LED traffic lights don't melt snow

Cities that installed LED traffic lights to save money are learning that the incandescent lights they got rid of had a useful purpose: their waste heat melted the snow that covered them in winter storms.

200912171217Municipalities around the country are taking different steps to keep their signals shining brightly in the face of Mother Nature. Crews in St. Paul, Minnesota, use compressed air to keep their lights clean. In Green Bay, Wisconsin, city workers brush the snow off by hand in a labor-intensive process.

Unintended Consequence of Technology: New LED traffic lights can't melt snow


    1. Snowfall can be an issue for all types of light bulbs. Incandescent bulbs could not heat the lenses either… in this case. The benefits of energy efficiency are far too important to ignore.
      Save the planet…. one LED at a time!

  1. If only we could rely on global warming to melt that snow. Stupid lower carbon footprint LEDs. [comment not checked for accuracy]

  2. Arm the traffic cops with lasers and have them melt it off. Or else build bird or bat houses into the structure and let their body heat warm it up enough.

  3. I’m sure a small electric heater could be added for cold-weather climate cities, at least on future models, which could be controlled via SCADA.

  4. C’mon people, no joking. This is a serious issue! How else are were going to get those small patches of ice just on the threshold of intersections, and where pedestrians walk, if we aren’t melting snow off of the street lights hanging directly over the roads!

    We need to get cracking on this IMMEDIATELY! Maybe we can have civil servants just take a bucket of water and throw it across the road, to freeze solid, in these areas of high-risk traffic interactions. And, actually, if we are employing people to do that, we can also have them take care of other areas that aren’t always slick with ice at the same time – such as right in front of stop signs, or perhaps in bicycle lanes!

  5. Far better that we accept a future that includes coastal flooding, violent weather and rampant tropical disease then to do the unthinkable: Put little plastic domes over the lights the prevent snow from accumulating.

    1. Oh yes, the infamous coastal floodings and tropical diseases of Wisconsin…
      Don’t MN and WI already have ‘violent’ weather (in the winter that is)?

    1. I remember that episode. Quite a few of us from the midwest have known about this for some time already.

  6. okay, mildly funny consequence. not really that difficult of a fix though.
    you have the hoods that cover the top of the light, used to shade them so they’re easier to see. now you just need to add a piece of glass sloped from the front of the hood on a steep angle back to the base of the light.or instead of glass use plastic. then the snow doesn’t stick to it because it’s not a horizontal surface.

    and done?

  7. Also, not exactly the end of the world. Traffic lights are helpful, but not a necessity. When the signals are covered you can just treat the intersection as a four way stop and proceed accordingly.

    1. Yeah, but how many people actually do that, even when the lights are out altogether? I’d estimate about 70% of people don’t stop at a light that’s out.

      Also, the trick is when lights on one side are blocked and other side isn’t – which is going to be most of the time. Then you’ve got one direction showing a solid green and the other treating it as a four-way-stop. Whoops!

      1. I had told a friend from the Minneapolis area about the post and he said he had seen it before and that that was basically how they dealt with it.

        I don’t actually have a car so my firsthand knowledge on the subject isn’t all that extensive.

  8. There was a story floating around about this a ways back that was based on this.. some random down got LED stop lights, and didn’t install the little hoods that would keep snow off the lenses. Some lady drives into the intersection, cross traffic slams into her, she dies. Lawsuits pop up and the city ends up paying out for it.

    So now that city has hoods installed on their stop lights. Based on the picture attached to this story, they don’t help much.

    It seems like a redesign of the lights could fix the problem.. put in a thermometer, make the lenses from glass, and give them a heating system similar to defrosters in rear windows from cars. If temperature is below freezing, activate the heater.

    Sure it costs more, but the lights will use less power in the summer, and only generate heat when they need it.

  9. Also, depending on WHEN the snow occurs and how bad it’s blowing, the heat doesn’t always have the time or strength to melt the stuff anyway. I’ve been in plenty of storms here in Michigan where the regular lights were covered over.

  10. My understanding is that the many LED traffic lights in the Boston area *already* have heaters built in. It’s not “OMG this problems came up and nobody solved it”, but just “someone chose the wrong product”.

  11. I wonder how the cost in terms of gasoline and man-hours (not to mention carbon) to clean the snow off the lenses compares to the savings they found in switching to LEDs.

  12. It reminds me of the comment by the Rhode Island DOT

    “Our road crews are having trouble controlling Road Ice this winter season due to our road chemicals not working properly in colder weather.”

    As opposed to the Ice that occurs at WARM temperatures?

    1. “Our road crews are having trouble controlling Road Ice this winter season due to our road chemicals not working properly in colder weather.”

      As opposed to the Ice that occurs at WARM temperatures?

