# LED Streetlight study



## MX421 (Jun 21, 2016)

Saw this article and thought i'd share:
http://www.cnn.com/2016/06/21/health/led-streetlights-ama/index.html

Perhaps you guys might be interested in the read. Through this forum, i recently have been more educated on the LED temperatures and it was good to see this study and its results. I've been recently turning towards my warmer flashlights and its good to see the results of this study line up with my preferences....


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## jtr1962 (Jun 21, 2016)

The article isn't about a study. Rather it's about an AMA policy statement. They're confusing legitimate issues of light distribution, like glare or light trespass, with color temperature and blue content. And they're advocating for low CCT which is actually dangerously bad, just like the HPS lights it's replacing. Many studies have been done on visual acuity versus color temperature. Here are a few:

http://www.naturalux.com/High Color Temperature Lighting School Children_Highlighted.pdf

https://www.researchgate.net/public...he_Color_Temperature_of_the_Surround_Lighting

You want higher CCTs for streetlighting to improve visual acuity, depth perception, and peripheral vision. Most of the problems people have had with LED streetlights really come down to poor design which causes glare and/or light trespass. These issues will still exist with lower CCT streetlights of the same design. The optimal CCT for streetlights to maximize visual acuity and minimize glare is in the range of 4000K to 5000K. The "less than 3000K" they're advocating is really, really bad.

Even worse, they're getting into the blue light pseudoscience of melatonin suppression. The AMA really has no business sticking its nose into a matter like this. Streetlight design is solely the prevue of lighting and traffic engineers. The primary purpose of streetlighting is for street users to be able to see well. All other concerns are secondary other than issues of glare which prevent road users from seeing. If there's light trespass people can put up shades if it's a problem, or ask their municipality to put up shields to reduce light trespass into their residences. Beyond that, there aren't any other concerns. Whether or not the light disrupts sleep cycles for those on the street is moot. In fact, it's good if it does because it keeps drivers more awake and alert, which is exactly what we want.

I'm old enough to remember similar complaints back when we switched from mercury vapor in the 1970s to HPS. That's all we have here-the usual complaints from people about something new.


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## MX421 (Jun 22, 2016)

Well, they supposedly did a study. I agree though, the AMA has been sticking their nose into quite a few areas that aren't any of their business. Recently they got into gun control as well....lol. Still, i thought the warmer light preference was pretty interesting as i have been getting into warmer tints recently.


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## jtr1962 (Jun 22, 2016)

MX421 said:


> Well, they supposedly did a study. I agree though, the AMA has been sticking their nose into quite a few areas that aren't any of their business. Recently they got into gun control as well....lol. Still, i thought the warmer light preference was pretty interesting as i have been getting into warmer tints recently.


Lots of people here are into warmer tints and/or high CRI. To some extent it's an aesthetic preference. In some cases a warmer tint allows you to better distinguish colors of a scene which has mostly reds and oranges. Streetlighting is a unique case where studies pretty much point to 4000K to 5000K (a range which qualifies as neutral white) being optimal given the typical colors in a street scene, plus the importance of contrast, depth perception, and peripheral vision over any aesthetic or color rendering concerns.

I wasn't aware the AMA had gotten into gun control recently. Ugh.


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## Subterrestrial (Jul 27, 2016)

Interesting. They switched over to LED streetlights in my town about a year ago. They must be below 3000K, because I go walking at night a lot and haven't really observed any noticeable adverse affects. There is the obvious (albeit barely noticeable) hint of blue that comes with cool white LED lighting and it's especially noticeable when you compare it with the warm white lighting people have in and on the outside of their houses, but it's not obnoxious. 

One of the things I like most about it is that it attracts a lot more insects, which in turn attracts bats, which makes for some interesting night time encounters. I definitely like them more than the old sodium pressure streetlights (though I already feel kind of nostalgic for them).


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## recDNA (Oct 3, 2016)

Check out @CNN's Tweet: https://twitter.com/CNN/status/782981041078300673?s=09


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## idleprocess (Oct 3, 2016)

jtr1962 said:


> Lots of people here are into warmer tints and/or high CRI. To some extent it's an aesthetic preference. In some cases a warmer tint allows you to better distinguish colors of a scene which has mostly reds and oranges. Streetlighting is a unique case where studies pretty much point to 4000K to 5000K (a range which qualifies as neutral white) being optimal given the typical colors in a street scene, plus the importance of contrast, depth perception, and peripheral vision over any aesthetic or color rendering concerns.
> 
> I wasn't aware the AMA had gotten into gun control recently. Ugh.


People will complain about things that simply don't matter. I replaced the floodlamp fixture over my driveway with 4000K LED's and installed a porch light with a 5000K bulb. This annoyed my neighbor with their extensive halogen landscape lighting with color temperatures rivaling high pressure sodium, but there's no HOA to complain to about lack of conformity to their aesthetic sensibilities.

If high blue content is causing _actual_ disruption to the live of citizens or wildlife it's worth examining. Anectodal, but I know that birds have a tendency to go freaking nuts at all hours in areas with metal halide lighting - perhaps related to the increased blue spectrum vs HPS? I was a small child when I last lived in a community with mercury vapor lamps - and there were neither mockingbirds nor blue jays in coastal Oregon - so I can't say whether they had the same effect as metal halide or LED.

