By Patricia Daukantas

We in the optics community all know the spiel: Solid-state lighting is better than incandescent lighting because the latter wastes a log of energy as heat. But where might hot light bulbs actually be a good thing?

The answer: in traffic lights that get exposed to a lot of ice and snow. According to news reports that have appeared over the last couple of days, LED-illuminated traffic signals don’t generate enough heat to melt off the ice and snow that get stuck to the signal lenses during a storm. Such a frozen crust can make the lights difficult or impossible for motorists to see.

According to one story datelined Milwaukee (Wisconsin, U.S.A.), public-works authorities in several states are testing out possible methods of keeping LED traffic lights cleaned off: weather shields, special heating units like the ones in airport runway lights, or water-repellent coatings. But mainly, they’re resorting to good old-fashioned manual labor to clear off the ice and snow. (Remember, one of the advantages of LEDs is that they don’t have to be replaced anywhere nearly as often as incandescent bulbs.)

That news article also cites the case of a woman in Oswego, Illinois (U.S.A.), who was killed while making a left turn at an intersection where the signals were mostly covered with snow.

The red, yellow and green lights on most American traffic signals have metal hoods to help drivers see the lights even in bright sunlight. However, those hoods don’t help as much when the snow is blowing horizontally in a blizzard.

Then again, Denver (Colorado, U.S.A.), a burg that most people associate in their minds with snow and skiing, hasn’t been having much of an icing problem with its LED signals. According to the Denver Post news brief, “Denver, with its freeze-thaw cycle, is blessed with a weather pattern that prevents the energy-efficient lights from icing over for long periods.”

2009-12 December led, leds, solid-state lighting, energy, green