The lights sitting atop traffic poles on W. University Avenue, in Gainesville, FL, glow white when the stoplights below them turn red and shut off when the lights turn green.

They mystified the whole Doria family as they waited at a red light at 13th Street and W. University Avenue while driving downtown for dinner recently, and Nickie Doria wrote to Since You Asked to find out why the white lights are there.

“We were all trying to figure out their purpose,” Doria wrote to Since You Asked. “Can you shed some light?”

Phil Mann, Gainesville’s traffic operations engineer, calls them “tattle-tale lights” for their ability to alert police that someone has run a red light, no matter where the police officer happens to be situated.

The white lights are wired directly to the power supply that makes the traffic light turn red, so they turn on as soon as the red light does.

“It’s a safety issue,” Mann said. “When officers are doing red-light enforcement, they have to see both the red light and the vehicle running it, which means having to do what? Run the red light themselves. The white lights are visible from 360 degrees, so the officer can sit downstream instead.”

Mann said a Florida Department of Transportation grant in 2006 let the city install the lights at five intersections. The city chose the five intersections where the most red-light running crashes occurred: W. University Avenue and 6th Street, W. University Avenue and 13th Street, W. University Avenue and 34th Street, Archer Road and SW 34th Street, and 69th Terrace and W. Newberry Road.

Read the rest of this entry »