It’s pretty easy to be cynical about the rapidly growing number of speed cameras in the District, especially when the cameras already brings in more than $80 million a year for the city. But a new study (albeit an internal one with help from an outside firm) suggests that the 87 existing cameras serve a grander purpose: It found they’ve significantly reduced the number of collisions that take place in intersections they’re watching.

The District Department of Transportation found there had been a combined total of 2,240 crashes at the sites of these speed camera for the three years before they were installed. That number dropped to 1,863 crashes for the three years after the cameras were installed. (If the camera hasn’t been around for three years, the study compared the number of crashes that occurred the year before the camera was installed with the number of crashes that took place in the first year of the camera’s existence.)

Before the cameras were installed, there were 841 injuries related to crashes, compared to 673 afterwards. The number of injuries at the locations similarly dropped around 20 percent, from 1,251 prior to installation to 996 after.

The study also found that 13 of the existing camera locations recorded mean vehicle speeds higher than posted speed limits, though none of the means exceeded 15 MPH over the speed limit. At 89 percent of the camera locations, the study found mean speeds were within the speed limit. And 29 camera locations saw speed reductions of at least 10 MPH.

Some high frequency crash intersections where speed cameras already exist: 16th Street NW southbound at Colorado Avenue;, DC 295 at the Benning Road NE exit going northbound; the 100 block of Florida Avenue NW going north and south; and the 4900 block of Connecticut Avenue going southeast.

The study also examined the areas around the 39 planned speed cameras and 169 proposed new speed camera location. So slow down, and read the full study here.

Photo by katmeserin via Flickr/CC BY-SA 2.0