# LED traffic lights can't melt off snow and ice from their lens. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [February 24, 2015, 1:39pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512 "2015-02-24T13:39:30Z")\ **Posts on this page:** 16\ **Page:** 4
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [February 25, 2015, 6:01am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/61 "2015-02-25T06:01:27Z")
They use LED traffic lights in Milwaukee. I remember after the conversion started, I was out driving one snowy day and noticed that all the lights were out…then I realized that the lights weren’t out, they were just covered in snow and it wasn’t melting. It was pretty bad. Yes, you should treat it like a 4 way stop, that’s basically what people were doing, but some people do just sail right through it, the same way people sail right through non-working lights. On top of this, it’s not even that it looks like it’s not working, it almost doesn’t even look likes it’s there since everything is covered in snow. So if you’re not familiar with the area you might not even now it’s a controlled intersection. My thought was to replace the lowest light in the pole with a standard incandescent bulb in hopes that you’d still get enough heat to keep everything warm, but still have the savings of the other two bulbs. A thermostatically switched heater coil would probably be more energy efficient and longer lasting. For those that have never seen this happen, it’s not that it [looks like this](http://www.blogcdn.com/www.engadget.com/media/2009/12/17dec9iuobsegf43.jpg) and if you can sort of make it out (though that is often the case). It’s that it [looks like this](http://bloximages.chicago2.vip.townnews.com/pressofatlanticcity.com/content/tncms/assets/v3/editorial/5/b8/5b839394-15a3-11df-b10e-001cc4c002e0/5b839394-15a3-11df-b10e-001cc4c002e0.image.jpg)…you get nothing from it, it might as well be off. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 25, 2015, 8:29am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/62 "2015-02-25T08:29:01Z")
Not a new problem: As others have mentioned, there have been news articles about this problem from time to time, for several years. It seems to me there is a blatantly obvious, and trivially simple solution that has _already been in place_ in some models of traffic lights, more-or-less forever. What am I missing here? Take a good close look at [this picture](https://www.auroragov.org/cs/groups/public/documents/digitalmedia/009929.jpg) of a traffic signal. Note the shape of the sun shields surrounding the lamps. Note in particular that _they are open on the bottom_ ! This style is not new. For as long as I can remember, I’ve seen traffic signals in this style here and there. I don’t imagine that snow or ice is going to accumulate in these sun shields, even with stone-cold LED lamps. Would it? Why is it not a solution to simply install sun shields like these everywhere? Building heaters into the lamps to melt the ice seems to totally defeat the purpose of using LEDs, which is specifically to run cold and save electricity. Might as well just stick with incandescent lamps. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 25, 2015, 8:40am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/63 "2015-02-25T08:40:33Z")
Okay, I just looked at the photos that **Joey P** linked. So. Those lamps have sun shades that are open on the bottom, and they got filled with snow anyway. Now I’m wondering: Why does that happen? Are these sun shades not open _enough_ on the bottom? Could the problem be solved if the shades were more open at the bottom? Would a hybrid solution work, having heaters that don’t need to heat as much as they would with sun shields that aren’t open at the bottom? Mostly, I’m wondering why open-bottom sun shields fill with snow in the first place, and given that they do anyway, if there aren’t other simple solutions that can work with this style of sun shades. Would it work to simply have sun shades that don’t curve around the bottom even part way like those do? ---
**Author:** ![Tabby\_Cat](https://avatars.discourse-cdn.com/v4/letter/t/6a8cbe/32.png) [@Tabby\_Cat](https://boards.straightdope.com/u/Tabby_Cat)\ **Post date:** [February 25, 2015, 9:45am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/64 "2015-02-25T09:45:18Z")
Ok, colour me puzzled. In sunny Singapore, our traffic lights look like this. [http://www.atstraffic.com.sg/images/ats\_traffic-lights-system.jpg](http://www.atstraffic.com.sg/images/ats_traffic-lights-system.jpg), they are basically open at the bottom, and I don’t think there’s physically any way of snow accumulating in front of a traffic light that had shades like this. I hardly think that anywhere in the US is getting more sun than here, especially if it’s somewhere that has enough snow to block up a traffic light. So what gives? Why the extreme sunshades? ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 25, 2015, 1:20pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/65 "2015-02-25T13:20:01Z")
