http://www.businessweek.com/stories/1994-11-20/traffic-lights-that-save-on-long-green

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Traffic Lights That Save On Long Green


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TRAFFIC LIGHTS THAT SAVE ON LONG GREEN

DRIVE AROUND PHILADELphia this holiday season, and you may spot some red lights twinkling uncommonly bright. Too bad they're stop lights. Still, if the 27 intersections with redder-than-red traffic signals continue to perform as expected, local taxpayers could get a gift next year from John M. O'Connell, chief engineer of Philadelphia's Municipal Energy Office: A $25 to $50 cut in the annual electricity bill from each red light. Since Philly has some 28,000 traffic signals, the total savings in future years could top $1 million.

That's just for stoppers. When green light-emitting diodes (LEDs) as bright as their red cousins are ready, Philadelphia could pocket another $1 million in savings from energy-stingy LEDs. In addition, there would no longer be a need to replace bulbs periodically--and those savings can be even larger. And LEDs are rugged: Oregon highway engineers even hit the lights with buckshot and only knocked out 20% of them. Ray E. Deese, president of R&M Deese Inc., which makes traffic signals in Anaheim, Calif., figures green LED lights will be ready in a year or two.

Hewlett-Packard Co., a leading supplier of superbright LEDs, claims its latest recipe for LEDs doubles the output of green light. The intensity of its red, yellow, and orange LEDs already exceeds that of incandescent bulbs behind a colored lens. As the range of colored LEDs expands and increases in power, huge billboards may be painted in points of light, like an illuminated painting by Georges Seurat. Long term, HP has its sights set on LED reading lamps.EDITED BY OTIS PORT


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