D.C. Red-Light Cameras Fail to Curb Accidents

Posted on October 3, 2005  Comments (3)

D.C. Red-Light Cameras Fail to Curb Accidents by Del Quentin Wilber and Derek Willis.

The explanation of the data presented in the article does not support claim made in the headline.

But a Washington Post analysis of crash statistics shows that the number of accidents has gone up at intersections with the cameras. The increase is the same or worse than at traffic signals without the devices.

I’m not sure why accidents should go down at intersections with red light cameras. First what percentage of accidents are caused by red light running? Second, is sending tickets somehow preventive to a specific location?

It would seem the assumption behind their conclusion is people who run red lights are so careful that they notice a camera and chose not to run the red light that they would have otherwise run. That doesn’t make much sense to me. If red light cameras work I would think they work because people learn if they run red lights they will be ticketed and therefore stop running all red lights therefore decreasing red light running at all lights. Or perhaps they don’t and lose their driver’s license due to too many violations.

I can imagine that some people who choose to run red lights figure out that a couple of specific locations that they frequently use have camera and therefore they choose not to run those red lights but continue to run other red lights but this seems unlikely to be of such an impact as to decrease red light running significantly. I would think either red light running everywhere decreases or it does not decrease significantly not that people learn where they can violate the law and where then cannot. Though that is merely conjecture on my part.

Chang and the other traffic specialists said the city should not abandon red-light cameras. Rather, they said, the mixed results indicate that D.C. officials should conduct a thorough review of camera sites.

“They definitely should look at the locations and find where the cameras would be much more effective,” said Nicholas J. Garber, a professor of civil engineering at the University of Virginia who studied the use of red-light cameras in Fairfax County.

I am not sure why they think placing a camera is going to get people to stop running that red light. And I am not sure why that would be what you would target anyway. Wouldn’t you want people to stop running all red lights?

D.C. Police Chief Charles H. Ramsey said he remains convinced that the devices are worthwhile. Even if the number of crashes is not going down, he said, citations for red-light running have dropped by about 60 percent at intersections that have cameras.

Ramsey said the number of accidents would be even higher without the cameras, adding that he would like to install them at every traffic light in the city. He pointed to last year’s steep decrease in traffic fatalities — 45 people died compared with 69 in 2003 — as evidence that the program is working.

Again the article seems to be muddling the analysis of the data. What is the goal of the red lights cameras (to reduce red light running at those intersections or everywhere?). What percentage of accidents are due to red light running?

Injury and fatal crashes climbed 81 percent, from 144 such wrecks to 262. Broadside crashes, also known as right-angle or T-bone collisions, rose 30 percent, from 81 to 106 during that time frame.

Are the conditions (other than the red light cameras) identical to the previous years? If there is more traffic and if more traffic means more accidents then it could be the equivalent of saying that accidents increase as HDTVs were introduced to the marketplace. Why do accidents keep increasing the more that people use HDTV’s. Somehow I think more people are driving with cell phones today than in previous years. Are more accidents being caused by drivers with cell phones?

It may be that the actual data has been analyzed sensibly and the article just doesn’t explain it well, but based on the data from the article the data doesn’t seem to say much of anything of value and doesn’t seem to support the conclusions stated in the article.

The increase is the same or worse than at traffic signals without the devices.

You might think this means the cameras are ineffective. However that would only be the case if drivers were so selective with red light running that they chose to run some red lights and not others. And second if the intersections with cameras experienced the same changes as other intersections (same increases in traffic…) and if those intersections were not at some tipping point which meant they would have actually increased by some percentage in excess of the average intersection absent those cameras.

It could be you have 10 really bad intersections and the traffic exceeds the safe capacity and therefore as traffic increases the level of accidents increases at a much greater rate. Then if you took sensible and effective measures at those intersections but those reductions to the accident level were not enough to overcome the deteriorating other conditions (say increased traffic) they could have worse results compared to the average intersection. That data would not support the conclusion that the measures taken were ineffective however, careless analysis of the data could lead some to believe that is what the data said.

3 Responses to “D.C. Red-Light Cameras Fail to Curb Accidents”

  1. Michael B
    December 31st, 2007 @ 11:35 pm

    Red light camera intersections do increase accidents. Because people do learn where they are located, and then do stop running those lights.

    But why does that increase accidents?

    Because people are so fearful of getting one of those camera tickets, they make and extra point of not running those camera intersections. Or even coming close to running those intersections. Thereby stopping just a little bit sooner than they otherwise would, or than the guy behind them expects.

    Then, to make matters worse, the cities where these are installed learn that they are “cash cows”. So the cities look in increase revenue by shortening the yellow cycle of the intersections. This of course causes some more people to get tickets and lose, and more other people to *avoid* tickets and lose.

  2. S womack
    January 29th, 2011 @ 10:30 pm

    They simply generate revenue, it has little to do with public safety. I’m not a red light runner, I don’t care if there is a camera or not I just don’t do it. Some people are red light runners, they are going to do it whenever they can. Personally I cannot stand people like that, they are the same people who will not merge if a lane ends until the absolute last second causing all kinds of traffic backups just to get a couple cars ahead of you. They put themselves first in every situation they view their lives as more important that other peoples.

  3. Red-light Cameras Save Lives, Could Save More if Used in More Cities » Curious Cat Science and Engineering Blog
    February 1st, 2011 @ 9:53 am

    […] D.C. Red-Light Cameras Fail to Curb Accidents – Do Red Light Cameras Make for Safer Intersections? – Traffic Congestion and a […]

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