LED Traffic Lights Can’t Melt Snow: Dozens of Accidents Reported
Traffic light at an intersection in winter.
Snow obscuring the signal happens very infrequently, but nonetheless, one has to wonder where and how the ball got dropped on this, what the solution is, and whose responsibility it is to be providing it.
12/29 update: Here’s another story by the Chicago Tribune.
I follow LED news pretty closely as part of my job, but I can not understand why this story has been repeated in so many places. If you go back to the original story, this problem happened one time at one intersection during one sloppy spring snow storm on the seventh year of the installation, and the media is making this out to be an LED “problem”.
In truth, the FAA discovered this “problem” with LEDs more than five years ago when they retrofitted random LEDs into a blue runway/taxi fixture. The ice build-up problem was fixed as part of a re-design of the fixture (see http://www.lrc.rpi.edu/programs/solidstate/cr_blueTaxiway.asp).
The news in this story is that cutting corners and doing a quick and dirty retrofit of an existing light fixture does not always work with LEDs. With proper design strategies, LEDs can replace almost any traditional light source and do it much more reliably and cheaply over the long term.
This problem has gotten way too much press. If you are not sure what color the light is at an intersection that plainly has a light, why not act as if the light was out and treat it as a 4-way stop? Occassionally, the snow covers a Stop sign by my house. This logic would dictate that the DOT should install heaters on the stop sign so that I know that the 8 sided sign at the intersection, is in fact a stop sign. This retrofit is not a cheap and dirty retrofit. LEDs subjected to too much heat will have a definite life reduction. The longer life and low wattage are what makes the LED a viable retrofit. In the overall picture, how many days or hours of confusion are we talking about here as opposed to how many hours of energy savings?
Good point Dennis. I don’t have first hand knowledge of this design, but I do know of the FAA one that I cited in the first note. In that case, the LED saved something like 80% on energy, created very little heat, but the quick retrofit job channeled what heat they did create down in to the ground. The redesign used the housing as the heat sink, channeled the heat to the outside, and this was sufficient to melt the ice and still realize all of the energy savings. My point was that this could be done with traffic signals as well…
Hi, Mark and Dennis.
I agree with both the point. LED is very good solution as energy saving by way of new fixture or retrofitting. But I also understand, that LED does generate good amount of heat, A fixture should be design in such a way, that heat generated, can be diverted or used for melting snow…then such problem can be overcome.
I am from India, where LED is still in preliminary stage. but going through such discussion will give us good before hand information.
Happy New Year.
And take care…
There is a relatively easy solution which Colorado DOT has begun to incorporate. Here’s a news article on the device:
http://www.thedenverchannel.com/news/22049107/detail.html
Here’s the link to the device they’re using:
http://www.mccain-inc.com/traffic/item/signals/snow-scoop-tunnel-visor.html