IIHS: Red-Light Cameras Improve Safety, Reduce Violations

January 25, 2013

Traffic cameras cause a lot of controversy. Some folks appreciate the way that the mere presence of a camera can make motorists drive more cautiously. Others see them as a scam foisted on the public by for-profit companies, working in cahoots with local police departments. 

But the Insurance Institute for Highway Safety (IIHS) has just conducted a new study, which reveals that one type of traffic cam -- the red-light camera -- can significantly reduce the number of drivers who run red lights and, theoretically, the many accidents they cause.

Admittedly, the size of the IIHS study was not especially broad: it involved red-light cameras placed at four busy intersections in Arlington, Virgina. The cameras were installed in June 2010 and focused on just one line of approach per intersection. Following the cameras' installation, there was a 30-day warning period. Afterward, drivers were fined $50 per violation. 

In addition to the traffic cams themselves, the IIHS also set up its own video cameras to record red-light runners. It placed two of those cams on the same travel corridors as those being monitored by the traffic cams. It placed two more at non-monitored intersections in Arlington. For control purposes, the IIHS also installed cameras at four intersections in Fairfax County, Virginia, where there are no traffic cams. 

Here are the study's major findings:

  • After one year, infractions at the intersections monitored by red-light cameras declined significantly.  According to the IIHS: "Violations occurring at least 0.5 seconds after the light turned red were 39 percent less likely than would have been expected without cameras. Violations occurring at least 1 second after were 48 percent less likely, and the odds of a violation occurring at least 1.5 seconds into the red phase fell 86 percent."
  • At the two sites located along the same travel corridors as the red-light cams, infractions also declined. Violations taking place 0.5 seconds after the light change dropped 14%; those taking place one second after the light change fell 25%; and the number of drivers who ran lights 1.5 seconds after the change dropped 63%. The IIHS cautions, however, that these are not necessarily statistically significant. The organization also notes that the numbers could've been improved if more funds had been dedicated to advertising the presence of the red-light cameras. As it is, many drivers who didn't pass through the monitored intersections may not have known about them, which likely reduced the spillover effect on other intersections in the region.
  • Curiously, at the sites in Arlington and Fairfax County not being monitored by red-light cams, the number of violations increased. The IIHS suggests that the increase might be due to the improving U.S. economy, which has put more commuters on the roads, but cautions that much more study would be needed to prove that hypothesis.

The IIHS may have the opportunity to test that hypothesis this year: Arlington's 2013 budget contains funds for additional traffic cams. 

Math and statistics enthusiasts can download a PDF of the full IIHS report by clicking here. For more data on red-light stats, visit the IIHS website.

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