Traffic cameras: What are they for?
AMY REININK / Gainesville Sun | October 1 2006
Nancy Hasse was thrilled when she first noticed the cameras attached to the arms of many traffic lights in Gainesville.
She figured they were there to catch red-light runners, and hoped they would quell what she saw as a growing problem.
But then, she noticed something strange: The cameras didn't seem to be doing anything to stop the violators.
"What are these things doing, or supposed to be doing?" Hasse, 64, of Gainesville, wrote to Since You Asked. "Are they working, or only 'phantom' objects? I have not seen anyone pay much attention to them, and red-light running is alive and well in Gainesville."
There's a good reason the cameras haven't been preventing people from running red lights - they're not supposed to, city traffic engineers said.
Philip Mann, Gainesville's supervising engineer for traffic operations, said when Hasse sees what appears to be a camera in an intersection, it's either a new kind of sensor made to detect vehicles waiting in intersections or a device that detects emergency vehicles with their lights on to make the traffic light turn green when they're coming through.
Within the past couple years, Mann said the city has installed cameras on or near the arms of traffic signals at seven intersections in Alachua County to operate as a new kind of traffic sensor.
The city used to rely on traffic sensors embedded in the white stop bars at intersections, which used magnetic fields to sense vehicles waiting at red lights. The sensor would send that information to a control box near the stop light, which would change the light to green if no one was coming in the other direction.
But Mann said the sensors embedded in the road are easily damaged, and expensive and time-consuming to repair.
The new cameras send video images from the intersection to a computer processor in the control box, which is programmed to recognize whether there's a vehicle in the intersection or not based on the pixels in the video images. It then changes the light accordingly, Mann said.
Mann said the video-detection system costs about the same as the embedded sensors to install - roughly $15,000 - and is far cheaper and easier to repair when it breaks.
"Instead of digging up the road to fix it, all we have to do is buy a $200 camera," Mann said. "We said, 'Gee, it's just as cheap as the old technology, and will be, we think, more effective.' "
The sensors are only at seven Alachua County intersections so far, but Mann said they're now required at every new traffic signal built as part of a city or county project.
Mann said Hasse could also be noticing sensors for emergency vehicles, which are located at traffic lights throughout town and look a lot like cameras.
Mann said those sensors detect coded emitters on the top of emergency vehicles that are programmed to make the light turn green when an emergency vehicle has its lights on. He said they have the added benefit of making it easier for people waiting at a red light to get out of an emergency vehicle's way when it's coming through.
Either way, Mann said, the cameras and sensors aren't there to catch people running red lights, but only to help drivers waiting for them to change.
"No one needs to be worried," Mann said. "Big Brother isn't watching."
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