I get that they’re cheaper to operate, but they throw shadows differently and have more blue wavelengths in them (in nyc they’re 4000 kelvin last I looked). It personally feels much less magical to me and 3-4 years in I still haven’t really gotten used to it.
It also makes me feel less safe at night. I get that the orange glow makes everything look muddy, color-wise, but it doesn't kill your night vision to the same extent as the bright white LEDs do. Sure, things directly under the streetlight are lit up like it's daytime, but I can't see for @$#% in between the streetlights or behind the bushes or whatever.
I'm curious why it seems that no city has tried installing amber LEDs in an effort to try and realize the efficiency gains without quite so many of the downsides.
Flagstaff, Arizona did. There are some drawbacks, mostly that they simply don't get as bright.
https://arstechnica.com/science/2019/10/how-flagstaff-arizon...
“If you absolutely must use white LEDs, you could do what Tucson has done,” Hall said. “They... switched out their whole high-pressure sodium system to 3,000 degree white but reduced their lumen budget for street lighting from 480 million to, like, 170 million [lumens] or something. And you need to do that. For every white LED lumen, you're increasing your skyglow by a factor of about three, but they cut the lumen budget by about a factor of three. So overall, they managed to wash out the skyglow because they’ve got a lot of observatories down there.”
The extra blue is probably screwing up the circadian rhythms of humans and animals:
* https://www.health.harvard.edu/staying-healthy/blue-light-ha...
* https://www.npr.org/sections/thetwo-way/2016/06/21/482936520...
Efficiency regulations for residential fluorescent lighting delayed adoption by probably 25 years. Because regulations mandated lamps with terrible CRI.
The ideal for road safety would be more uniform lighting from a larger number of closer-spaced lamps, placed at lower height, diffused, shielded from the sides, and colored orange (and optionally uniformly dimmer).
It would also help road safety to ban the new bluer types of car headlamps, which cause much worse glare than previous yellower ones.
The color has almost nothing to do with that. Newer headlights are much brighter, and mostly use projectors now. The increase in glare is mostly due to the projectors, because they emit all their light from small point. You'll notice that newer cars with halogen projectors are almost as bad as one with HIDs.
It would be interesting to see how a headlight would look if it were able to emit the same amount of light on the road but from a rectangle spanning the entire front of the car. Minimum glare, still effective.
The color makes much of the difference. (What really matters is the total intensity in the shorter-wavelength part of the spectrum, so sure, making the lamps much brighter and less diffused is also bad.)
Shorter wavelengths cause significantly more glare, because the peripheral part of the human retina is packed with rods and S cones. Intense light including shorter wavelengths also causes the eyes to become bright-adapted, making it harder to see in the dark.
The super-bright halogen headlamps emit much more blue light than previous incandescent headlamps, and are included alongside LED headlamps in my complaint here.
Bigger, much dimmer, more diffuse lamps would help, but they should also be less blue. (And people should stop mounting headlamps on their SUVs and pickup trucks at other drivers' eye level and aiming them straight ahead.)
I have an LED desk lamp with a temperature setting, and when it's on the warmer settings it really does produce a pleasant light.
Here’s a cutsheet for a Lithonia wall pack fixture showing the different options, there’s also a chart showing what the lumens per watt is based on the color temp: https://img.acuitybrands.com/public-assets/catalog/1008038/w...
"Tunable" LEDs are just multiple LEDs, the goal being to change the emission peak. Peak wavelength can be mapped onto a black body temperature trough Wien's law (λpeak =2.8e-3/T) https://en.wikipedia.org/wiki/Wien%27s_displacement_law
I don't really know how the mapping is done, though, as there are different ways to map it since the LEDs won't have the same emission curve as a black body.
The night time lighting humans(and our non-human co-inhabitants of earth) have evolved with and known for a very longtime comes from fires of various types, flames with a much warmer color temperature.
Also, intensity is orthogonal to color temperature.
Consider the spread of lactose tolerance, a recent (no more than 10,000 years and perhaps less) mutation which has spread to 35% of humanity in that time. We have had plenty of time to co-evolve with fire, and doubtless, we have done so.
Its probably to do with cooked food, not vision - which is already co-evolved with the Sun, for when we are active/hunting/etc.
Wild animals very much do not. It's likely that our mucus membranes have also adjusted to the presence of more smoke: this doesn't prevent cancer, which is a post-reproductive problem for the most part, but it does keep smoke inhalation from being immediately debilitating.
Does it mean that fire doesn't fool our circadian rhythm into thinking it's still daytime? Sure, why wouldn't it? We've had a very long time to adjust, and getting appropriate amounts of sleep increases fitness in an obvious way.
We haven't had more than a hundred years of adjusting to bright blue-wavelength light after dark, however. So it could affect our circadian rhythm, and as studies show, it does.
Improving the lighting is also at odds with wanting a dark sky for the local wildlife too. It has a noted effect on birds for instance.