> [@Senegoid](#): > > Okay, I just looked at the photos that **Joey P** linked. So. Those lamps have sun shades that are open on the bottom, and they got filled with snow anyway. Now I’m wondering: Why does that happen? > > Are these sun shades not open _enough_ on the bottom? Could the problem be solved if the shades were more open at the bottom? Would a hybrid solution work, having heaters that don’t need to heat as much as they would with sun shields that aren’t open at the bottom? I’m guessing it’s a combination of: 1. the temperature was above freezing as it started to snow 2. the traffic signal was facing into the wind, and snow blew right into it, and 3. as the temperature dropped below freezing the snow that stuck to the signal and melted slightly then froze and stuck to it. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 25, 2015, 1:26pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/66 "2015-02-25T13:26:10Z")
> [@Tabby\_Cat](#): > > Ok, colour me puzzled. In sunny Singapore, our traffic lights look like this. [http://www.atstraffic.com.sg/images/ats\_traffic-lights-system.jpg](http://www.atstraffic.com.sg/images/ats_traffic-lights-system.jpg), they are basically open at the bottom, and I don’t think there’s physically any way of snow accumulating in front of a traffic light that had shades like this. > > I hardly think that anywhere in the US is getting more sun than here, especially if it’s somewhere that has enough snow to block up a traffic light. So what gives? Why the extreme sunshades? those are available here (typically called “baseball cap” visors") but the “tunnel” style is more common because it makes the signal lights more visible in bright ambient light. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [February 25, 2015, 1:53pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/67 "2015-02-25T13:53:33Z")
> [@Joey\_P](#): > > They use LED traffic lights in Milwaukee. I remember after the conversion started, I was out driving one snowy day and noticed that all the lights were out…then I realized that the lights weren’t out, they were just covered in snow and it wasn’t melting. It was pretty bad. Yes, you should treat it like a 4 way stop, that’s basically what people were doing, but some people do just sail right through it, the same way people sail right through non-working lights. On top of this, it’s not even that it looks like it’s not working, it almost doesn’t even look likes it’s there since everything is covered in snow. So if you’re not familiar with the area you might not even now it’s a controlled intersection. > > My thought was to replace the lowest light in the pole with a standard incandescent bulb in hopes that you’d still get enough heat to keep everything warm, but still have the savings of the other two bulbs. A thermostatically switched heater coil would probably be more energy efficient and longer lasting. > > For those that have never seen this happen, it’s not that it [looks like this](http://www.blogcdn.com/www.engadget.com/media/2009/12/17dec9iuobsegf43.jpg) and if you can sort of make it out (though that is often the case). It’s that it [looks like this](http://bloximages.chicago2.vip.townnews.com/pressofatlanticcity.com/content/tncms/assets/v3/editorial/5/b8/5b839394-15a3-11df-b10e-001cc4c002e0/5b839394-15a3-11df-b10e-001cc4c002e0.image.jpg)…you get nothing from it, it might as well be off. Very illustrative photos. Thanks JoeyP. ---
**Author:** ![Mdcastle](https://avatars.discourse-cdn.com/v4/letter/m/958977/32.png) [@Mdcastle](https://boards.straightdope.com/u/Mdcastle)\ **Post date:** [February 25, 2015, 2:27pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/68 "2015-02-25T14:27:19Z")
Note in the photos the snow is even sticking to the totally flat sign. ---
**Author:** ![jz78817](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jz78817/32/1028_2.png) [@jz78817](https://boards.straightdope.com/u/jz78817)\ **Post date:** [February 25, 2015, 2:29pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/69 "2015-02-25T14:29:25Z")
> [@Mdcastle](#): > > Note in the photos the snow is even sticking to the totally flat sign. clearly, we need incandescent stop signs. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 2:44pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/70 "2015-02-25T14:44:31Z")