The local 7-11s have replaced all of their outdoor lighting with LED - light standards, bay lighting over gas pumps, building perimeter lighting - and it's almost indistinguishable from the combination of metal halide and floro they used to sport.

The AMA would do well to look after its own house prior to opining on external factors; medical malpractice _(or rather "preventable medical errors")_ rank quite high as a cause of non-natural deaths and disabilities.


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## iamlucky13 (Oct 19, 2016)

I know this particular post is somewhat old, but the topic is still relevant.



jtr1962 said:


> And they're advocating for low CCT which is actually dangerously bad, just like the HPS lights it's replacing. Many studies have been done on visual acuity versus color temperature. Here are a few:



No, a 2700-3000K, 75+ CRI street light is not "just like" a 2200K, 20 CRI HPS street light, nor is it "really, really bad." It's a huge improvement over HPS lights. At worst, ~3000K is only slightly worse than ~5000K, and are far more similar to each other than HPS is to either, but the small differences in acuity and depth perception aren't the only factors at play.

And those studies you linked are only of black and white, static subjects under flat lighting, and at least 10 lux light levels. No glare, no truly low light levels, and no real concern about preserving night vision - to be clear, 10 lux is a minimum goal for a streetlighted area, but the level will be far lower as you leave the lit area.

Proper shielding most certainly does help (and improves efficiency by reflecting light where it is needed), and is part of the AMA recommendation. Yet even well shielded and aimed fixtures still produce some spill and glare. The only way to effectively avoid glare is to increase the lighting angle, which means either significantly increasing pole heights or spacing lights significantly closer together so their beams can be narrowed. Neither option is very practical. Reducing CCT, however, is.

There was unsurprisingly quite a bit of discussion among those involved in street lighting decisions following the AMA policy statement, and one of the ensuing comments that sounded sensible to me was from the city of Phoenix. They indicated their plan was higher CCT lighting along busy streets and in commercial/industrial areas, and lower CCT lighting along less busy residential streets.



> The AMA really has no business sticking its nose into a matter like this. Streetlight design is solely the prevue of lighting and traffic engineers.



If only the real world could be so handily isolated to intended consequences. You might as well say the AMA has no business sticking it's nose into air pollution either - that's solely the purview of automotive engineers.

Trying to dismiss blue light melatonin suppression as pseudoscience isn't helping argument. Are you perhaps thinking instead of blue light hazard? There is also real concern about blue light retinal damage, but only at very high intensities (staring directly at a bare, undiffused emitter for an extended period of time is one case I've seen referenced. Welding is another). Concerns about blue light hazards from conventional lights does indeed sound like pseudoscience.



> I'm old enough to remember similar complaints back when we switched from mercury vapor in the 1970s to HPS. That's all we have here-the usual complaints from people about something new.



The AMA publishing a policy statement based on a review of multiple avenues of ongoing research is a very different situation from people with no expertise at all complaining that things are different than they're used to.


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## ssanasisredna (Oct 25, 2016)

Actually I would say this is mainly a case of the AMA trying to appear relevant.

1) They are not experts in what constitutes effective lighting.

2) They are not experts in the glare and the differences become discomfort glare and disability glare (I would say obviously).

3) They are not really even experts in the comparative impacts of "blue" light given that is generally the purvey of scientists and researchers who are not members of the AMA.

Starting with common sense, most people who are at any point in time exposed to street lights would, if not driving, be in a lit indoor environment that while likely lit with low CCT bulbs, would be lit with vastly higher levels of light.

- Taking this last statement into account, discussing retinal damage w.r.t. street lights is of course a non starter. The exposure levels/time are inconsequential compared to daily exposure.

Starting also with common sense, I want people driving to be as awake as possible .... hence some blue is not a bad thing and likely a good thing for alertness by suppressing melatonin.

"TO BE CLEAR" --- 10 lux IS NOT the minimum goal for a street lighted area. It can be higher, and it can be lower. It all depends on the traffic level, potential for pedestrian conflict, etc. High use urban can be that high, lots of other roads are lower.

Again on to the "not the AMA's purvey", for high speed roads, there are good engineering/science arguments that there is little value in high CCT light sources since you are almost exclusively using central vision. They were right almost by accident.

In low speed areas, there are very good arguments that higher CCT contribute to much faster and more effective peripheral vision. Of course, you don't need 10 lux for that.

The AMA policy statement for the most part was, to me, not a great review of multiple avenues of research and to me, seemed narrow, missed critical elements and frankly missed common sense.


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## KXA (Oct 27, 2016)

In my home town, they were replacing the HPS lumenaires with 4000K LED lumenaires. Because of the AMA, (and other studies) they have put the project on hold and have decided to replace everything with 3000K LED lumenaires. I can see why the interest. The lumenaires that were being installed were quite glaring, not because of the color, but because of the optics. The project won't resume until 2017. It will be interesting to see how this turns out.


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## mntbighker (Oct 27, 2016)

I would be very curious to see how bad any of the LED lamps work in heavy fog compared to HPS. In the CA central valley the HPS lamps used to cut through the fog like a hot knife at times when my halogen headlights were totally useless. The LED's going in here in Silicon Valley seem to me like they will be useless in heavy fog.


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## ssanasisredna (Nov 11, 2016)

They cut through because they are above you, not because of the color.


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