US Streetlights Are Turning Purple
51 comments
·June 13, 2025modeless
PedroBatista
No, sodium vapor lights offer great performance in terms of contrast and visibility. Especially in bad weather conditions.
robertlagrant
Yes but that's the point: sodium vapour offers worse peripheral vision, so it could make some situations riskier.
metalman
no way, once something is into your periferal vision while in a moving car it's too late, and fact does not matter....unless it's moving realy realy fast, and then it's still too late so the real equation will involve all sorts of other inputs, like the coulor temp, and amount of direct vs reflected light, background light conditions, weather, and indivual perception of any given driver. *green light is the worst, as our eyes have the greatest sensitivity to it, and out night vision adaptation is to the black and white(muted coulor) light that is natural. current regulations are ancient, but there is no reason that a non opiniated solution cant be figured out and implimented
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padjo
It’s a fairly common failure it seems. Here’s it happening in Ireland:
https://www.irishtimes.com/ireland/dublin/2025/02/05/almost-...
I had someone complain to me about how it was a change made by the Green Party for bats: how ridiculous!
No, it’s just a faulty light…
msgodel
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.
cogman10
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.
mrtksn
Here's a video on the topic from 2 weeks ago: https://www.youtube.com/watch?v=Jfr8fmF8oJU
Pretty interesting.
guicen
It’s interesting how many people assume these purple lights are some kind of new design choice. But really, it’s just a side effect of the phosphor layer breaking down in the LEDs.
Makes you appreciate how tricky it is to balance cost, lifespan, and quality when you’re manufacturing millions of these for cities.
fennecfoxy
I've never seen a LED streetlight turn people where I live. Sounds like bad light design and the LED is perhaps getting too hot.
Though that said, just go and replace them as they would have had to for sodium vapour lamps they had before? And this time replace them with something that runs them at a lower temperature, especially if the environment during a summer could be hot from external temperature.
joshstrange
> And yet some streetlights have suddenly turned a jarring shade of purple. It is hard to determine the exact cause without dissecting one of the defective lights, but scientists have a hypothesis: bright purple light suggests the phosphor layer around the lights has been “delaminated”—peeled off—exposing the blue LED light underneath, Brgoch says.
What an annoying/bad article. "Here are our guesses of this when we could have actually figured it out". It's not like these are in space and hard to get to, they are on the freaking street. Get a crew out there and figure it out.
Then they go on to do a _bunch_ of handwavy "science" about blue light while not really making any point (IMHO).
> 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.
Ahh yes, for all the people that wear their sunglasses at night, I'll make sure to let Corey Hart know.
This just seems like an incredibly low-effort article with zero definite facts and enough hand waving to sprain your wrist.
kayodelycaon
I’m not sure if someone has dissected them to see what’s wrong and published the results.
Deductive reasoning points to a failure of the phosphor layer in a specific type of led.
floatrock
> Get a crew out there and figure it out.
I mean, to be fair, the city maintenance crews don't generally run tear-down youtube channels with appropriate equipment to take a close look at a failing semiconductor-based light assembly.
But the general point is correct. What could be done is connect with some of those crews' offices, understand what warranties are provided with the municipal purchase of those bulbs, and how much comes out of the infrastructure budget to do an early replacement of these bulbs. Hopefully these bulbs weren't purchased from a RANDOMSYLLABLE amazon china dropshipper who disappeared after 3 months.
But yes, that requires talking to municipal governments, and there's not enough click revenue to support that level of journalism anymore.
Maybe a youtuber who runs a tear-down channel can do that.
bob1029
> Hopefully these bulbs weren't purchased from a RANDOMSYLLABLE amazon china dropshipper who disappeared after 3 months.
This is how most LED bulbs in use today are purchased. In theory, LED is absolutely superior when engineered correctly, but it rarely is on a statistical basis when looking at the available products.
It's hard to make an incandescent bulb that is shitty, other than making it not last for a very long time. I'd rather a dead bulb than one that turns my street into a nightclub.
neutronicus
FWIW I do wear sunglasses for long highway drives at night.
