What are red light cameras and how do they work?

Red light cameras help communities enforce traffic laws by automatically photographing and video taping vehicles whose drivers violate red lights. A red light camera system is connected to the traffic signal and to sensors that monitor traffic flow at the crosswalk or stop line. There is constant low-resolution digital video being recorded. The system continuously monitors the traffic signal. The high-resolution still camera component is activated by any vehicle entering the intersection above a pre-established minimum speed and following a specified time after the signal has turned red. High-resolution photography is employed to capture the vehicle license plate. An additional photograph shows the red light violator in the intersection during the red phase. Cameras record the date, time of day, time elapsed since the beginning of the red signal, and vehicle speed. Tickets are sent by mail to owners of the violating vehicles, following review by trained police officers of the photographic and video evidence.