交通摄像头有多大作用?

You—well, not YOU—race through an intersection as the light turns red. And then you notice the camera. They got you. And a ticket is on its way. Well, researchers have quantified the financial benefit of the cameras in one city. Turns out it’s from more than the speeding tickets.

In Barcelona, more than 12,000 people were being injured every year in traffic accidents. Making drivers slow down has proven to be the best way to reduce accidents—and these cameras succeed in getting drivers to lower their speed.

The researchers examined data from eight cameras installed on Barcelona’s beltways over two years. They compared the before and after accident rates for those highways, and compared those with highways that had no cameras.

Because of the cameras, there were 364 fewer accidents in the two years, and 507 fewer injuries. [Joan Mendivil et al, in Injury Prevention, Speed cameras in an urban setting: a cost-benefit analysis]

Even with the cost of the cameras and monitoring them, the city saved the equivalent of at least some $9 million—possibly much more. The biggest benefits were from vehicle damage that didn’t happen and medical bills that were never incurred. Not to mention gas money saved from not gunning the engine.

—Cynthia Graber