. Depending how how well the ballast is built, when the bulb reaches this state, it can burn out the ballast as the bulb dies. -- The new LED technology is interesting. You can pick up COB leds at most electronic parts stores now and make your own lights with dimmers if you want to be fancy. You can get them for most common voltages and one Cob LED will light an area very well. We are starting to see the LED street lights being installed both at service stations and on light poles along the streets. For the new street lights, the common color is bright white, which has a similar blinding affect to HID and LEDs on cars. You have to look at them directly but they are so bright you won't be proned to do this. They are easy to inrease light by just adding more LED elements. These also come in kits and are rather cheap to purchase. Very cheap to run and would light your back yard up rather easily.

I wonder if this is something they also consider in the outdoor lighting problem. Which color light is worse for vision when you leave a brightly lit area, and/or are frequently transitioning from lighted to unlighted roads. Its not likely to be a big concern in a place like Chicagoland where you'll usually be driving in brightly lit areas almost exclusively (though having once lived in the far west suburbs I know quite a few places where lighting alternates between widely present to non-existent). Outside big cities, and especially at interstate off-ramps outside of cities, going from unlighted highway to a cool light LED flooded off-ramp is rather blinding. After you've passed the ramps, you return to headlights only and it seems abnormally dark for a couple minutes as your eyes readjust.

Your feelings are irrelevant though.

Why not inductive lighting. Please explain more. It seems broad spectrum long lasting and efficient.

Someone from my city's department responsible for street lighting told me that warmer lighting performs much better under foggy conditions. Anyone has any thoughts / research on that?

"assuming the driver and heat sink are robust enough" makes me think of people (drivers) crashing in to lampposts (heat sinks)

Our city is moving over to LED because the manufacturer of low sodium bulbs is discontinuing them, and that they save energy. Ours can be configured to be dimmed if residents complain that it is too bright.

I don't understand why people prefer the old yellowish high pressure sodium. I find them very beamy. The yellow color screens the surroundings making your eyes work harder and judging the color of everything around you. I love the white LED lights. The light is less harsh and spreads out further. It's more relaxing and appreciating to my eyesight.

This is a fantastic, detailed comparison of LED lighting vs. traditional lighting. Great job!

Technology Connections The thing I don't understand is why we're still aiming fixtures straight down. We have great control with LEDs which should be used to solve the melanopic problem for the non drivers but also to solve a personal pet peeve of mine, which is that I shouldn't see the light source when Im driving either. Coverage in a forward and downward direction would be better but as far as Ive seen, it has never been considered. Heck, even the low pressure sodium lamps should be able to have a retrofit shield and lens system to do this. It can be done optically (look at modern headlamps)

525 nm green covers both well as well

Solar freakin' roadways

Who cares if it's cheaper? All your municipalities want to do is save a cheap few bucks a year for shitty Chinese Cree crap street lights that have not been tested to their claimed lifetimes yet. Also, I'm not even surprised Detroit went right away with the dumb LED bandwagon considering they were so poor they had to shut off street lights at night before LED conversion happened there, how hilarious

illiteratebeef my thoughts exactly. If it can keep you awake than it would be beneficial. I think this is also why some blind spot mirrors have blue tint claiming it’s easier on your eyes

Anyone else find it hilarious how he hates on cool color temperatures but uses them as the lighting in his videos?

what about mercury vapor discharge lamps? those have a better rendering index and blue light

I don't agree with the aesthetics argument, because that's mainly down to preference. I love the much whiter 5500k LED lights for my study and for my living room. I love the daylight aesthetics. Same with car headlights, most people do like the look of the Xenon or LED headlights' aesthetics.

When Portland started upgrading to LED it became harder to see on the roads, and more difficult to see people sneaking into your yard. It's probably an issue of implementation and cost cutting, but it annoys me that we had better lighting before the upgrade.

I agree with you, Leonardo

Just close your venetian blinds. End of problem.

Just close your curtains or venetian blinds.

Excellent video!

By 2020, R.I.P. Mercury Vapor Lights, R.I.P. Sodium Vapor Lights, either LPS and/or HPS. Hello LED Street lights.

3200k HID bulb is yellowish tint. HID come in all sorts of output colors / lumens 2600k - 12000k etc... They install the 3200k for FOG LIGHTS! White / Blue / Infrared lighting is terrible for fog.

IMO the fact that they can seriously impair people’s ability to sleep is a good enough reason to not use blue/white LEDs in neighborhoods. Since you want people to be awake while driving, using them on highways makes sense. They also turn night into a hell scape for light sensitive people like epileptics and migraine sufferers.

If we move to a bluer LED light for night driving, would this alter our circadian rhythm enough not to fall asleep at the wheel?

i will fight for my orange lights

While watching the video, I totally thought of this.

Residential is still all incandescent and sodium, pull onto the highway and it's mostly LED, the mixture of light temperatures at the border, messes with my eyes a bit (just what one needs when merging onto a highway!) but if just in one or the other, both aren't bothersome...I do like they replaced the entire fixtures with LEDs that point down and really illuminate that road.

Would it be possible/doable to tint the pavement? Other objects would still be lit up properly, but the majority of the light perceived by drivers would still be warm.

why so much on sub 3000k and above 5500k lights, and not covering 4000k to 5000k pure white wavelengths? The 6000k to me are horrible, just too much blue, and in household bulbs just look like blue lights, in superbright (50w and above) it's not so noticeable, but just still look so unnatural. 4500k looks so much better and not so unnatural feeling, but are not that common in leds, but 5000k is the most widely commercially available light that isn't too blueishly tinted. Even the chart you had jumped from 4000k to 5700k, leaving the whole "pure white" range out.

Alot of street lights around me and my subdivision have started to be replaced by LED's. They seem to do a good job lighting the area, but they don't seem to have the coverage the old fixtures did. They light up right underneath them really well, but not say a few feet from the fixture. Also, IMO the light up the road better in rainy conditions. I usually have a hard time seeing at night in the rain when driving under a non LED fixture. So I think the change is good.

Some decorative fixtures are actually dark-sky friendly. Many large sports fields are lit with light very tightly focused just on the field. It's quite remarkable. Have you seen one? I find visibility just fine with HPS. And it seems very bright. I was surprised about it not matching night-time vision. With LPS lighting everything is sharp and in excellent focus. I think this is because you're getting light of a single wavelength, and your eye doesn't have to struggle with different colors, which tend to focus slightly differently from each other. And they're incredibly efficient. Color rendition stinks, but do you really need it for safety? Why do you say that HPS contributes less to sky glow? Sky glow almost always has that characteristic orange color. Melanopic lighting is a double-edged sword. You don't want to disturb the daily sleep cycle, but you also don't want sleepy drivers! You are never going to see anyone reduce light levels. I've never seen it happen. Ever. You know those tunnels which have extra lights at their entrances for daytime use, so that you don't get thrust into relative darkness? They should be on only in the daytime, and shut off at night. But they're left on 24-7. I guess they figure more is better, they've got the lights, might as well use them. Then there's the possibility of lawsuits if the lights are turned off at any time. Arggggh. You're repeating things a little too often. It's a complicated topic. A transcript would be great. I greatly appreciated the lack of music. Music is always distracting, making it harder to follow the narrator and think about what's being shown and talked about in the video. Thank you!

