Thanks to new LED lamps, thousands of green traffic lights in the Los Angeles area have been retrofitted to use 80 percent less electricity than in the past. The old green lights used 135-watt incandescent bulbs that lasted about a year; the new LEDs require only 17 watts and last from 10 to 15 years (however, their $65 price tag is a steep climb up from the old bulbs that sold for $2.50 each). LED lamps have lit red traffic lights for more than a decade, but they were considered too faint for green lights. The new LED lamps, made with indium gallium nitride, are actually brighter than incandescent bulbs.

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