Driven, even slightly wet snow will stick to all kinds of things. It kind of amazes me how many critical highway signs I drive by that read things like \*\*MAX SPEED \*\*[snowblur] **5** , or even critical warning and directional signs. Seems like in all that plowing and followup berm-trimming, the right-hand guy could reach out with a squeegee and clear the signs off. I also notice that big-ass pickup trucks, which here tend to be less custom than factory “show 'em what big balls you have” models, tend to collect tightly packed snow… over the rear license plate. Funny how that is. ---
**Author:** ![aceplace57](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/aceplace57/32/3500_2.png) [@aceplace57](https://boards.straightdope.com/u/aceplace57)\ **Post date:** [February 25, 2015, 6:56pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/71 "2015-02-25T18:56:02Z")
Drivers have always counted on traffic signals being visible. Even in bad conditions. Slipping all over the road. You could still count on the traffic lights. Assuming of course it is still possible to stop. 😃 thanks to the wonders of modern tech that’s no longer true. ---
**Author:** ![Amateur\_Barbarian](https://avatars.discourse-cdn.com/v4/letter/a/59ef9b/32.png) [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)\ **Post date:** [February 25, 2015, 7:19pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/72 "2015-02-25T19:19:31Z")
> [@aceplace57](#): > > thanks to the wonders of modern tech that’s no longer true. I really can’t see this as one of the major tech crises of 2015. 🙂 ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [February 25, 2015, 7:59pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/73 "2015-02-25T19:59:54Z")
> [@aceplace57](#): > > thanks to the wonders of modern tech that’s no longer true. 1. Burnt out bulbs also suck 2. In snowy Boston, I’ve never seen this problem and most of the towns around here seem to have switched to LEDs So, a mostly non-problem, and you’re ignoring all the advantages. ---
**Author:** ![Patch](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Patch](https://boards.straightdope.com/u/Patch)\ **Post date:** [February 27, 2015, 5:00am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/74 "2015-02-27T05:00:48Z")
> [@jz78817](#): > > is this really a problem which needs solving? we get plenty of snow where I live and I’ve never seen any of the LED traffic signals get a build up of enough to block the light. Pretty much every signal I’ve encountered uses an open bottom or “baseball cap” style of visor, so snow shouldn’t be building up in front of the lens. We’ve seen one fatal from it where a driver ran an intersection because the lights were obscured. As I recall, the open bottom visors appeared afterwards when the LED issue became known. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [February 27, 2015, 5:25am UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/75 "2015-02-27T05:25:15Z")
> [@Telemark](#): > > 1. In snowy Boston, I’ve never seen this problem and most of the towns around here seem to have switched to LEDs The proper response to this remark would be to ask the obvious question: So what is the City of Boston doing right here? Have they installed heaters in their LED traffic lights? Open-bottom shades? Hot steam pipes built into each lamp? > [@Patch](#): > > We’ve seen one fatal from it where a driver ran an intersection because the lights were obscured. As I recall, the open bottom visors appeared afterwards when the LED issue became known. As we’ve now learned from Posts #61 through #65, open-bottom shades isn’t the solution. Whoda thunk? ---
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [February 27, 2015, 12:28pm UTC](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512/76 "2015-02-27T12:28:40Z")
> [@Senegoid](#): > > The proper response to this remark would be to ask the obvious question: So what is the City of Boston doing right here? Have they installed heaters in their LED traffic lights? Open-bottom shades? Hot steam pipes built into each lamp? There’s no mention of any issues or solutions - [Taking care of Boston's streetlights | Boston.gov](http://www.cityofboston.gov/publicworks/lighting/led.asp) Here’s an article from [boston.com](http://boston.com) but looks like it was written elsewhere and 6 years ago - [http://www.boston.com/news/nation/articles/2009/12/15/energy\_efficient\_traffic\_lights\_cant\_melt\_snow/](http://www.boston.com/news/nation/articles/2009/12/15/energy_efficient_traffic_lights_cant_melt_snow/) Clearly it’s a problem, but the vented shades seem to have solved most of the issues. > [@](#): > > In Minnesota, where authorities have upgraded hundreds of traffic lights to LEDs, the Transportation Department occasionally gets reports of an obstructed light. But by the time a highway crew arrives, the wind has often knocked out the snow and ice, said traffic systems specialist Jerry Kotzenmacher. Minnesota is experimenting with weather shields. [Previous page](https://boards.straightdope.com/t/led-traffic-lights-cant-melt-off-snow-and-ice-from-their-lens/713512.md?page=3)