Oh, and there are those people driving with blinding fog lights, driving lights, or WTFTC. Please, people! They're blinding, and almost always look like terrible.

I wouldn't mind the Xenon and LED lights so much if they would be kept on the road and out of my eyes. And almost every time I drive at night there's some fool with his high beams on.

He's talking about nighttime lighting, which he says has different requirements in color temperature. Use the right tool for the job. Different jobs may require different tools, or different lights.

Noah McCann buy curtains, problem solved.

Thank you for the well thought out video. I hope that people who are making these decisions are taking all of these facts into account. I usually hate all streetlights especially in the rain.

I really didn't want to know this much about street lights.

I would love to hear the 911 calls from people afraid of the night sky.

I don't know about street lights, but the Cree bulbs for residential use come nowhere close to the life that they claim.

i prefer arc sodiums considerably.

You said 3000k light dont interrupt sleep much but who wants to sleep on road while driving?

Very informative. Also good job on describing the trade-offs rather than just knee-jerk picking a side.

Circadian rhythm doesn't matter if you shouldn't be sleeping at the moment, aka driving on a freeway.

If you want to filter out led light you can get specific LEDs that only output specific freqenses of light

I live in a small village in Italy and the municipality just replaced the old street lights with new LED lamps. The lamp is completely flat and the LEDs are arranged in a rectangular matrix that points vertically to the street, so there is no waste of energy.

Ok only a minute in so you might mention it. The blue light from led is less likely to make you fall asleep then orange light is

Sky glow is illuminated atmospheric haze the exact same thing that makes sky blue, the sky object that are not as bright as illuminated atmospheric haze won't be visible on the sky thtas why you see less stars in the city, also making our sun the biggest light pollution source in solar system and reason why you don't see stars at all ;p Even moon 2nd brightest object that goes up to -12.7 magnitude (the more lower the brighter) on the earth sky have trouble to pass thru the atmospheric haze illuminated by sun, also moon as being 2nd brightest object is also light pollutant, making new moon phase the best time for sky observing.

Led street lights are poor and patchy. Sox low pressure sodium far better orange light. Plus low pressure sodium is the most efficient light source more lumins per watt than led

Light characteristics are measured in its color or K value. The interesting point in having orange light is that the lower on the spectrum light is causes minimalization of a "shadow" based on the wavelength of the light as it travels in the air. Red color does not work well in our eyes in terms of luminescence and causes more black and white effect when you look at something in "red light" (ever notice the light in a dark room for developing film?). At Orange/Yellow light at 3000K or so, we are able to distinguish colors somewhat accurately, and shadows are nearly eliminated. When you look at bright white light such as 60000K and higher, a very stark shadow is formed which causes us to see half an object while the back side is completely blacked out in the shadow. The use of the orange lights for street lights came about from a study in the 1960s in terms of safety for driving and pedestrians walking in streets in terms of seeing while driving and walking at night. The use of sodium lights came about because of elimination of shadow effect for drivers and pedestrians then. Hope that explains how and why a little...

No, your body will want to sleep regardless and you will fell asleep just by being tired, body naturally goes to sleep when body is weak and low on energy, circadian rhythm only helps to maintain regular pace of sleeping even if you not tired, as you won't feel asleep if you sleeped too much already even at night and with warm light around you you body is simply too active. From my life expirance, working standing is the best (non-chemical ;p) way prevent sleep as you body i working out just by standing, but ofcorse it is not healthy as any method that keep you awake when you not suppose to.

*Sky Glow* _Staring Tom Cruise_ Coming This Winter

Higher Color temp=Harder to see road when weather is bad. everyone like Why everyone want 'White Light' . It looks cooler. Car companies and car owners ditched '2xxxK' Lamps. every new car's frontlamps are white now. to Car companies, Make it Yellowish. i wanna survive in rainy day.

I absolutly hate all the yellow and orange lights, they are hideous and do nothing. I think the Amber LEDs are the way to go, their not blaringly bright but also work better then the ugly high pressure sodium.

I was actually brainstorming another idea: eliminating public lighting altogether and raising private lighting standards. Even that would have pros and cons. On the one hand, this would require motor vehicles to meet higher light-output and broader directionality. It might also require new laws or bylaws forcing cyclists to attach lights to their bicycles from sunset to sunrise maybe under threat of a fine for not doing so. It might also make it less convenient for a pedestrian to go out at night without a head lamp or flashlight. Another problem has to do with a car light failing. This means that legislation might require a car to carry a backup floodlight that a driver can ignite at a flip of a switch should the main lights fail for whatever reason. After all, if there are no streetlights to light his way aside from traffic lights and sign lights, then he needs to carry his own light and backup light sources with him. While the lack of public lighting might not necessarily increase the crime rate, it would most certainly increase the need for motion-sensor security floodlights and security cameras on private private property to deter crime none the less. On the other hand, it could reduce municipal taxes to compensate for the extra cost of extra private lighting, and would give a person at least somewhat more control over his light source. For example, a person could choose for himself what degree of kelvins he wants for his car or bicycle lights or even head lamp or flashlight. It could also give him at least somewhat more control over how much light he wants. For example, he could go into a large municipal park guided by a flashlight and once on location, switch it off to do whatever he's planning to do, whether to look at the stars, appreciate the private lighting from across the river (mostly from car lights, balcony lights, flag lights, etc., which would probably still produce a beauty all its own but without as much sky glow), etc. The above solution would probably still cause sky glow, but certainly on a much lower scale than now. The cons might outweigh the pros, but I still thought it an interesting brainstorm if thinking somewhat outside the box.

There is just one thing that I would like to point out, the last part of the video about luminous efficacy of LED, the luminaire chosen from Cree was a very poor example of where we are efficacy wise, most of the LED have efficacy of at least 100 lm/w nowadays (for outdoor) most of the indoor stuff is now around 130 lm/w (affordable option) high end luminaires are around 160 lm/w Most of the products that are used by cities (cobra head replacement) will be required to be listed under DLC and the minimum requirement for DLC standard is (at the time of writing) 90 lm/w, where I think it goes up to 115 lm/w for DLC premium. DLC is mandatory 99% of the time when you are dealing with cities or government.

In our area in the UK, they just turn the street lights completely off at midnight... except in busy areas... or on weekends... a 50% dimming would be much safer... its kinda scary when they are all off and you are out to be honest... I think they are doing it for some cost saving reason, they are LED lamps too.

I hate skyglow.... I live near an airport ant this is by far the worst... Even more worse than an Plain.

If it's boiled down to efficiency vs aesthetics why is it even an issue? Aesthetics aren't an engineering concern unless they have no impact on function, it's pointless to talk about worthless aesthetics as a counterpoint to measurable increases in efficiency/ effectiveness.

I fucking HATE blue light, it's the worst thing in the entire world

My city switched completely to LEDs. Residential areas have warmer temperature LEDs, other areas have gone for the cooler temperature. I am definitely a fan of this.

neat! :) We could use more street lights around here I tell ya what!

