When used in traffic signals, the lights don't get warm enough to melt snow.
The snow obscures the signal and people die.

"Cities around the country that have installed energy-efficient traffic
lights are discovering a hazardous downside: The bulbs don't burn hot enough
to melt snow and can become crusted over in a storm - a problem blamed for
dozens of accidents and at least one death."

http://news.yahoo.com/s/ap/20091216/...red_stoplights

Some cities are considering hiring midgets to sit atop the signals with
hair-dryers and long extension cords to keep the traffic signals clear.
(Some species of monkeys could be trained to do the job, but the training
time would take too long to be effective this season.)