      No, the Rhode island DoT had it correct. Salt and other road chemicals work by lowering the melting point of the resulting salty water. This has some drawbacks – first that it’s only *really* effective down to 25F or so, and the second that there needs to be at least a *little* water present to dissolve some of the salt to jump-start the process. Now, it doesn’t get *that* cold in Rhode Island most winters, so their ice-removal planning is almost certainly oriented to above-25F conditions. Which works fine, until they hit a winter where they have a number of storms that blast through, dumping wet snow/slush that’s immediately followed by some 10F-15F air from Canada. Then suddenly the stuff that worked at 25F and up doesn’t work anymore….

  13. The lights in Green Bay are seven years old and this was the first time they had to manually clear the snow.

  14. Those suggesting slanted shields may not live in snow-prone areas. Depending on the snow’s consistency (remember, Eskimos have 32 different words for snow) and the wind conditions, snow can stick to just about anything, and it would pile up on the shield over the lower light to obscure the one above it. A heated ring around the light would take care of it just fine.

    BTW, even old style incandescent lights can freeze over if they’re on car-responsive loops in the road and don’t change often enough. And as someone pointed out, the signs get covered, too.

  15. My understanding is that the switch to LED lights was done because they were more reliable, not because they saved energy.

  16. Interesting. Reminds me of a Green, Inc. piece on how using compact fluorescent bulbs in cold climates may actually increase greenhouse gas emissions, because the waste heat emitted from incandescents slightly reduces home heating requirements.

    1. except in the summer you’re using the energy to get rid of the heat from the incandescent bulbs. wouldn’t that equal out and it’s still a net savings?

  17. the energy saved on the LED traffic lights is probably substantial. only in the north in the winter time does the lack of heat make any difference. i like the idea of a plastic dome covering the lights to keep snow off. short of that, there could be heaters that kick in only when the air is less than a certain temperature and a snow load has been detected.

  18. I’m a bit surprised that this issue wasn’t considered in the design stage; but it seems like a minor enough issue to solve.

    Mix a few photosensors into the LED array. The brightness percieved by the photosensors will be directly related to how much of the LED emitter’s light is being reflected back by snow. If this exceeds a given threshold, turn on the little solid-state heaters until the problem goes away.

    This would add some cost to the assembly(so it would presumably not be purchased by cities in suitably warm climates); but would be substantially cheaper than manual clearing, substantially more energy efficient than incandescents, and no less reliable than the existing LED assemblies.

    1. I’m a bit surprised that this issue wasn’t considered in the design stage

      Probably because traffic lights weren’t designed to melt snow in the first place, it’s just an unintended benefit of the old design that nobody really noticed until it went away.

      Like gabrielm said at #1, the sign on the right didn’t melt the snow either.

  19. can’t we just build roundabouts and get rid of these lights all together (no light is greener even than an LED)… oh yeah, roundabouts are safer too.

  20. shMerker must live in a small enough town that “just treat them as a four way stop” doesn’t equal total gridlock. Only a fraction of the number of cars per hour can make it through a four way stop of two wide, multilane streets, because each car must wait for the car on the side street to accelerate from a stop and clear the intersection.

  21. Trust it to the right wing to turn a good thing into a bad thing when it doesn’t suit them…

    Really, all that energy, all that carbon wasted melting snow for how long? How many people were robbed, killed, forced to live and starve under brutal dictators to get that oil used to melt snow?

    And, uh, how much trouble would it be to fix this? Well, just so they can feed the construction companies and make everyone sit for a few extra hours a year, cities are always replacing good stuff that doesn’t need fixing. Get new fixtures that account for this issue. Or, just put slanted bits of plastic over it, something a “No Bid” company would do for $500 each lens, but some chemistry or engineering students could work out and have manufactured for 50cents each as little or as many.

  22. Oh PLEASE don’t suggest roundabouts in Canada…
    no one here understands them!

    Over tha last few years they’ve been cropping up in Southern Ontario but I have yet to see one done right. (Canadians seem to just not understand either how to build them OR how to use them…. when they put the first one in the area the local paper caught a municipal vehicle going the wrong way.)

    In the old days they had guys with long poles to light the lamps. Now we need guys with long poles to brush off the snow.

  23. Not sure if I buy the idea that compact florescent bulbs are causing problems because they don’t produce as much heat, but I can say that it is a slight problem with wells. Normally I’d throw a 100 watt bulb in the well house, but during my last trip to the store I couldn’t find one.

    As far as the traffic light issue I’d imagine that old surveillance cameras provide the answer, or at least their small heating coils do.

  24. LED tail lights have the same problem, in blizzard conditions they can be completely obscured, with drivers unaware that they have no visible lights on the back of their vehicle. Incandescents eventually melt enough snow to at least allow a glow to shine through, on a light car in whiteout conditions it can keep them from disappearing completely.

  25. If we put lights in a horizontal position, then there’s no snow to build up.

    Otherwise, a simple electromagnet inside the housing could shoot out a torpedo and slam against something on the inside, shaking off the snow. If that isn’t enough, then send some crews.

    Simplest way to fix this? Instead of three snouts, have just one tall & narrow one, with slats on the top. Makes for a larger signal, but solves the problem of glare and snow build up.

