[HN Gopher] US Streetlights Are Turning Purple
___________________________________________________________________
US Streetlights Are Turning Purple
Author : surprisetalk
Score : 47 points
Date : 2025-06-13 15:04 UTC (4 days ago)
(HTM) web link (www.scientificamerican.com)
(TXT) w3m dump (www.scientificamerican.com)
| Simulacra wrote:
| https://archive.ph/6xm8M
| mrtksn wrote:
| Here's a video on the topic from 2 weeks ago:
| https://www.youtube.com/watch?v=Jfr8fmF8oJU
|
| Pretty interesting.
| clumsysmurf wrote:
| A Trader Joe's in Phoenix has had these for so long (years?), the
| parking lot is bathed in almost completely blue light. They don't
| seem to care. It really throws off your vision and things look
| "fuzzy".
| sidewndr46 wrote:
| Maybe it's just me but the actual color of the light never
| bothered me. The first time I saw it I figured out it was a
| form of LED failure. It's so common here that I don't think
| about it anymore
| pxndxx wrote:
| monochromatic light as emitted by LEDs is quite disorienting.
| sidewndr46 wrote:
| I grew up in the generation where every manufacturer
| decided blinding bright blue LEDs were standard features of
| all consumer electronics. Maybe I am just desensitized to
| it?
| CalRobert wrote:
| " 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 wrote:
| 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.
| hedora wrote:
| Sodium lights aren't even orange in the normal sense of the
| word. They only emit one wavelength.
| wiredfool wrote:
| I thought it was two - the sodium double emission line.
| addaon wrote:
| > 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 wrote:
| 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.
| lukas099 wrote:
| I think they mean they don't emit a "natural" orange
| (like an orange flower) that is really some kind of sum
| of many wavelengths. I could be wrong though.
| xattt wrote:
| If orange was tolerated before, I am curious why orange LEDs
| aren't being looked at again for resilience.
| looofooo0 wrote:
| Well we cannot manufacture orange LEDs with good
| efficiency.
| goku12 wrote:
| 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.
| Lammy wrote:
| > Quality LEDs are quite nice indeed
|
| This is true but irrelevant when cost reduction is the
| motivating factor for switching to LED lighting, because that
| motivation will extend to the upfront purchase cost of the
| lamps and they will buy whatever is cheapest.
| quickthrowman wrote:
| 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 wrote:
| 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.
| anonnon wrote:
| LED headlights are much bigger problem. Way too bright, way too
| blue.
| osigurdson wrote:
| TL;DR - coating is wearing off.
| xxs wrote:
| Sure, white LEDs are blue LEDs with a phosphorus layer. The
| Blue LED invention led to the 2014 Nobel Prize for Physics.
| waltbosz wrote:
| I (and my 6-year-old) really enjoyed this video from
| Veritasium about the invention of the blue LED.
| https://www.youtube.com/watch?v=AF8d72mA41M
| downboots wrote:
| The fix is incredibly simple
| https://www.youtube.com//watch?v=4Mll-YDDAF4&t=678
| ramses0 wrote:
| This should be top comment!
| echelon wrote:
| Better article with lots of pictures and diagrams, links to
| conference talks, etc:
|
| https://inside.lighting/news/24-05/heres-why-led-streetlight...
| ipdashc wrote:
| 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").
| modeless wrote:
| > 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.
| PedroBatista wrote:
| No, sodium vapor lights offer great performance in terms of
| contrast and visibility. Especially in bad weather conditions.
| robertlagrant wrote:
| Yes but that's the point: sodium vapour offers worse
| peripheral vision, so it could make some situations riskier.
| metalman wrote:
| 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
| quietbritishjim wrote:
| > once something is into your periferal vision while in a
| moving car it's too late, and fact does not matter.
|
| When you're looking up in your rear view mirror, your
| view of the road ahead is from your peripheral vision. It
| most definitely does matter.
| joshstrange wrote:
| > 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.
| neutronicus wrote:
| 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 wrote:
| 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.
| kayodelycaon wrote:
| 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.
| 1970-01-01 wrote:
| Someone did, it's accurate to state this is published work
|
| https://www.youtube.com/watch?v=4Mll-YDDAF4
| floatrock wrote:
| > 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 wrote:
| > 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.
| hoseja wrote:
| This is wrong about phosphors in the initial explanation, no?
| They are actually quite broadband AFAIK.
| RDaneel0livaw wrote:
| 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.
| padjo wrote:
| 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 wrote:
| 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 wrote:
| 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.
| davidmurdoch wrote:
| 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?
| kragen wrote:
| I haven't tried them, but they sound _awesome_.
| malfist wrote:
| 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
| guicen wrote:
| 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.
| Daisywh wrote:
| 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.
| gaborcselle wrote:
| Tldr " bright purple light suggests the phosphor layer around the
| lights has been "delaminated"--peeled off--exposing the blue LED
| light underneath, Brgoch says. Although blue LED lights are, in
| principle, deep blue in color"
| fennecfoxy wrote:
| 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.
| chasil wrote:
| "LED Filaments" are a more direct example of phosphor-coated
| blue.
|
| Most everyone has seen these now, in "Edison Bulbs" or elsewhere.
|
| https://en.wikipedia.org/wiki/LED_filament
| relwin wrote:
| My LCD TV did the same thing with a few of the backlight LEDs.
| Makes a big purplish splotch on the screen. Replaced the
| backlight strips and took the lens off of one of them and was
| surprised how small the LED is -- tiny yellow 1.5mm squares.
___________________________________________________________________
(page generated 2025-06-17 23:00 UTC)