Blue light may not ruin your eyes directly, but what it does is massively increase eye fatigue. You can try this for yourself and it more convincing than any study you can find. Wear a blue light filter glass for one day, if use computer daily, that even better. The next day stop wearing it, sometimes after the sun had set you would feel an unusual amount of eye fatigue. THAT is the fatigue your eyes get every day, it's not something new, it just that yesterday you were wearing blue light filter glass and don't feel this fatigue. Even if you don't want to buy a light filter glass, on PC you can install a program called Lightbulb, it changes the color temperature of your screen. Tune the color temperature for the night at about 4000k. Now disable the program, use the computer until you're about to turn it off and go to sleep, try turn Lightbulb on and experience immediate eye relief. If that doesn't convince you blue light fatigue your eyes more than any color, I don't know what. Try it, it free. Also when you think about it, it just makes sense that blue light make our eyes work harder, because it present day time. We animal didn't evolve along with artificial light sources that can light up like the sun (lcd screen and led light), so our brain treats blue just like sunlight and make us stay alert.

I do a lot of studying at night. I have three lamps that I can use for work. One is a bright and harsh blueish-white led. Another is a warm yellow led, and another is an Edison bulb. I flat out hate the color of the yellow led. It produces a color that is not cozy or aesthetically pleasing. The Edison bulb on the other hand has a rich warm color that makes the room comfortable, but it puts me to sleep. The blue LED is good for concentration, but it's harsh and not pleasing to look at. I found a really nice combination, where I shine the blue led across the Edison bulb. It creates this fantastic bright white-indigo-purplish light that is great for focus, but just as cozy as the led by itself. I think the idea of combining warm and cool lighting is the answer. This way our roads can be safe and comfortable at the same time.

Finally! A way to save money and keep people alert and driving on the road for longer! -toll road owners

You're a really observant one, Technology Connections. Well done!

Use green LEDs for street lights then hahaha. Right in the middle of the scotopic peak!

500 nm is green-ish. Is this why night vision goggles produce green images?

Lighting things up which are not the road is actually not dumb Liverpool residents have recently had issues with increased burglaries due to reduced lighting because of LED's. The main issues with the LED lighting recently fitted in the UK: 1. Lack of diffusion - probably to get away with less Led's and less power this results in more of a spot light 2. There's not as much light being emmitted from the Led lights this is probably to council's cheaping out and getting a low as possible light source and because the blue light is too harsh 3. The new lights can be switched off remotely, which sounds good. Untill you realise there's now large stretches of roads in the North with the new lights turned off to save money So regardless of frequency reponse which this vid focuses on, these types currently make the roads less safe due to the temptation to abuse the technology by councils to save as much money as possible It's now cropping up that there may be cancer risks, and sleep issues Personally I'd like to see LED's with the same colour frequency as the sodium's (warm yellow / orange), with diffusion to spread the light out and more LED's for more light.

What about metal halide?


+Tyrone I have had mixed results with LEDs in industrial environments. They don`t hold up real well to high heat applications and the driver quality leaves something to be desired. You really have to watch the brand because alot of LED makers use crap chinese junk LED drivers that fail quickly. It is a high profit margin industry with marketing being more important that actual quality.

Sources or it didn't happen.

Where I am there is barely any street lighting and everybody I know from the city freaks out and is afraid to drive after dark. If you get used to it like me it's the same thing as driving during the day you learn to spot out stuff on the road after all thats what headlights are for.

Why should the fixture be aimed straight down without a diffuser? It's literally an eyesore to look at. The new LED's just blind you with the veiling glare and you can barely see the ground, but high pressure sodium actually diffused the light and let some of it escape, it's not a problem if you are able to see the light source from above, cities look so beautiful with it. If they upgraded to POS LED's, it's a downgrade. How exactly does the orange light make you sleepy when you're driving, what an insane thing to say. High pressure sodium was the way to go for the world for more years, but unfortunately they would rather upgrade to a cheap source of light that isn't even a lightbulb and guaranteed to fail less than 5 years.

what about amber leds??

Who paid the studies ? Sodium lamps are brighter and thus better.

They also work great as a deterrent for late night park walks. Tbh I hate my city for putting cold, greenish tint lamps in the parks and squares.

Less melatolin may be desirable on the road. Might reduce the amount of people falling asleep on the road.

Blue lights blind you! EDIT: There also studies that say they cause cancer, as well.

Have any municipalities or companies experimented with dimmable, variable color-temperature LEDs for outdoor use? Seems like that would be a safer investment in that they could dial in the specific temperature they want from a centralized control center. Cooler in the evening/morning, warming during the night. Imagine a whole city following a circadian rhythm! They could still stock a single, standardized bulb while tailoring them to better suit particular areas (brighter and cooler in commercial, dimmer and warmer in residential). Maybe even a softer amber glow in parks or wilder areas. All with the same bulb and the same controllers. Heck, you could even mix in some RGB bulbs in public gathering spaces to enhance holiday cheer. ;)

Shouldn't the goal of artificial lighting be to as faithfully reproduce actual lighting (sunlight) as possible? To that end, I believe 5000k "daylight white" LEDs are generally the best default option. Only when you specifically want warmer or cooler should you stray from that mark.

Yeah disrupting circadian rhythm. Is a good thing we don't want people falling asleep behind the wheel. Set the lights on small street to the warmer tones.

Another issue with LED not addressed in the video is the driver issues. Most LED's use pulse width modulation circuits that react differently with power fluctuations, low voltage drops and just naturally can make your brain react to them like a video frame-rate or flicker. When you look at a sodium or incandescent light burning its a constant light which is your eyes and brain don't have to process the extra data. As you get into the cool/blue white needed for optimal night brightness to the eye, the CRI gets worse and all color will be washed out more and therefore pedestrians and other issues while driving will be less noticeable. This exact issue has been happening with all the new cars using LEDs and projection headlights. You can't see a thing with oncoming traffic now in many conditions. Wet, snow, uneven road angle all leads to blinding the oncoming drivers. Now we'll put this LED technology to the street lights! My moms town recently switched to LEDs for all the street lights and its bad. Its gloomy and pitch black everywhere around the roads and on the roads and I can not see as well. LED's are a very small spectrum of light which is very unnatural.

I don't understand why he says it's complicated, or that there is good and bad. The choice is obvious. LED lights. You want drivers to not be able to fall asleep on the road. You want it to be easier to see. You can easily focus light where you want it and it's cheaper. Seriously there is no negative. It's not weighing the good with the bad. The choice is clear and if anyone says it isn't they are lying.

Am I the only one that found it amusing the way he stated at the end that cool light was aesthetically displeasing, as though it were a fact to be taken into account, even though he'd said earlier that this was his personal preference - _and_ that a study had shown people generally preferred cooler lighting in nighttime conditions?

Alex Atkin - okay but why can't municipalities use yellow-orangish LED street lights that are diffused? I would've preferred that just fine. Instead they have to use fucking warm white LEDs as if it is daylight but just a dimmer time of daylight.

+Tyrone Warm light DOES make you sleepy, its natural, its why most people prefer warm light in their houses as its warm, comforting, cosy. Personally as a cyclist or when I have to go to the shops at night in winter I find the new LED lights make me feel much safer as I can properly make out the environment around me. The old orange lights you can't see pot holes, mud, dog poo, until its too late to avoid them even with the best bicycle light so it was a huge safety risk cycling at night. As for it disrupting the sleep after people have driven home under them, that's mainly an issue with working hours. If you are driving home at night you absolutely should have enough time to for your body to adjust into sleep mode BEFORE going to bed. You don't want to be falling asleep while driving nor still wide awake once in bed. You can't blame the lights for your working hours being unsuitable to human beings.