Without them halogen headlights in my side mirrors give me a migraine after a while.
jessriedel
FYI you can get auto-dimming side mirrors (same mechanism as for rear-view mirrors). I presume it’s a pain to install them after-market, but it can be done and maybe worth it for you if brights bother you enough to wear sunglasses.
davidmurdoch
Read somewhere a few years ago this was a manufacturer defect and they were in the hook for replacing them all.
I've (not seriously) considered buying a pellet gun to shoot out the 4 massive neon purple lights at the entrance to my quaint 1970s era neighborhood. They didn't remove the old light poles after installing the new ones about 3 years ago, so it's double lit with sodium vapor and purple now.
Curious is there is a single person on the planet that prefers the white (er, purple) street lights?
malfist
Single wavelength light is easier to remove or filter out for astrophotography than broad-spectrum light.
But driver safety is probably way more important than my hobby
kragen
I haven't tried them, but they sound awesome.
chasil
"LED Filaments" are a more direct example of phosphor-coated blue.
Most everyone has seen these now, in "Edison Bulbs" or elsewhere.
Daisywh
To be honest, I quite like this atmosphere. Some roads near my home now feel like something out of a science fiction movie when walked on at night. Of course, traffic safety may not be good, but walking at night adds a sense of fantasy.
CalRobert
“ 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.
BorgHunter
It depends strongly on implementation. LEDs can produce white light at any color temperature and CRIs ranging from terrible to great. Quality LEDs are quite nice indeed (when they're not turning purple).
Most LED streetlights replaced sodium vapor lights, though, which produce the sickliest, most horrible orange color known to humanity. Just about any LED is an improvement over those.
goku12
Strange! I was going to say the exact opposite. I find the near-white light from LEDs very harsh and tiring to my eyes. I often end up rubbing my eyes under them. The sodium orange feels cooler and easier. The strain on my eyes is similar to daylight, but without the alertness it induces. (White LEDs actually feel worse than daylight, for some reason)
There were articles a few years back stating that the blue emissions from these LEDs were rather energetic and damaging to the retina. Conversely, some articles used to claim that red light actually improves the health of the retina. I don't know if those results were corroborated or debunked afterwards.
I know that personal beliefs and biases affect our perceptions. But such diametrically opposite experiences are surprising. I'm curious to know what everyone else experiences and any insights on this.
hedora
Sodium lights aren’t even orange in the normal sense of the word. They only emit one wavelength.
addaon
> Sodium lights aren’t even orange in the normal sense of the word. They only emit one wavelength.
It's hard to think of a more normal sense of the word "orange" than "emitting and/or reflecting predominantly wavelengths between 590 and 620 nm." I guess you could argue that sodium is close enough to that lower edge to be yellow?
looofooo0
What is the normal sense of the word? I only know the CIE standard observer to define colour and with this it is clearly in the equivalence class of orange.
wiredfool
I thought it was two - the sodium double emission line.
anonnon
LED headlights are much bigger problem. Way too bright, way too blue.
quickthrowman
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+).
Sunspark
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 happened now is that as you drive or walk you are looking directly at an unshielded flickering LED.
I still continue to install incandescent bulbs. They look better, and as I live in a cold-weather country the heat they generate is welcomed.
RDaneel0livaw
one of the biggest roads in my town has these purple lights at night, and it's very off-putting honestly. Makes it kind of hard to see things properly. I specifically avoid this road at night now because of it.
echelon
Better article with lots of pictures and diagrams, links to conference talks, etc:
https://inside.lighting/news/24-05/heres-why-led-streetlight...
ipdashc
Thank you, this has been happening near me for years now and I've seen countless news articles on it, but this is the first time someone's actually linked what looks like an authoritative source (or at least anything that goes into more detail than "the phosphor is falling off... or something").
> people driving at night may notice a moving object in their peripheral vision more quickly under bluish-white light than under yellowish-white light, [...] Gaining improved peripheral vision under blue-tinged light comes with a trade-off, however: once the moving object comes into focus, it becomes harder to see.
If we were switching away from LED to sodium vapor lamps instead of the other way around, they would have written the exact same article but in reverse, still claiming the change makes us less safe.