The Sun
Sunnyvale's Newspaper

City gets the LED out in new traffic lights

By Divya Chowdary

What was that flash of light? Did someone take a picture? Is this some sort of ploy to catch red-light runners? With the installation of the new red traffic lights at intersections throughout Sunnyvale, baffled motorists have been asking these and other questions.

Actually, the bright flash of light that quickly goes off when the traffic signal changes from yellow to red is a function of the new lighting system. This style of light, which has been installed in all of Sunnyvale's 1,650 traffic signals, is shaving thousands of dollars off the city's energy bill. According to David Vossbrink, spokesman for the city, "It's basically a win-win situation; we're saving money and also conserving energy."

The new red signals, called light emitting diodes (LEDs), have 300 small bulbs in one light as opposed to the old incandescent lightbulbs, which consisted of a single bulb behind a red shell. The old lights use large amounts of energy and must be replaced about once a year. They also require a few seconds to make the change from yellow to red.

A study conducted by the city of Sunnyvale showed that replacing the incandescent red lights with the new LEDs would increase the signals' life span to 10 years. Also, if a single LED burns out, the signal will still function properly and remain visible to drivers. In addition to preventing confusion and maintaining driver safety, it eliminates the cost associated with the emergency replacement of burned-out bulbs.

LED technology can only be applied cost-effectively to red lights, so Sunnyvale's yellow and green lights will remain as single incandescent bulbs for now. "It may be awhile until green and yellow LEDs are developed in a way that would save money," Vossbrink said.

The cost of installing the LEDs throughout Sunnyvale was $273,558. Despite this initial cost, the new lights will pay for themselves in about three years, according to Vossbrink. Since LEDs use about 32 percent less energy than the old lights, the city saves $7,100 off its monthly PG&E bill. PG&E made the installation even more lucrative by offering the city a rebate of $58,880.

Despite such benefits, what seems to grab the attention of drivers is the quick burst of light that the new signal emits. "I was stopping at a yellow, when all of a sudden, a flash of light went off before the signal turned red," exclaimed motorist Chrissy Bailey. Some confused drivers are convinced that the light is actually the flash from a camera. "I swear it was taking my picture. Well, I hope I smiled!" Bailey said.

In response to this confusion, Ray Williamson, head traffic engineer in Sunnyvale, promises that the new lights aren't some "sneaky spy unit." "It's just the way the LEDs function," he assured.

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This article appeared in the Sunnyvale Sun, April 29, 1998.
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