I install metal halides as an electrician

As someone who also has driven on I-88, I would have to agree that the newer lighting is much better for drivers.

The best streetlight is no streetlight at all

I love the white/blue street lights, it is so much easier to see at night.

They just got to make the LED lights look more like regular lights because to me they look like fly swatters or how can I put this very alien I think appearance is important too and I honestly think when they do LED lights they need to look like more regular lights

There is something nice about the old sodium lamp, its nostalgic i suppose i like riding in a car and having the orange light fade in and out as i drive, the led lights are bright but they are harsh and not nice to drive under, but they are safer, and maybe you should be more on edge while driving

surely led carcadium rhythm is good as it will keep you awake on long night drives

There's a grocery store near where I live that has auto dimming lights in the parking lot. They're equipped with motion sensors that gradually brighten the lights in two stages when a vehicle or person on foot approaches - about 20 feet out they go up one step and about 10 feet out they go to full brightness then they go back to dim state after about 10 or 15 minutes of no movement. I don't know how feasible that would be, financially or logistically, to implement into city o highway lighting, but it may be a possible solution for residential or urban lighting where consistently bright lighting causes disruptions and problems.

You remind me of Adam Lambert. I guess it must be your speaking voice and hair.

Whoa I really thought it was near the end of the video at 8:00, boy was I wrong hahaha but a very informative sight, thanks!

curtains are great, and you want to be kept awake while driving.

I feel like I'm the only one who hates the warm colour of the high pressure sodium lamps

The only good thing I like about the GE Evolve LED's that are so much more common on small neighborhood streets with 70W HPS fixtures is that they look like incandescents. I wasnt born in that era, I was born in the sodium era, early 2000s. Only reason I like them. So stupid how a bright HPS is being replaced by some barely bright when it first turns on LED luminare

In this video I think you missed the point of Sodium Vapor lights. It was not to conserve energy. Back when everything was Mercury Vapor it had one huge disadvantage. Its absorption spectrum is close to that of water. During rain, fog, snow - any water in the air - Mercury Vapor lights ability to illuminate is cut significantly since the absorption spectrum is similar to water - it would be absorbed. Sodium Vapor lights were created to solve this problem. As we know, Sodium and Water are incompatible. Sodium Light cuts right through water - its absorption spectrum isn't even close - and its a similar technology to mercury, so it was easy to adapt. Foggy roadways were now visible at night. Snowy roads were visible. Yes, it may not excite the cones in our eyes but our rods are just as capable if not more so at making a clear picture out of lower light levels. Sodium Lights made a world of difference when introduced back in the late 1970's in the reduction of vehicle accidents at night. (I've looked online for documentation of these claims, but it was the 70's before the internet, I can't seem to find anything. This information is what we learned in Science class and through real life experience and news reporting of quantifiable evidence based on National and State governmental reporting.)

Leds are absolutely viable nowadays in terms of every aspect except cost. There have been more efficient chips and led light packages from companies for years now. Horticultural lighting is always ahead of consumer lighting by a lot and hps has been overtaken in efficiency for some time. The only downside is cost of course

LED sucks !!! And those horrible bluish white headlights. !!!!! TERRIBLE

Having a LED style light for street lighting is looking like the way to go. With the cost of power increasing and loading also increasing on a town of city level. Having a lower consumption of power demands on a town/city level will work. Possible way to solve the light from heading up by placing a reflective material on the sides to push the light back down. This could be useful with helping the street lights from invading housing.

I feel like Led lights are a lot better because you can get many other colors then 5k - 6k, you can get a 2k that is really warm or 8k that is almost blue light. Some led light also do something that high pressure sodium lights can't do that prevents light pollution and that is a sensor circuit that makes the led light dimmer if no one is around, but if someone or something activates the sensor that will cause the light to be brighter for safety and there is amber led lights or even color changing.

LEDs only light straight down on the street not the area around you that you need streets are bright but area around is very dark LEDs are like lasers plus they hurt like hell if you look at them and make you feel sick. But hey it's all about that money

this video is too good for youtube.

Maybe I'm just old, but I was used to street lighting with mercury vapor lamps and have been complaining about the sodium lamps since they replaced the the previous ones.The direct light from sodium lamps blinds me while the ground is poorly illuminated and pedestrians are hard to see. LED street lamps are far better for me and if they make me stay awake, so much better, because I'm driving.

I hate the new Bluish White LED street lights! They are using them here in Michigan. When I drive at night, I feel like I am back in the 1970s!

Only now that the days are short enough for street lights to be on while I make my home that I've noticed sodium discharge lamps being replaced with LEDs! They must have only been replaced this summer.

Our local utility company, PSE&G ultimately went with inductive lighting to replace their HPS fixtures. Thankfully the lens setup has them throwing light downwards. Some links below with more info.

Yellow lights don’t attract insects like white light does. I have seen street lights with white bulbs full of insects.

What about the dash lights and nav systems in modern cars?

Who knew something like street lights could be so complicated? I never considered the effect on wildlife. Very interesting.

The science here is really good and I never knew it (Spectral misalignment, etc). Not a big fan of cool temp LED's. Seems like my eyes don't see their light at night as well *Waste, even a danger to public safety.

I like warm lights but above all detest colour muting. In europe sodium has been here for the last 20 years, I can still remember how dark the streets used to be that said I can't wait for a fast enough conversion to led.on convertes areas I've noticed less brightness at the bulb but better spread, I recon both light forms behave differently, as in car headlights the lumen values on led don't drop as much with distance but are also not that high up close, perhaps the new lights are intended to be dimmer taking advantage of scotopic sensitivity.

Motion sensor led lights.

I disagree about light colors. Warm White....or what I call Smoker dull, ugly, and makes everything look dirty. I won't use any like less then 4000k because how disgusting it makes things look.

I like your videos, but they're mostly too long. There has to be a way to be more succinct.

Almost all the street lamps in my area have been replaced with white LED lights. There are now significant dark patches between each post where before there were none. The most dangerous aspect is that now, white light ahead could just be another street lamp, or an oncoming car, with no way to differentiate. Under orange sodium lights the white lights of a car are easy to differentiate. With a lot of single vehicle-width roads with blind bends and no sidewalk, this puts pedestrians at significantly increased risk after dark.

They recently changed the streetlights in my neighborhood to LED

the leds would keep drivers awake especially at 5000 k maybe they need to place those on major highways and use 3000 k or high pressure sodium in residential areas

When the roads are wet I can't even see the damn lines on the road because of the white led glare sparkling off the little puddles on the road. It all comes down to cost is cheaper it has nothing to do with safety.

does anyone else find sodium vapor lights easier to see in than LED? I've been told white light is best for night, but even with my flashlights I find LED very unnatural and hard to make things out in. On the road it's like LEDs are just lighting up the area directly under them as well and not diffusing the light across the road. I've often missed people walking up to intersections with LEDs where I never did with the old lights because they diffused so much light.

I prefer Sodium lighting because the Gold glow of it seems easier on the eyes and LEDs to me are a bit of an eyesore. They just look better to me.

I am not averse to intellectual descriptions, but I think this video would benefit from less jargon and repetition of points. This could have been 2 minute video and gotten the points across.

Love your videos. Very interesting and informative. I use LED bulbs exclusively in my home. I went from incandescent to CFL then to LED a few years later. The part of the driving video with the LEDs look more clearer than the other one.

