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.

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