In my area they are starting to install LED lights on the traffic lights. They are bright, use less energy, and last longer. I have seen these at more than a dozen intersections and every time they use them only for the green lights. The red and yellow are still conventional.
Any idea why?
All three are replaced with LED units in the few examples I’ve seen here in the UK.
That’s not much help, is it?
Sorry.
Perhaps they’re much more expensive, so they’re just starting with the lights that are on the longest?
When I lived in California, they had replaced the red lights only. They didn’t have LED lights for the other colors yet, I think (or maybe they were too expensive). Maybe they already have LEDs for the red, but have a plastic cover to make it look the same as the other lights, and now they’re retrofitting the green lights. Just a WAG.
I’ve seen both red and green. Haven’t noticed any yellows, though. I love them. I sometimes have trouble distinguishing the colors on those older faded lights. :eek:
Best guess: city budgets.
Here in Olympia, only the greens were replaced, and only on the busiest intersections–and, in fact, only in the directions where the light is more often green. The changed lights are in the east-west directions of a busy arterial with a side street leading to a semi-industrial area (namely, a cannery). At least in Olympia, perhaps the city crews grew tired of having to bestir themselves to stop traffic at these intersections to change light bulbs.
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How can you tell the difference?
I knew there was something different about these new lights. I was trying to tell my friends that they are LEDs, but none of them can seem to notice a difference.
Anyway… Here where I live, the Red lights were replaced first, and I am now seeing some green LEDs. I have yet to see a single yellow, though…
LilShieste
There are yellow LED signals, and I found California’s purchasing specs for 'em, but I guess that replacing the yellow lights is a low priority. I have seen newly installed traffic lights that are all LED.
My understanding is that ALL the leds are green, and that the red and yellow lamps just have colored filters.
Of course, I could be completely wrong about this.
Not all the LED’s are green. The biggest chalenge is to create a white LED. The closest they have come to is a blue one w/ a corrective lens but it still has a blue tinge.
Red LEDs are the brightest and have been around longest, and I’ve seen more of them than the others. Green and Yellow are relatively recent additions, and are both more expensive and require more voltage. I haven’t seen any yellow LED traffic lights, but they ught to exist, and many o you have seen them. The real challenge has been a good, bright blue LED, but they have hoe now, too.
I don’t think a white LED is that tough. I have one sitting on my dresser, and it’s not bad. LEDs are very nearly monochromatic, so you have to combine two or three to get a “white” LED.
In the DC area, I’ve noticed the LED lights only in Fairfax, Loudoun, and Prince William Counties, Virginia. Only greens have been installed, except for one yellow, which I cannot recall its location.
Yellow traffic lights are on so little that they outlast the red and green by quite a bit. So there’s less need to replace them with LEDs.
I’ve seen LEDs as tail/break lights on buses and letter carrier vehicles, and I’ve seen them as third break lights on ordinary cars, but I’ve never seen them as the regular tail/break lights on cars. Does any manufacturer make cars with them?
I imagine you can get third party tail LED tail lights, but it’s likely you will make your car violate the law by doing so. It’s required that all vehicles have red reflectors on the rear and the lenses of tail lights serve that purpose. If you replace your tail lights with LEDs that don’t have a lens, it wil be out of compliance. The vehicles I’ve seen with them all have other reflectors.
Some of the pricier autos have red LED taillights (a few caddies and Benzes come to mind)
THere are aftermarket led taillights that just replace the bulb so the reflector is still there.
Wonder how they will incorporate the strobe effect that certain ‘critical-location’ traffic lights have around here (in the red lens).
I believe the cities are letting the existing lights run out, and replacing them with LCDs when it’s time for a change. No need in replacing a perfectly-working light bulb, is there?
The red/green dichotomy is probably just due to which color bulb dies first. Yellow bulbs will probably be replaced last, because they’re not on as long as the red/green ones, and therefore will last longer.
Red and green are on more than yellow, but you don’t mean to imply that green is on more than red, do you? That would lead to a lot of traffic accidents.
While the yellow lights undoubtedly spend less time on than the reds and greens, would that necessarily cause them to last longer? With most incandescent bulbs, the more relevant factor seems to be how often they’re turned on and off, and that’s the same for all three colors.
I’m not sure, by the way, if they actually use yellow LEDs for the lights. Since they have red and green LEDs anyway, they can just combine them in the fixture, with some sort of dispersive lens to mix the light.