Cameras watching intersections to deter drivers from running red lights may have an unwanted side effect, an increase in rear-end collisions, some studies show.
In some cases, drivers who fear they'll be caught on camera running a red light slam on the brakes, and get rear-ended by less attentive motorists behind them, studies indicate.
In Philadelphia, which is about to install the cameras at some intersections, city officials and officials at the Philadelphia Parking Authority, which will oversee the program, discounted the danger.
Any increase in rear-end collisions will be outweighed by a decrease in right-angle collisions that usually cause more serious injuries, said Charles Trainor, the city's chief traffic engineer.
``Would you rather somebody bump you in the rear, or would you rather somebody enter your driver's compartment at 40 miles per hour? That's a no-brainer,'' said Maury Hannigan, a vice president of Affiliated Computer Services, of Dallas, a bidder to install the Philadelphia system. A company is expected to be announced this week.
A 2001 study commissioned by city officials in Charlotte, N.C., indicated rear-end crashes went up by 16 percent over a three-year period after cameras were installed in 1998.
The rate of rear-end collisions increased by 37 percent in San Diego, according to a 2002 study commissioned by that city.
The camera flash can make matters worse, said Lon Anderson, of AAA Mid-Atlantic, who supports red-light cameras as long as they are used for safety rather than revenue collection.
``People see these strobes go off and realize they have just run a light, and they slam on the brakes,'' Anderson told The Philadelphia Inquirer for Sunday's editions.
Opponents of the cameras cite the studies as reason to call off the stoplight surveillance.
``What the cameras do is they change reasonable behavior into unreasonable behavior,'' said Greg Mauz, a member of the National Motorists Association, a group seeking a ban on red light cameras.
John Petrozza, president of Mulvihill Intelligent Control Systems Inc., which has installed such cameras in New York City, said once motorists get used to them, rear-end collisions ``normalize.''
Signs will be required to alert motorists to the cameras, and Anderson, of AAA Mid-Atlantic, said clear signs ``would definitely cut down on rear-end collisions.''