Apropos of nothing... I also remember a story about a northern country replacing traffic lights with LEDs and then spending even more money adding heaters because the old lights were naturally warm, and melted any ice that stuck to the lights. Can't find a link to it at the moment.
The Technology Connections channel on YouTube has an excellent video on this, called 'The LED Traffic Light and the Danger of "But Sometimes!"': https://www.youtube.com/watch?v=GiYO1TObNz8
I think partially the problem is people(us) have designed their lighting and safety around the street lights being on, and now they are not it is an issue. I have lived in other countries where the norm is for houses to have subtle outside lights that are permanently on at night. But around here they do not and people are more paranoid so all the terraced houses instead have over-active motion sensors with massive flood lights. That are now very noticeable when a poor late night clubber/shift worker/early morning dog walker/baker etc walks by...
https://la.curbed.com/2014/2/3/10156584/las-new-led-streetli...
I think it is neither "natural" or better illuminating. Sodium lamps have CRI of around, what, 30?
I'm glad that these sodium lamps are finally getting replaced everywhere, and cities at night won't have that monochromatic depressing-ugly-yellow lighting.
Sure what you outline is possible in some spesific scenario, but it's not gonna work for 99%
With LEDs it should be very possible to light streets with low temperature close-to-blackbody light. (I don't know if the proximity to a blackbody radiation distribution is the same as CRI etc.) Who wouldn't want this?
There are two ways of doing “white” with LEDs:
• Separate red, green, and blue, whose spectrum is spiky: https://en.wikipedia.org/wiki/Light-emitting_diode#/media/Fi...
• Phosphor, which may give you a spectrum like this: https://en.wikipedia.org/wiki/Light-emitting_diode#/media/Fi...
My city has a contact on the web, you identify the light and what you would like shaded, and they come around and block the light on that sector. In my case it looks like they painted a section of the diffuser black.
it would be neat to have light strips alongside the sidewalk and the road, as well as above. that way, the light can be lower intensity in aggregate while still providing the necessary illumination (via surrounding light vs. flooding) to make out details. our eyes are highly adaptive, and we don't need a lot of light, but rather, light from many angles.
also, the safety argument is often overstated in relation to the intensity of light. you only need a little light to reduce crime and accidents to its threshold. more isn't better in this regard.
My home city has metro coaches with either yellow or white lights. Me and a few friends of mine would skip the white ones because we found the yellow ones more comforting. On the other hand, my dad prefers white and in a room with types of lighting he will always go for the white ones.
A daylight colored bulbs are probably not doing our night vision any favors (but then head lights have the same problem, yes?). Going from a lit street onto a side street with few lights is potentially a problem depending on the kind of street lights.
More importantly, colour temperature >3200K screw up the circadian rhythms of humans and animals:
* https://www.darksky.org/our-work/lighting/lighting-for-indus...
* https://spectrum.ieee.org/green-tech/conservation/led-street...
White light reminds me of: dentist clinics, hospitals, metro stations... not very friendly places.
There's research about e.g. subway incidents and safety when they got better / brighter / whiter lights.
No affiliation, and no idea if there's truth to any of the marketing copy, but I'm personally very happy with them especially when driving at night due to the awful intensity of LED brake/tail lights on other cars.
It lit the street and not everything else.
I could see a few stars in the night sky, for the first time since moving to London.
I no longer had to deal so carefully with light leaking into my bedroom.
I've recently encountered a couple of construction sites which are illumunated by a particularly pleasant green hue at night. That might be even better.
And while we're on the subject of street lights, can we please stop with all the light pollution?
Light with more white in it feels brighter.
Drivers prefer whiter headlights because it feels like the road is more illuminated.
Car manufacturers move to HID or LED projectors for whiter light.
Whiter light causes the pupil to contract significantly more.
Drivers with contracted pupils from the white headlights find the yellow sodium bulbs in streetlights and parking lots too dim.
Governments and businesses replace the sodium bulbs with bright white LEDs.
At every step along the way we're seeing less of the night. Shadows become darker. A person or animal coming in from the shadowed roadside is increasingly invisible. A mugger can jump you from an alley with no chance of being seen because the shadows are so deep.
Now we have to increase the portion of the Earth that's illuminated at night for "safety". This disrupts animals more and deepens the shadows further.
It's incredibly stupid and there's no way to stop it without some overarching power a) doing a scientific study into night lighting and b) using that as a reason to impose intense lighting regulations and enforcement.
Too late now.
The primary effect is that its like having a near full moon effect at all times of the night. Not looking directly at the light reveals a landscape that is not harsh on the eyes but never catch a lamp straight on.
Fortunately around me the birds caught on pretty quick at first singing at odd hours until they sorted it out.
Overall its a benefit as it has opened up hours people can walk the sidewalks and even in the street without worrying about wildlife blundering into them