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IIHS: Red-Light Cameras Improve Safety, Reduce Violations

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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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Comments (8)
  1. I just read IIHS report. As usual such reports ignore the the scientific method. The first step in the scientific method is to identify the problem. The problem is "Why do people run red lights?". IIHS never gets to the first step. Instead IIHS assumes that all drivers have suicide complexes and are to blame even though traffic engineers by design introduce systematic errors called dilemma zones into every signalized intersection--which literally force drivers to run reds by up to 4.5 sec.


    The purpose of the red light camera is to first punish and profit from drivers running red lights. The marketting ruse is safety.

    I have the red light camera data from Cary, NC. It shows that the NCDOT is responsible for 99.7% of all RLR.
     
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  2. The IHS report is chock full of holes. I've lived in many States, and whereever these cameras were in operation, there were MORE accidents...namely, rear end crashes. To say these cameras are not put up for profit, are false, in my opinion.
     
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  3. I think we all agree that profit is, in part, the motivation for red-light cameras. However, this report and others have documented the fact that red-light cameras can reduce the number of red-light infractions, which often lead to accidents.
     
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  4. Richard, see first hand that IIHS is lying to you. The graphs in the following URL show the raw red light running citations per month per approach in Cary, NC for the last 8 years. The data comes directly from Redflex. I have shown on the graphs the points in time where the NCDOT has changed the yellow light
    durations. Also note the disparty of the y-axis between intersections. The greatest $ come from turning lanes because the underyling formula engineers set yellows by opposes the laws of physics for turning drivers. Note that a 0.5 second increase in yellow decreased RLR by 80%. Note that a 1.0 sec yellow decrease increased RLR 1000%.

    http://redlightrobber.com/red/links_pdf/north-carolina/Cary-Citations-By-Intersection.pdf
     
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  5. I don't think you're comparing apples and apples. The IIHS study examines the effect of red-light cameras on the number of red-light violations. Specifically, it's concerned with the way in which drivers self-police to reduce infractions.

    Your study, on the other hand, centers on ticket frequency and yellow-light lengths, which seem to have been manipulated by the town of Cary in ways that don't meet state specifications. It measures infractions, but only insofar as they're the result of yellow-light tampering.

    I agree that your data seems to incriminate the Cary police department, but that doesn't invalidate the findings of the IIHS study at all. Unless I'm missing something, the studies have little/nothing to do with one another.
     
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  6. The IIHS findings are irrelevant because their investigation does not use the scientific method. Presuming drivers are to blame for bad intersection design invalidates IIHS's conclusions and IIHS advocating the punishment of drivers is unethical.

    All cities adjust yellow and all-red times, gaps and green extensions. Intersections are always in flux. IIHS does not report any of it. My main point is that cities do not have to go out of the way to push certain classes of drivers to run red lights. All cities have to do to accomplish that is to simply apply the federal standards. The standards are the problem.

    Remember the Corollas with the sticky brakes? Do you think taking a picture of the driver helps the driver?
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  7. Do you know what drives IIHS to write pro camera reports? IIHS is a consortium of insurance companies that profit off of insurance points. In Florida IIHS donates to the policemen's retirement fund every time the police flash a driver with a red light camera.

    The senior traffic engineer for IIHS was Richard Retting, the same person who is the father of the red light camera in America.
     
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  8. They can document all they want. I've seen it first hand at the locations of these red light cameras. There are MORE accidents with rear end collisions. That'a all the documentation I need.
     
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