There is an old saying that when the traffic signals turns green don’t go right away because someone will be driving through the intersection on a red light. Red light runners cause hundreds of deaths and tens of thousands of injuries each year. In 2009, 676 people were killed and an estimated 130,000 were injured in crashes that involved red light running. About half of the deaths in red light running crashes are pedestrians, bicyclists, and occupants in other vehicles who are hit by the red light runners.

An Insurance Institute for Highway Safety study of urban crashes found that those involving drivers who ran red lights, stop signs and other traffic controls were the most common type of crash (22 percent). Injuries occurred in 39 percent of the crashes in which motorists ran traffic controls, according to a 1995 study.

Who is a red-light runner? Anyone who enters an intersection any time after the signal light has turned red, the driver has committed a violation. An analysis of 2009 fatal red light running crashes compared the red light runners with the drivers involved in these crashes who did not run the red light. The red light runners were more likely to be under 30 and male and to have prior crashes, alcohol-impaired driving convictions, and citations for speeding and other moving violations.

Police presence to enforce the law is the key to getting people to comply with a law, but communities don't have the resources to allow police to patrol intersections as often as would be needed to ticket all motorists who run red lights. The alternative is to have cameras operating in order to reduce red light running.

Red light cameras automatically photograph vehicles whose drivers run red lights. The cameras are connected to the traffic signal and to sensors that monitor traffic flow just before the crosswalk or stop line. The system continuously monitors the traffic signal, and the camera captures any vehicle that doesn't stop during the red phase. Many red light camera programs provide motorists with grace periods of up to half a second after the light switches to red.

Depending on the particular technology, a series of photographs and/or a video clip shows the red light violator prior to entering the intersection on a red signal, as well as the vehicle's progression through the intersection. Cameras record the date, time of day, time elapsed since the beginning of the red signal, vehicle speed, and license plate. Tickets typically are mailed to owners of violating vehicles, based on a review of photographic evidence.

Cities using red light cameras include Albuquerque, Atlanta, Baltimore, Chicago, Denver, Los Angeles, New Orleans, New York City, Philadelphia, Phoenix, San Diego, San Francisco, Seattle, and Washington, DC, plus many smaller communities.