The traffic lights in my city were changed to LED’s and now snow builds up on them, in some cases completely obscuring them because they don’t make enough heat to melt it.

The LED street lights near me in the UK are awful and not like the ones you showed in your video. The sodium lights give off a wide mild light whereas the new LEDs give a bright light concentrated only where the street light is, with very little light illuminating between street lights. There’s a park near me with a roundabout and at night time it’s almost impossible to see vehicles or cyclists on the roundabout because the street lights are so poor. I suspect this is a specific design of the lights used near me as the ones in your video are much better.

I recently got my first house, a lot of the fixtures had older incandescent or CFL bulbs. I swapped almost all out for LED bulbs I got on sale. Garage had giant 4FT fat tube fluorescent fixtures and like 1//2 of them never wanted to work right. I ended up finding some $45 lithonia bar strip LED lights for like $30 on clearance. I got a gob of those. I got 2 of them up, I like the LED a lot more than even the working fluorescent fixtures. It is more of a pure white, they come on instantly even in cold, and no ballasts, etc to fail or buzz. These were small enough to screw to the length of a rafter, a fluorescent would not do that without many inches hanging over each side.

They recently changed out the lights to the lens leds at a warm color here with 3 lenses. My home backyard faces a major street, the led has burned outbfor the 5th time within a 1 month period. The leds make the street darker here bc our lights are pointed at the top of an diagional arch making it hard to see.

My area has been upgrading many streetlights and some newer ones that have been installed in the last year have warmer LED street lights. I want to say around 3500-4000k where as the older LEDs are closer to 5000k or more. The warmer ones arnt exactly the yellowish color but it isn't pure white. Even my state has been upgrading some lights along the highways.

I suppose it makes sense that we may prefer blueish light, but when there is snow blowing across the road... no way. I remember driving on the highway with snow blowing and white LEDs; it was so hard to see the road. Then when the lights changed to the HPS (orange) lights, it was easier to drive. I'm not sure why, maybe it may have been because the white LEDs reflected off the snow.

LED, HPS, MV, HID, or whatever else IDGAF, what I want is for someone to get the assholes behind me to aim their shitty aftermarket headlights properly instead of directly into my fucking mirrors.

Correct me if i'm wrong but no one wants to go to sleep while driving. In this case blue is better.

LED street light look horrible. They don't feel right and I don't want them. On a side note, my house used LED lighting EXCLUSIVELY, but all of my bulbs are certified 95+ CRI from Japan.

We continue to be better on paper while the standard of life slips along the way. Very harsh and uncomfortable on the eyes

What if you're trying to have an enjoyable evening in your back yard and the ambient light of 5500 k lights of the street are shining into your yard. Curtains would not really work in this situation don't you think.

Do you know what disrupts your circadian rhythm even less than sodium lights? Darkness.

Aaahhh the good old orange glow of chicaoland. Takes me back to my youth.

This video has been... enlightening

I hate LED and Halogen lighting. Both honestly make me sick.

No CMH? Ceramic Metal Halide.. 4000K lamp is closest to the sun. Also, CRI(Color Rendering Index-sun is 100CRI. HPS is around 22CRI, MH(Metal Halide) 70CRI, CMH usually over 90CRI(98!). COB LED's w/optical lens 90°, maybe 45° even! Helping to avoid upward, outward, unwanted light pollution. And available from 2000K-7000K, giving many options. 4000K is a nice color. At 1st, LED's were very deceptive, our street lights were almost dark underneath, lol. But nowadays, about half the wattage of HID lighting, at most, yet with many more colors, and optic lenses, I don't know how the newer LED's can go wrong. "Well, when light dies, you need a new fixture, very expensive!", yet I believe you, or a professional could switch out the diodes quite easily, especially COB's, and after it gets more understandable, each time, and maybe cheaper than an old mogul lamps, if changing every year already. Some LED's offer a 7yr warranty. 165lm/watt! Streetlights! Great video! Very informative and I knew much of it, already! Thanks again!

Technology Connections It all depends on the color temperature they use aka the K scale a 5000K at 2500 lumens will be bright to see better but at what cost to our eyes and safety fog and in heavy rain and blizzard conditions will be a problem at night but if the output was 2500K at 2500 lumens will be a little safer. Build them that can do both color temperatures when the weather is bad use the lower color temperature but when the weather is clear no fog rain snow run it at the higher color temperature for better visibility.

It all depends on the color temperature they use aka the K scale a 5000K at 2500 lumens will be bright to see better but at what cost to our eyes and safety fog and in heavy rain and blizzard conditions will be a problem at night but if the output was 2500K at 2500 lumens will be a little safer.

I'm no lighting surgen but, wouldn't whale oil work best as a lighting solution?

I got tired of waiting for my city to install additional steet lights. So I installed a 2” galvanized pipe about 18 feet up just inside my property line. I use a 150 watt sodium vapor on a timer. What equivalent LED would I use when this light stops working? Thank you...great posting

I personally hate LED lights and other bright lights on vehicles while driving at night. Oncoming traffic is the worst. I feel like everyone is driving with their brights on and it's hard to see the lane lines.

HPS is one of the ugliest unnatural light sources ever invented.

+AutogolazzoJr That depends on your perspective. From the ground by naked eye the orange glare bombs make it nearly impossible to "stargaze", seeing as their contribution to light pollution is immeasurable, and as he states it's also due to poorly designed fixtures.

The good thing is that it's super easy to filter out the sodium spectral line for stargazing.

LEDs can be any color - any brightness - all consume less power than conventional lights do. Bad placement - lack of shielding - lighting the sky with upward facing lights = all bad practices that hurt life's rhythms.

I remember when Halogen lights for car headlights became popular. Yes they let you see better when you drove at night but they also blinded some folks severely when facing them.

while I agree that we should switch to LED lights for street lamps, . and while at night.. eyes are more sensitive to blue light, there is a caveat, eyes cannot focus on blue light as well as yellow. . this is due to the different refractive indexes between colors. I think just using white LED's is the way to go

What light do you like? Fluorescent?

He made a video on this.

This could possibly be the answer, but keep in mind that this is a personal experience. It must be tested in an experiment with controls and several test subjects.

Excellent video, very well researched, although it did make me think that we should just start developing cybernetic eyeball replacements/parallel augments

Yup, the blue light is "harmful" thing is just a BS fear mongering marketing ploy piggy backing off the real science that blue light does disrupt circadian rhythms. As others have said, LED lights are the best option because with motion sensors to dim & brighten the lamps they are not only more environmentally friendly, they're also more economically viable as they extend the lifespan of the light.

Wait? Not aesthetically pleasing?? Those orange lights are horrible. Looks old and backwards. LEDs look more modern and progressive.

