US Streetlights Are Turning Purple • Hacker News Board

Re: US Streetlights Are Turning Purple

#61

Post by neilv » Wed, Jun 18, 2025, 12:16 AM UTC

As someone who walks a lot (including, for many years, back late at night from work or school), I really wish they'd made the LED streetlights approximate the original warm color temperature from the start.

Instead of going bright white, high-color-rendition, wake-up-and-kiss-your-sleep-schedule-goodbye, which is what they went with instead.

When the LED streetlights were first installed, they were horrible, and we were promised they would be adjusted, but they never were sufficiently.

Maybe caring about the look of neighborhoods, and the sleep of people who walk or have unfortunate bedroom window positions, would've had a side effect of avoiding the problem in the article?

Re: US Streetlights Are Turning Purple

#62

Post by hollerith » Wed, Jun 18, 2025, 12:23 AM UTC

neilv wrote: post #61

As someone who walks a lot (including, for many years, back late at night from work or school), I really wish they'd made the LED streetlights approximate the original warm color temperature from the start. Instead of going bright white, high-color-rendition, wake-up-and-kiss-your-sleep-schedule-goodbye, which is what they went with instead. When the LED streetlights were first installed, they were horrible, and we w…

I've started wearing blue blockers when going out at night.

Re: US Streetlights Are Turning Purple

#63

Post by jamiek88 » Wed, Jun 18, 2025, 12:24 AM UTC

cogman10 wrote: post #47

msgodel wrote: post #44

Earlier quoted context omitted.

I was told it was to make it hard for people using needles to find their vanes. It turns out it's just the phosphor coating coming apart. The LEDs used to energize that to make the broad spectrum light are usually blueish purple for maximum efficiency.

It does do that and it's used for that. I first experienced that in a bathroom in England. Door open, regular white light. Lock the door, blue light. I thought I broke something when that happened.

Makes the cocaine easier I see too! Social economic apartheid for the win!

Re: US Streetlights Are Turning Purple

#64

Post by neilv » Wed, Jun 18, 2025, 12:28 AM UTC

hollerith wrote: post #62

neilv wrote: post #61

As someone who walks a lot (including, for many years, back late at night from work or school), I really wish they'd made the LED streetlights approximate the original warm color temperature from the start. Instead of going bright white, high-color-rendition, wake-up-and-kiss-your-sleep-schedule-goodbye, which is what they went with instead. When the LED streetlights were first installed, they were horrible, and we w…

I've started wearing blue blockers when going out at night.

Which is why this part of the article was the frustrating icing on top:

> One thing that Bullough suggests pedestrians and drivers do to stay safe under purple streetlights—or any lights, for that matter—is to remove sunglasses and blue-light-filtering glasses when walking or driving at night.

Re: US Streetlights Are Turning Purple

#65

Post by cootsnuck » Wed, Jun 18, 2025, 12:41 AM UTC

There's multiple adjacent parking lots in my city that are full of street lights that emit blue light. I've been wondering for awhile why in the world they would be blue but I think I got my answer. Probably someone trying to cut costs a bit too aggressively. My city and state are known for skimping on anything and everything when it comes to streets and roads.

Re: US Streetlights Are Turning Purple

#66

Post by bertm » Wed, Jun 18, 2025, 12:42 AM UTC

A friend and I found a contractor to give us a couple of these lights in the Phoenix area. We traced the LEDs back to a Seoul Semiconductor Phosphor on-chip design. We still have a suspicion that LM80 testing didn’t catch this and it was due to a thermal cycling failure. https://m.youtube.com/watch?v=4Mll-YDDAF4

Re: US Streetlights Are Turning Purple

#67

Post by SoftTalker » Wed, Jun 18, 2025, 12:45 AM UTC

_zagj wrote: post #46

CalRobert wrote: post #5

“ producing light that is comparable or better in quality.” They don’t support this claim about led’s, and many groups are concerned about harsh cool light interrupting circadian rhythms. They’re also hideous.

LED headlights are much bigger problem. Way too bright, way too blue.

Both are problems. LEDs are terrible for white light.

Re: US Streetlights Are Turning Purple

#68

Post by Zak » Wed, Jun 18, 2025, 12:51 AM UTC

neilv wrote: post #61

As someone who walks a lot (including, for many years, back late at night from work or school), I really wish they'd made the LED streetlights approximate the original warm color temperature from the start. Instead of going bright white, high-color-rendition, wake-up-and-kiss-your-sleep-schedule-goodbye, which is what they went with instead. When the LED streetlights were first installed, they were horrible, and we w…

There are 1800K white LEDs as well as phosphor-converted amber made to approximate the look of the classic amber low-pressure sodium.

1800K white can render colors surprisingly well depending on the phosphor mix. I recently put one with claimed (and measured) CRI over 90 into a flashlight and was surprised to see that it actually can render blues reasonably well.

I'm inclined to think those are better choices for street lights than anything daylight-ish, but I also think we should use far fewer street lights. Their presence often reduces the contrast car headlights provide, making it harder to spot hazards while driving.

Re: US Streetlights Are Turning Purple

#69

Post by Zak » Wed, Jun 18, 2025, 1:03 AM UTC

Sunspark wrote: post #45

quickthrowman wrote: post #22

Earlier quoted context omitted.

LED fixtures with a high CRI (90+), a proper lumen package, and color temperature are indistinguishable from incandescent lights. Unfortunately, most pole lights are 70CRI, too bright, and the light is too white (4000K+).

The wavelengths are spiky compared to incandescent, and the LEDs flicker if they are not DC-driven. The flicker is pretty annoying because the transition is an abrupt on-off. Where I am the city had the bright idea to wrap LED ribbons around the poles in the downtown area to make it look more interesting. They connected the ribbons without diffusers directly to the power source of the streetlight. So what has happene…

It's possible to make an LED with a spectrum that is not very spiky, which a fan of incandescent light will likely enjoy. There is a cost to efficiency, which makes LED fixtures and screw-in bulbs with those traits specialty items. A color rendering index and R9 both in the high 90s is usually enough information to pick out such light sources.

Flicker is also not a given, but a product of using cheap rather than good methods to power LEDs starting from AC mains power.

Re: US Streetlights Are Turning Purple

#70

Post by ChrisMarshallNY » Wed, Jun 18, 2025, 1:09 AM UTC

neilv wrote: post #61

As someone who walks a lot (including, for many years, back late at night from work or school), I really wish they'd made the LED streetlights approximate the original warm color temperature from the start. Instead of going bright white, high-color-rendition, wake-up-and-kiss-your-sleep-schedule-goodbye, which is what they went with instead. When the LED streetlights were first installed, they were horrible, and we w…

The main issue that I have with LED lights, is that they are very coherent, so the brights are brighter, but the darks are darker.

This can easily be seen by looking at the shadows under an LED streetlamp, compared to a metal halide one. The LED shadows are very sharp.