the stop bar. Where is the detection zone?
It normally starts two feet ahead of the stop bar. Sensors are embedded in “loops” embedded in the pavement. Left turn loops are 60 feet long and those in through lanes are 20 feet long. We are also deploying a relatively new technology, video detection, in which detection zones are drawn on the background of the static video of an approach to an intersection. When the background changes due to a vehicle’s pulling into the detection zone, a signal is sent to the traffic signal controller, which causes the light to change eventually. This new video-based system uses the same size zones as the signal loops.
