A city doesn’t have to replace every light they have all at once. They can replace the incandescents with LED when they burn out (or replace all the bulbs then.) They have to deploy the bucket truck either way. The light above my head right now has one incandescent bulb and one CFL. When one burns out, it’ll get replaced with LED or whatever the technology is then. I didn’t go running around the house throwing away perfectly good incandescent bulbs just because another technology was available. I knew they were going to burn out in a year or two anyway.
How is my place of residence relevant?
Maybe I should have added a more definite smiley, but advice on snow and ice issues from someone on the southern California coast is… interesting. 
LED technology has only been improved on in just the last few years. I can recall seeing LED bulbs in the stores even in 2010 that were extremely expensive. I happen to know because I wanted to buy them. They were ridiculously high priced.
It’s only been in the last couple years that prices have dropped. The technology may be 10 or 20 years old but it certainly wasn’t affordable. From what I’ve read the tech is improving steadily. LED’s sold today are much better and brighter than they were even in 2010.
There’s even been threads here on the dope discussing how much better LED’s are today. It won’t be long and they’ll make compact fluorescent obsolete.
I didn’t realize earlier that no retrofit was needed for the traffic lights. If they can just pop in a LED bulb in the same socket than yes, that makes it much less expensive. I have read about problems with older home fixtures and LED. Sometime the LED fails prematurely and the only solution is to buy a different fixture. Something to do with too much heat or the angle that the socket holds the bulb.
Well, yeah, but I have traveled from my place of origin and have seen snowy conditions at least a time or two. I have even designed things that had to work in cold and snowy conditions as part of my profession. 
I thought I knew about snow, too, until I was staring at six feet of it packed on my deck, shovel in hand, with a bare dent in its volume after my shoulders and arms had given out. Or driven through a city that was like a 12-foot white hedge maze. Not quite the same as a refreshing day or weekend up around Tahoe.
I had in-laws in Minnesota and visited for Christmas. I was in a blizzard in Flagstaff of all places and to drive. I spent six weeks in Korea in the dead of winter. It’s not the same as living there but I have spent time in the white stuff. Of course, all of this was in the times before LEDs.
The household LED bulbs you’re seeing are, in fact, pretty new. Getting the diodes to emit a white color close to other household bulbs took a long time, and getting the price down took more time. Colored bulbs, like red, green or yellow, have been around for much longer and are less expensive.
It’s not the green lights that are a problem, it’s the red ones. If they are snow covered, they are dim & thus not easily as recognizable as a traffic light. I’m used to seeing dim red lights ‘in the sky’ where I live, whether the tail lights of a car up a hill from me or anti-collision lights from a radio tower.
they usually replace the original bulb, socket, lens, and reflector system with an integrated LED light module:
http://www.dialight.com/Product/Category/caltrans_compliant_arrows
Maybe you should get in the habit of asking questions instead of making assumptions that validate what you already believe.
Whether LED technology is “affordable” in a particular situation depends on several factors. Yes, they (still) cost a lot more than their incandescent and CFL brethren initially, but they cost a lot less to run and they last a lot longer.
Lasting longer becomes important in situations where outages cause significant problems. You are worried about outages during snowstorms - how about outages in general? LED stopights are far more likely to be working at any given point in time than their incandescent or CFL brethren simply because they last a lot longer.
Lasting longer also becomes important when replacing a burnt-out bulb is expensive. A burned-out bulb in my bathroom takes me a minute or two to replace. A couple of workers, a bucket truck, and an hour or so to get to a failed stoplight, replace the bulb, and drive back to the station costs a fair amount of money, so to a cash-strapped municipality that’s a significant factor.
That’s been answered by several people. No need to pile on. Would like to add that Stockton has been converting to LED streetlights for at least a few years.
True. Maintenance in never sexy. If your sewage treatment plant added tertiary treatment, that wouldn’t hit the news either.
Others have mentioned the rolling changes with the regular signal bulb maintenance schedule. For safety reasons, incandescents are changed on a schedule before they burn out. One thing I like about LEDs is that they can lose a bunch of individual elements and still shine on.
I read the article expecting to see snowed up signals. What I saw were easy to see signals. Pics or it didn’t happen.
So I went looking and found this. The article has more cites as well. Only found one other pic online. It’s hard to tell if either of them are actually LEDs. The first one looks like one of these. It’s also hard to tell if the snowed over signals they mention would have been snowed over even if they weren’t LED.
From the dates, it looks like people are dealing with the issue, if it’s an issue in their area. Sometimes they give the street crews scrapers on sticks. If it’s a problem in your area, complain to City Hall and/or your Public Works Department. Check online for contact numbers and/or online request/complaint forms.
For amusement - sign
That reminds me. I’ve heard that some signal cabinets* have batteries to cover short term interruptions in electricity. Since LEDs use less power, the batteries will keep them running longer during interruptions.
Of course not all signals have battery backups.
*Speaking of not knowing, until I was checking plans, I had completely not noticed those grey boxes at intersections.
Nobody is promising that they will be-there-for-you-no-matter-what on any given February 29.
I literally looked at the date on this post, as I assumed I had wandered into a zombie thread from many years ago.
Dude. Major cities have already made the change.
Not just for traffic lights, but streetlights.
Well, I learned something today. 
What led me astray was the home LED’s that were/are so expensive. I couldn’t imagine putting thousands of them in city traffic signals. Now I have learned there were cheaper alternatives that didn’t have the white light that home consumer lighting requires.
Several posters made a valid point that labor costs a major factor. Doesn’t matter if the LED costs more to purchase because they don’t require changing as often. It’s like at my job. Maintenance will replace all the tubes in a fluorescent fixture. Changing just the bad tube would cost too much labor in the long run. If a maintenance electrician has to travel to our building (we have at least 14 multi-story buildings on campus), setup a ladder, then they want to replace all four tubes in the fixture.
Traffic signal modules cost more than white household LEDs, about $50 each if bought in quantity. Still cheaper than running incandescent lamps especially considering maintenance.
Just for fun I’ve tried household LEDs in incandescent sockets my traffic signals. They generally look bad for the same reason they’re not, in my opinion, nearly as good as incandescents for household use, the color spectrum is different (a lot more yellow relative to red, although newer LEDs, and the Cree TW series especially, are better), and the directional quality of the individual LEDs and the need for a heatsink means they don’t throw light evenly in all directions. It can look bad in a household fixture and even worse in a traffic signal.
I live in a smallish village: a few years ago the parish council installed new LED streetlights — they have 14 [?] downward facing bulbs. The light is pure and white and clear.
Better than the previous streetlights, and one million times better than the Portes de l’Enfer lighting of vile sodium lamps, orange or amber, so many terrible places in Britain are cursed with.
Bad enough that household incandescents have a cheap golden glow: the orange is worse yet.