A study by the Insurance Institute for Highway Safety says cameras that help catch drivers who run red lights may also prevent collisions.

Red light cameras, used in 40-plus cities in the U.S., are triggered when someone runs a red light. The camera takes a photo of the license plate, and the owner of the car is sent a citation. Some truckers have complained that because of the length of their rigs and the shortness of some yellow lights, they could enter the intersection just as the light is turning yellow and be nabbed by a red-light camera unfairly.
The study focused on Oxnard, Calif., which installed cameras at 11 of its 125 intersections in 1997. The study found the number of collisions in the city went down 7 percent, and crashes resulting in injuries dropped 29 percent. Front-into-side collisions, the crash type most closely associated with red light running, dropped 32 percent overall, and those with injuries 68 percent.
An earlier study by the institute found that red light running dropped by about 40 percent in Oxnard and in Fairfax, Va., after camera enforcement began.
"These results represent more than a single city's success story," says the institute. "They represent solid evidence that red light camera enforcement will reduce crashes at U.S. intersections. Earlier studies showed that cameras reduce the offense of red light running by about 40 percent. But except for a few studies conducted in Australia, there had been little research on how the reduced numbers of violations translated into fewer crashes."
The institute notes that the number of violations dropped at intersections both with and without the cameras. "This has changed the way drivers behave with regard to red light running, and now we can document how this behavior change is reducing crashes and injuries," said the institute's senior transportation engineer, Richard Retting.
Nine states (California, Colorado, Delaware, Hawaii, Maryland, New York, North Carolina, Oregon, and Virginia) and the District of Columbia have laws either granting the use of cameras statewide or allowing them in specific communities.