I find led lighting just plain painful. And in areas where I get to be hit with it in flashing fashion as I pass by the lamps, this effect is pronounced. It's true though, that other light sources tend to be way less power efficient. Unfortunatelly there are also myths flying around that need to be put to light. One of the myths is that the LED lighting is way more durable than other sources. Unfortunatelly, that's not true, as LED's tend to hate AC and Pulse current and manufacturers just don't care enough to actually properly filter/stabilize the power supply. Also LED's absolutely hate moisture and their circuitry hates dust. Another myth is that the LED's will return to you quickly, in price of electricity. Unfortunatelly, LED's still cost quite a bit and as mentioned, their reliability isn't that great. Also compared to other sources, it's usually neccesary to double the amount of light sources to match the required luminosity or completely change the whole light fixtures. Another problem with LED's is that - Not all white is white. Manufacturers would go as far as making a light color lie and have the sources to actually work only in three bands of visible spectrum - red, green and blue. Which could go hillariously wrong as resulting perceived colors of objects turn out to be complete nonsense. It's sort of like putting a Native American, Afroamerican and an Asian next to one another and saying that in this configuration they are white. In a way that would be true, but not really. So I'd say that with a bit of regulation, technological precision/development and proper attention to detail, LED's will be very desirable light source in near future. Light source that will replace all other sources, turning them obsolete. The right colors are available, they are decreasing in price, now just to catch on to the reliability. Until then though, they are still overpriced considering their durability.

I say if we start changing the bulbs as we build and redo light areas we can fix the cloud palution as we build and change as well, and also reduce the thousands of kwh we use in given years reducing our overall power needs, thus reducing palution from non renewable energies.

IDEA: Centralized combined laser light source of perfect hue connected to a bundle of fiber optic cables distributed to many light poles then some sort of splitter/Fresnel lens at the head can recreate a bright enough surface. Sounds future-ish but ......

Why limit to 5700 or 3000 choice? Compromise at 4000. combine white and amber LEDS in the streetlight head to achieve it if needed. Also, circadian rhythm is given too much concern. Keep people driving at night awake! It's more good than bad. Once they get home they can sleep. Chances are they will be on a blue lighted ipad anyway or watching TV till all hours so let's worry less about their rhythm since they usually don't. As for HPS I've always seen them cause much more sky pollution than led but maybe it was caused by head design. The sky is looking darker and better all the time around here and I'm on a hilltop with cityview.

You're eyes don't know if its day or night, just how bright it is. So I don't see why you can't use the same parts of the eyes in a brightly lit street. I sleep with my LED bedroom light on for my old possibly partially blind cat to be able to get around at night. I don't have a problem sleeping. And if you are worried about lights waking people up, I'd like drivers to be awake.

You sound like that one person in Cities: Skylines who complains about farming.

If we use the spectrum that would disturb our circadian rhythm, then it may affect those drive in locally. It would be interesting to know the percentage of highway traffic that is local cross town ,or thru traffic. Those driving to 3rd shift jobs Those running out in the night for a host of reasons. My thoughts are that disruptions of circadian rhythm are not like having a cup of coffee or red bull. I think they can have lasting and more dynamic effect. But I am no expert in this matter.

+Joey Riso but you still get reflective light.

Warm White > Destroys your vision white (literally lost my vision in my right eye from working under several of bright white lights)

Most lightbulb sales calls likely happen during the day, so they want a lightbulb that looks good during the day.

You make great content thankyou I subscribed!

Just get rid of those ugly ass orange lights!!! Replace them with candles if you have to!! Whoever made that decision shouldn't have a job.

Why not just use LEDs that are of a warmer color somewhere in between white and HPS? All the benefits (cost and energy savings) of LED and lesser health and aesthetic ill effects.

LED is proven to be bad for your eyes.

When it comes to outdoors NIGHT LIGHTING... I personally don't like it because it tends to drive off those things THAT ARE SUPPOSED TO BE THERE, and attract those that are not... I say this from experience... I moved into our current place roughly 3 yrs ago and every night there were some sort of NATURAL critters running around, for about 6 to 8 months after the move in. Then the property manager decided to change the lights to "Scare off" the bad influence of people coming and using the "Hidden" parking lot as a place to hang out for some people... Well it caused just the opposite. The Wild life vanished and the "Unwanteds" got more apparent... And it's not like there isn't shadows to hide in, they just seem MUCH MORE DARKER now with the LED's than the Fluorescent lighting they had. And to make things worse I think it's because LEDs light up more of the FOREGROUND rather then flooding the entire region like the previous flood lights did. I have noticed this with my smart phone's light as well... I can take a normal old school mag-light and flood a forest with light and SEE NO PROBLEM, my smart phone's like barely lights up anything past three feet unless it's reflective in some way, which makes seeing in the dark so much more difficult, Why is that??? And well what I was saying to begin with, it seems because of specific lights on the street, I tend to blinded by some... Like Halogen lights, no matter how low they are turned, BLIND ME... I have always thought these being used as car lights... DUMB AS HELL... Sure the driver can see, but the victims of the bulbs can not at all and that's where most of the accidents come from... Animals, walkers, and cyclists who are off on the side of the road can not see what the hell they're doing from just one car and that sometimes ended up with them crashing themselves or wandering into oncoming vehicles...

Induction lighting was the way to go as far as maintenance was concerned, they lasted years and years. Led will give them a run for the money

19:19 Pretty much sums up a healthy skeptical, but still open mind.

Led for highways , yellow for neighbors ( to make drivers calmer)

I learned a lot from this vid. We had HPS all over the power plant I worked at which was built in the 80s and I found all their paperwork for why they chose HPS which was then very cutting edge. The lumens per watt was their main thing along with a walk around with a light meter so that x lumens were always present and if they weren't then install more lighting... it was interesting to see what happened. In any case I never really understood why it always seemed way darker to me than it should; I thought maybe my eye was just different even thought they always check out fine. Now I know!

but i like the current color tone :(

Not sure about HPS but... I don't like LED at all. I don't care what "science" saying about it but old incandescent light way better (except deficiency) and way more natural. I am getting tired way faster when I use LED.

Night pollution already sucks!

When using that is, obscure, vauge, or jargon; one should definitely such language so that it isn't a barrior to understanding. You used technical terms for various types of vision; without defining that terminology, thus creating a barrior to the listener fully understanding what you are trying to convey. If I do a video about computers in which I use such terms as, format, install, reboot, etc, without defining these terms which is jargon relating to computers and technology; I should not be surprised if listeners get confused and thus click away from from my video due to it's inability to further understanding of the subject matter. This isn't the only video in which you have done this, you should.look at other people's videos where they use such scientific terminology as you used, but where they do provide descriptions/definitions so as to further understanding of the subject. Just a friendly piece of advice, as I have to break down technical terms for every day people as.part of.job, and know how not breaking down termonogy can turn people.away.

HPS bulbs are less efficient at producing light versus power consumption. Where is the power wasted? HEAT! An important factor with LED fixtures is that the efficiency makes them cooler. In NH, a municipality switched to LED street lights, and the first winter after they were installed the lighting was barely visible through the 3 foot icicles hanging from them. The solution? They installed heating elements inside of the fixtures. There goes all of the efficiency gain...

The thumbnail reminds me of tokyo extreme racer zero lol (old racing game on the ps2)

Links? And arent all lights bad for you, especially if you look directly at them?

Never thought street lights would be so interesting

I had half a comment written before I saw this. I fully agree with you. Light that's good for falling asleep is great. At home. In bed. Not when you're driving.

Yes we love what ever floats through your head . lol

I know that LED street lights cause one hellacious of a glare.

Ratatat tat

THATS CRAZY THATS WHERE I LIVE! Also Groton is pronounced like rotten with a GR prefix. GRR ROTTEN

Thank you so much for this upload

Wouldn't we want people to stay awake at night?

The old orange light is better in the eyes for cars, it really ticks me off when a new BMW comes past with their beaming dam sun light LED bulbs blinding me to near blindness!