    Or use those insane bright LED’s that are common on bank signs. You can see those even on the brightest days.

  26. I can think of more than a few solar/battery combo options to take care of this. But, I guess we need to continue to use our tax dollars, etc. to float rich assholes running the health insurance companies, banks, auto industry, etc.

    Maybe we should just shut down all the streets except in the wealthiest areas and just bring back serfdom all the way for the rest of the country. Serfs don’t need cars. C’mon, America.. we don’t do things halfway!

    Serfdom now!!

  27. shMerker, that sounds good in theory, but it’s a recipe for disaster. For what may look like covered snow on your end might be a clear view on any of the other three ways. Your might be proceeding unwittingly through a red light by the cross traffic’s view.

    Steauengeglase, ask any kid with a 40-watt *Easy Bake Oven* who knows how hot that light bulb gets in baking their cakes. I had a friend roast a turkey using two 60-watt light bulbs in an aluminum-foil lined cardboard box. Believe me, three 67 to 115-watt incandescent traffic lights produce more than enough heat to melt snow.

  28. “If we put lights in a horizontal position, then there’s no snow to build up.”

    And then the colour blind people can’t tell if it’s red or green…

  29. I love it! Just last night I read my 5 year old an african folktale called the king and the frogs (Why Mosquitoes Buzz in People’s Ears) which teaches children about balance in nature. The traffic lights were an example from real life.

  30. I linked the article on the professional social networking site Linkedin, and then started wondering if it’s actually correct. There isn’t much evidence cited, if you read it carefully. High-power LEDs actually put out quite a bit of heat, after all, though they are more efficient than incandescent lamps. One professional commented that he’d researched it a while back in Indianapolis, Denver and Toronto (I don’t think I can cite him by name, sorry) & he didn’t think it was a common problem there, but the weather might be different in Minnesota and Wisconsin.

  31. I wonder how they didn’t see this coming? On the other hand, maybe the snow will block those nasty red-light cameras so many cities like to install.

  32. @randwolf: We were told to use HID lamps to light a big public art project by our lighting consultant. According to him, LEDs definitely don’t put out enough heat to keep up with snowfall here in Michigan.

    Re: LEDs as energy saving devices on traffic lights. Chroma is right, I think. I worked on an LED street light conversion project at one point. Street lights see decent energy savings, but IIRC, on the signals it’s all about the bulb life and its tolerance for lots of power cycles. Even with street lights, I think the reduced maintenance probably saved more than the reduced power costs. Over ten years you save 3 bulb changes and often a fixture change. It adds up fast.

  33. Just the other day I was scrutinizing traffic signals in my nabe and i noticed that the green and red signals are LED but the amber lights are incandescent. Anyone know why would this be so?

  34. I’ve noticed here in Toronto the new LED traffic light are A LOT brighter than the old ones.

    So, maybe they don’t need the cones around them that keep the sunlight off? —> Thus the snow wouldn’t collect there.

    1. The cones (or shades) are not just there to keep the sun off. They are often used to hide the lights from drivers coming from the other direction. The state of the light is hidden in this way to stop drivers pre-empting the change from ‘go’ to ‘stop’ and jumping the lights.

  35. The old style lights could be covered by snow as well after all, just in more extreme conditions.

    There is no need for a solution. There is a need for people to learn how to drive and think at the same time.

  36. Ned316, the incandescents are probably being replaced as they fail.

    Patrick, thanks. HIDs are more efficient than LEDs, though, so I’m confused. Oh, well, I suppose eventually research will sort it out. Or maybe it’s already in some obscure paper I haven’t seen.

  37. They don’t really need to sweep them off. They just need to “nudge” the pole with the snow plow. Then you get that lovely “flump” noise.

  38. I encountered this very phenomenon this morning in Plymouth, Massachusetts – “America’s Hometown!”

    I nearly drove straight through a red light – and cars were indeed approaching from either side. It would have been a mess.

  39. The trouble seems to be lack of common sense, we are being forced to give up incadescent lamps but CFls use lots more power in many conditions, the greenies just look at a blinkered view and legislate for that. The most efficient form of lighting is, according to some real world type tests, quartz lamps on dimmer switches, they are cheap tp make (in both ease and pollution) and outlast CFLs in hours. If you use a CFL in a place where it is switched off and on a lot (like a washroom) it will cost a lot in power and have very poor life, a cheap 60 watt lamp will use less power and last longer. The save the planet movement is littered with these dead bodies, the catalytic converters on modern cars, unleaded petrol.

  40. Yeah, thats really amazing. Now you just need to add a piece of glass sloped from the front of the hood on a steep angle back to the base of the light or instead of glass use plastic.

  41. This is how stimulus works. Install a green product which on the face is an investment leading to “long-term savings” (usually huge numbers are quoted), but then the other shoe drops and it ends up not saving any $$. Then the unintended consequences create work. Stimulus in action! Nice work people. Now do your taxes and pay what you owe. They need to keep this economy moving.

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