LED lights, gaining popularity in the trucking industry for their long life, are appearing elsewhere on the road: traffic signals.
The Los Angeles Times reported recently that light-emitting diode lamps are being used to retrofit traffic signals throughout Southern California. Using LEDs can cut power consumption in traffic signals by about 80 percent, and they last 10 times as long.

LEDs haven't been used extensively for traffic signals before now because, although amber and red LEDs have been around for a while - evident on trucks and trailers - green LED lights had engineers stymied. In the past, light from green LEDs was too faint to use in traffic signals.
The answer is something called indium gallium nitride, according to the paper. The resulting bright green LEDs are brighter than the old-fashioned incandescent lights. Some people have even complained that they're too bright.
Santa Monica has just finished retrofitting all of its red and green traffic lights, nearly 3,600 of them. (Yellow lights weren't replaced, because they only burn a few seconds at a time.) West Hollywood is converting signals at all 50 of its intersections to LED lights, and the California Department of Transportation has started work on converting 850 intersections in Los Angeles and Ventura counties.
Anaheim converted more than 3,700 red signals at 273 intersections two years ago, not waiting for the green light technology.
Los Angeles is taking the conversion slowly, starting out by replacing about half of its "Walk-Don't Walk" signs. Then it will test the technology at three intersections before going ahead. Replacing all the city's traffic signals would cost $64 million.