Welcome flicker now all city will flicker thanks to led

Using a wavelength that we can barely see AND which makes us tired isn't really the best idea for street lighting now is it?

So what is the white lights the look just like HPS lights? Is that the LPS lights you mentioned? In that case, we have a lot of those in Sweden, especially in neighbourhoods since there is less light required there.

Here's a compromise. LEDs where there are no residential areas nearby. Like open highways, middle-of-bum-f***-nowhere roads, etc. That way it'll only disrupt the sleep of drivers who are far away from a place where they can safely sleep anyway. Sodium in residential areas. By the time you're getting into these areas, you're probably close to home, or at least likely close enough to a motel or something you can check into anyway.

+TheLinkoln18 Not true, I had an LED street lamp installed outside my bedroom window. I can not notice any of its light coming through a normal non blackout curtain. I also notice that it barely illuminates anything but the street which is exactly what you want. The previous lamp before it would illuminate my entire front yard. I would let your traffic agency know so they can change your LED street lamp to one that is far more directional than the one they seemed to have installed outside your window.

+MrEdrftgyuji until a driver falls asleep and drives into said bedroom :)

Ur a nerd, it’s awesome.. I’d subscribe if I had some fucking drive to do something.. so safe to say, I’m over it.. YouTube’s algorithm gone wrong.. when’s google gonna know when I’m high

LED makes a cold and dystopic feel so I don't like it

Apparently the Los Angeles story was kind of exaggerated once PBS got ahold of it. According to an LA Times article on the matter, "So foreign are the real night skies to Los Angeles that in 1994, after the Northridge earthquake jostled Angelenos awake at 4:31 a.m., the _observatory_ received many calls asking about 'the strange sky they had seen after the earthquake.'" (Emphasis added by myself)

I'm an electrical lineman, and I was in charge of a lighting-specific crew for about 2 years. I have a fair amount of experience working with h.p sodium, mercury vapor, metal-halide, and L.E.D lighting fixtures/sources/bulbs. I will say, that just because a certain light color or type "should" work well, and looks good on paper, sometimes just isn't the case in real-world use, out in the field. Also, there is a pretty vast amount of differing quality L.E.D fixtures. Most of the ones that work at least fairly decent, are very high priced, although the energy consumption if far less. Some lights "look" bright, sometimes even blinding, when you look towards them, yet the area they are lighting is dim and has very little light "saturation" (at least that's the best way I can describe it). The "best" in my personal opinion, is metal-halide because of the almost pure white light they emit, and the phenomenal light "saturation" of the area, but they do tend to use a bit of electricity though.

Nah man, leds don't give that lone drive with AoR song feeling!

Hi I came across your videos and you have very topics. 20 minutes is too mich though. Thanks

Great video, i learned a lot of things i didn't know. I would suggest that it may be too focused on numbers and technical details, much more that i would like, and it is also too long and, in my opinion, easy to make shorter without losing the fundamental info, but its the first video that i see from your channel, and maybe it is clearly focused on more technical profiles than mine. As a photographer, i just hate the yellow color of city lights, and also i'm very sad that we can't see the night sky in big cities. Technology now offers ways to solve many of these problems, so i would love to see the implementation of new light sources

Thanks for this. Best video presentation in a while, first time watcher.

My town recently replaced the sodium lamps with LEDs, and I honestly like the color. My only complaint is they aren’t as focused on the ground and they shine in your windows too much.

An adequately lit road under low pressure sodium vapour lamps is not a scotopic vision situation, it's mesotopic, You only lose your ability to distinguish colour because sodium lamps are monochromatic. If you just add 10% full spectrum light, you can see just as well as if the entire lighting setup was full spectrum. So add a 50W halogen lamp onto every low pressure sodium street light and you'll be fine. For new installations, definitely go with LEDs they last longer and cost about the same to replace.

+MrEdrftgyuji use blackout blinds then

but bad for crime

Nothing says "safe" like drivers low-key suffering from sleep deprivation.

I love cool lighting

Cool lights for highways/trunk roads and warm lights for local roads?

More power you re: science.

Im all for saving energy in street lighting and that but I have one concern. I live on a typical UK pre 1940's brick terraced row of housing street. There are 5 street lamps spaced quite far apart, one top of street, one bottom and 3 in between, one being directly opposite my home. The height of the lights is such that the head of the lamp is only just above the height of the top of the 1st floor front bedroom windows, about 6-7 meters?? They were all sodium lamps until recently and the street was very well lit and easy on the eyes. Now they are all LED and there are very dark areas between the lamps. They light only spots of the street and cast the light forward quite angrily, ie my front room looks like I have my light on, but this is just the cold white flood of light washing into my home and it bleeds through my bedroom curtains, almost looking like dawn break, all night!. The dark areas are the biggest concern as the light spacing was good for sodium, but useless for LED as now you have light-dark-light as you walk up the street, giving some unruly would be, ample places to hide without being seen.

Did I just watch a 30 minute video on street lamps...

I think led street lights look magical!

You live by Hinsdale Illinois

0:30 that rode is literally 3 minutes away from my house.

0:30 I know that exact rode...I’ve driven down it so many damn times...

I fucking love your videos. They're so in depth and I really appreciate how much research you put into them.

So led lighting might reduce the number of crashes due to drivers falling asleep at the wheel?

Bright white light reflects off snow with blinding power.

I was thinking about something, even if the new lights do put out more light pollution and more harmful rhythm disruption. Since we don't need the lights on anywhere near as bright to get the same effect. then that does counter balance it at least somewhat. I mean if it put out 4x the amount of interference at the same brightness, but only needs to be 1/4th as bright to do the same job. well then there's really not much of an argument about those bulbs being worse as, the effective output is the same.

While leds are a great way to make roads safer, they are increasing the light polution cities are making

We just changed all the inside and outside lights to LED!!! I like the whiter lights. But it’s the big energy savings, also we can turn lights on/off in rooms from the MH bulbs as once you turn them off, it would take 15 minutes before the bulbs would light back up and it takes a little bit to get Back to full brightness. We’re a food factory. With LED, you can just turn them on/off. Every year we would have to rent a boom lift to change all the bulbs outside. After a few fail, I would have to buy enough bulbs to replace everything outside. Because if you just changed out the bad bulbs, you could have another fail in a week or a month, and then your back having to rent the boom lift once again. With the LED lights, I won’t have to worry about the lights for years!!!!! My days of having to be swapping bulbs inside and outside are pretty much over, other then some T8 bulbs up stairs where most people don’t go and are off most of the time. So we didn’t change those over. LEDs have allowed us to do thing such as having motion sensors for the freezer lights. So they pop on on their own when going inside, but after leaving, in 5 minutes of no motion, they go off. We really couldn’t do this with the large MH bulbs. So the LEDs put out more light. Whiter light, and use around half the power. They power on fast and can turn on/off quickly. We gave better lighting outside now. They are maintenance free. That’s a savings in labor. Savings from having to rent a boom lift. The pros way, way, way outweigh the few cons. Which is not much of a con.

Why do we continue to put lights so high? Would not low (below driver eye-line, say 0.5m, for example) and more closely spaced be more efficient, even if you have far more of them per km of road? You only need to light the edge and the centre of the road, not the whole road and the surrounding area.

LED as lights in general is very detrimental to humans and animals, sure it saves a lot of energy but it has very pronounce effect on the human mind, LED lights emit heinous amount of green light something your eyes wont notice, but its shade is very green. Green and blue lights emitted from computer screens that have WLED have shown to increase depression, it also strains your eyes. LED also discolour its surroundings because its not a perfect white, LED in general have very poor colour reproduction most super expensive high quality LED can only do 90% colour accuracy while old fashioned light bulbs will do 100% while 10% may not sound much it actually is, what does it mean? Well 100% would be what the sun gives off. Have you ever felt really shit in rooms with tube lights? Fluorescence light emit heavy green shading in its white colour just like LED, while if you ever been in a room with traditional light bulbs you felt "comfortable"? Its all in the colour reproduction of each light. The solution to the energy issue and the colour issue would be OLED light sources which produces accurate 100% colour light and has the energy efficiency of LED. I had to switch all my LED lights in my house to old school ones, there many types of them so I wont list them all, but by doing so I felt much better, I got more productive, less depressed, they consume vastly more energy but is energy that important to sacrifice your own mental well being? I say no, most people disregard the vast importance of colour accuracy in lights. We see colours for a reason, and the human mind has very powerful associations with different colours. And just because you cannot see a colour, does not mean it is not there.

I'll say I not only enjoy and prefer 6500k lighting, but I cannot stand the digusting 2700k "yellow/orange" lighting. Maybe right before going to bed. But for any application where you turn on the light to see (i.e doing work of some form), 6500k is by far the best. Why do you think hospital and laboratories use 6500k lighting?

When I was a kid, all streets had the standard low-pressure sodium lamps. They looked orange to the naked eye, but often looked red on cameras. My street still has high pressure sodium, but I have seen plenty of street lights (particularly on freeways) that look much whiter - probably LED.

What we need is RGB street lights Gamers rise up

Very infomative. I work as a Traffic Engineer for a municipal council. These are the questions that we deal with daily

Why am i watching this??

modern led car headlights its more to do with bling than safety down right dangerous

I feel less sleepy when driving late at night since I switched to LED headlights

I prefer the Led ones, but mostly because i hate the color yellow. But yes, you are more prone to get sleepy with yellow lighting, although with blue light it "burns" you

I might argue that LED lights keeping drivers from falling asleep is a good thing I for one know I have more trouble staying awake driving in town as opposed to driving on the back roads especially after a long day of work as for light pollution coming through your window thicker curtains might help but as you said with LEDs they can be focused better and prevent alot of light pollution despite being brighter

One of the plants I was working at last year I was replacing all of their HPS lights with LEDs and some of the areas I had to put them in were hanging over walkways for those I was supposed to put ones with a reflective shade so that more light was focused downward and the only light reflecting off the floor was escaping upward today all the lights are replaced and the plant has much less of a glow where as before it was pretty bright

The answer is No.

The whole circadian rhythm argument seems misplaced for roads. That's all about helping people sleep at night. Busy roads are one of the last places you want to do that. It's fine if we're talking about residential lighting, though.

I would have thought that high melanopic light content lighting highways would be good as it would also keep drivers alert by suppressing melatonin.

I have a friend who is an RC flyer hobbyist. About fifteen years ago after mastering piloting both fixed and rotary wing aircrafts, he started flying them at night with the aid of colored LEDs. High luminosity LEDs were just coming into the markets then. With the rotary wing models he would imbed different colored LEDs in each of the rotors and white LEDs on the skids aimed downward. The skid lights illuminated the ground for takeoffs and landings while the colored rotor lights enabled him to maintain proper flight orientation in pitch black flight conditions! I'm sure the neighbors might have thought they were being watched by aliens but it was just Scott having fun flying his RC helicopters after dark. He even started placing rocket motors and also Roman candle mortars onto the skids for night time Arial shows!

Moonlight is not bluish - it's most prominent in the yellow and red end of the spectrum. It appears blue courtesy of our night vision, which uses the rod cells that are most attuned to blue light. Almost everything looks blue in low light.

8:23 I laughed & was saddened by this. Wow

LED lighting is complete rubbish. On paper for men with big glasses it may look nice, but : 1) It's nasty and completely unnatural, with unknown health effects in the long run 2) Produces glaring, which actually may increase number of accidents 3) Normally manufactured in china for cheap 4) This means service life is shorter than expected 5) So, net result of carbon emissions is zero at best 6) Output reduces with working hours. So lamp rated 10k hours will be dimmer up to unusable level much shorter that this. From personal experience by using it at home. = (

The most difficult situation in traffic to me is when there's a wet asphalt. There I've noticed that the mercury vapour lamp is far inferior to a high pressure sodium - seems that the asphalt really absorbs the light at that wavelength (though this may be at least partially caused the light output of the mercury vapour lamps being lower). I assume that the 5700K LEDs might suffer of the same problem. Optimal solution might be either to have the colour temperature or the light output of the lights to adjust based on the weather conditions - but I'm not sure how expensive this would be in practice.

when using LED why not do some kind of smart lighting system... Track traffic then dim the LEDs based on where they are actually needed. if there are no moving cars then it goes dark... this would also save a lot of power on less traveled stretches of road at night. closer to home residences this should probably not be used since light changing frequently may be distracting but in industrial areas or commercial areas it would make sense i think Also the LEDs lamps can have more then one LED color.. like a RGB... so in low traffic you could use a less safe frequency (since there are fewer cars and less of a risk... keeping the skyglow down... then when traffic picks up you add some blue light to increase visibility to increase safety) road safety is half environmental factors and half psychology... and perceived safety can have motorist increasing risk because people have a variable preference for degree of risk they are willing to live with... so really some experimentation may be in order maybe even for a given road... possibly you could even throw machine learning and custom tailor lighting for various parts of roads based on what degree of danger perceived danger will have motorist behaving their best on average. with LED light with 2 different color output you could fine tune that over time... especially if you throw machine learning at it... also more speed cameras hooked into the system would make motorist behave better too. You could also have throw machine learning at detecting infractions other then speeding... like someone driving drunk or recklessly. which could go into the analysts and machine learning used to advice light settings. (outright control may be a bit to much) now if we just had self driving cars we could ban humans from driving do away with the traffic lights entirely and skip the sky glow all together and odds are road accidents would drop to near zero over night and traffic jams would likely go away too if all routes where planed programmatically. doing away with humans is always the answer! (incidentally i am joining the robots then the revolution comes and you meat bags get replaced :p)

What my experience tells me is that bright white LED headlights serve me better than street lights or the shitty yellow lights vehicles are equipped with.

Cool, this was a great video. Thanks

When we’re driving, do we want our circadian rhythms to be correct? I would think you would want it disrupted. Don’t want to fall asleep behind the wheel.

We have white LED lights on the Baltimore beltway now. They are great and all but are overwhelmingly bright. Would be great if they found a diffuser to spread the light a little better. Next issue is that many of them are already strobing, or plain don't work anymore. Also the lights in the Fort mchenry tunnel (I95) in Baltimore now has LED lights and they are borderline blinding. It's especially bad when exiting the tunnel when your eyes need time to readjust. On the bright side, sodium lamps and fixtures are probably going to be much cheaper now.

Your logic is lacking!

I'm beginning to hate white LED lights. They give off a very cold, harsh light. Sodium lights give no color information, but they're not as harsh as the visually cold LED.

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