Red light cameras

Running a red light is a very dangerous thing to do. Red light cameras that photograph cars that do this are proliferating in many areas. They take a photo of offenders who are then cited and fined. But one study done in Houston finds that while they do reduce the number of people running red lights, they do not necessarily reduce the number of accidents.

During the past decade, over 438 U.S. municipalities, including 36 of the 50 most populous cities, have employed electronic monitoring programs in order to reduce the number of accidents. Red light camera programs specifically target drivers that run red lights.

Evidence clearly shows that camera programs are effective at decreasing the number of vehicles running red lights. In one study in Virginia, red light cameras reduced the number of total drivers running red lights by 67 percent.

However, cameras can have contradictory effects on traffic safety. Some drivers who would have otherwise continued to proceed through the intersection when the light is yellow or red will now attempt to stop. That means that the number of accidents caused by vehicles not stopping at a red light will likely decrease.

But the number of accidents from stopping at a red light – such as rear-end accidents – is likely to increase. That’s not an inconsequential side effect. Some drivers will attempt to stop, accepting a higher risk of a non-angle accident like getting rear-ended, in order to avoid the expected fine.

When the Houston cameras were removed, angle accidents increased by 26 percent. However, all other types of accidents decreased by 18 percent. Approximately one-third of all Houston intersection accidents are angle accidents. This suggests that the program’s drawbacks canceled out its benefits.

What this study shows is that far too many people tailgate, i.e., drive too close to the car in front based on the speed. When I slow down to stop because of a yellow light, I usually look in the mirror to see if the car behind may hit me and sometimes I edge forward a bit to give them more time to stop. If tailgating were reduced, then red light cameras would result in reduced accidents. Also, rear-end collisions are less likely to cause serious injury than getting broadsided.

One of the things that I would like to see more of are those signs by the roadside that tell you how fast you are traveling. Whenever I see them, I instinctively check my speed to make sure that I am not going too fast. Placing one of those signs right next to speed limit signs may help reduce speeding, another cause of accidents. Since these speed detector signs seem to be solar-powered, the maintenance costs should be low.


  1. Michael Sternberg says

    The cost of speed indicators may be too prohibitive for municipalities to widely deploy them.

    I heard that it can cost several thousand dollars to run a single sign for just a week and obtain statistics for the velocities observed over time (which, BTW, are good enough to track slowdowns upon approach). Besides a profit motive, manufacturers might justify such high “licensing” costs with legal liability, which can get expensive. For example, the statistics can be used to set or alter local speed limits based on the observed speed for certain vehicle percentiles.

  2. Mano Singham says


    If we can take the data collection out and leave just the speed display, I wonder if the cost would reduce by much. The device would then be stand alone and would not need to be linked to any central station.

  3. says

    Our district council has a transportable speed indicator that gets moved around week by week, reminding locals of their lack of attention. It certainly makes the brake lights of vehicles ahead of me to come on suddenly.

    As for red light cameras, most people get fined for shaving the gap between their red light and the cross traffic getting the green. These don’t cause the accidents and they are more likely to stop in a hurry to avoid fines. The ones that can’t see a red light end up having a collision anyway.

    Mild risk taking is what keeps some people awake.

  4. jazzlet says

    My local metropolitan council has a moveable speed indicator which spends some of its time near my house which is on an A road (ie for the non British, a road considered to be the next level down from a motorway (freeway) and part of the National Highway Network, ie roads that distance traffic is expected to, and signed to use). Even though it is also a residential street with a speed limit of 30mph neighbours have seen the indicator display 68mph, and that is very shortly before a 90 degree bed in the road. I don’t know how fast the guy that manage to flip his car on the straight stretch was going, that was on a dry day in daylight, but he was goig in the opposite direction so his speed wasn’t caught. One of the reasons they are moved around is because people get used to them and they are more effective when novel, but that only affects the motorists that are bothered, so I’d actually like to see it linked to a speed camera. If it was it might even cut the speeds enough so I could get out of my driveway safely.

  5. jazzlet says

    Oh as far as the red light problem goes, apart from tailgating another problem is a lot of drivers don’t know when they should stop, ie that the yellow is a warning which gives you time to judge whether you can safely stop in front of the line, and be long enough that any driver paying attention should be able to make that decision before it turns to red. By the time the light turns to red you should be passed it on the junction or stopped behind the line. Far too many drivers just see yellow as an incentive to get passed the light and don’t consider stopping until the light is already red.

  6. jazzlet says

    Urgh, sorry that should be ‘safely stop behind the line’ in both cases. I did preview too.

  7. says

    An additional factor to consider is the amount of time the yellow light is “on”. This varies from intersection to intersection and can be programmed by traffic control authorities. I have no particular expertise in this area, however, I am just recalling some articles I read in Car and Driver magazine a few years back. Their upshot was that some communities shorten the yellow “on” period, giving police more opportunities to ticket drivers for red light infractions.

  8. Mano Singham says

    gregpeters @#8,

    Yes, that kind of abuse did happen. But I seem to recall that increased public vigilance (and of course lawsuits) rolled back some of those efforts.

    The efforts by municipalities to shift the emphasis from safety to revenue generation is a real menace.

  9. Joe says

    It was reported multiple times that crashes went UP in Philly at red-light camera intersections. How was this missed? How can the officials deny this, when it was in black and white? How much traffic also diverts to other streets to avoid the cameras? How are crashes counted in the data used to justify cameras?

    There may be poor traffic engineering and predatory enforcement where cameras are used. It seems that cams may be setup to ticket safe drivers. Who cares if they have to pay or crashes go up? Who cares if the wrong guy is even cited? Who cares if the ticket has an erroneous reading?

    Yellows may be too short(really bad for turning), people can be cited a split-second after the lights change, for stopping over the stop line, or a non-complete stop for a right-on-red turn. Who can defend this setup?

    All you need are speed limits set to the 85th percentile free-flowing traffic speed, longer yellows, decent length all-red intervals, and sensors to keep an all-red if someone enters late. No crashes! Can also sync lights and use sensors to change them and know where cars are. After simple changes are made, only egregious violators should ever be cited.

    Check out the National Motorists Association for unbiased driving info.

  10. EigenSprocketUK says

    Wow, if it’s true that red-light cameras increase the number of rear-end collisions… just how fast and close do people drive in the US, and how hard are people braking? This seems to be exposing the real risk factor.

  11. Mano Singham says

    I am afraid that tailgating is a real issue. People do drive too fast and too close to the car in front. That is why we see multiple car pileups on occasion.

    When I was learning to drive, a friend who was teaching me convinced me to take pride in the smoothness of speed changes, to drive so that one did not brake hard nor accelerate too rapidly. That lesson has stayed with me.

  12. says

    Studies done by unbiased groups, those without financial or political influence conflicts of interest, almost always show no net safety effects from red light cameras and sometimes show significantly increased total crash rates. “Studies” published by groups with conflicts of interest frequently but falsely claim safety benefits from the cameras. Violation rates are almost entirely dependent upon yellow intervals that are set properly-long for very low violations or deliberately and less-safely set too short for the actual conditions for the express purpose of increasing violations, tickets and revenue. The latter is a vicious for-profit racket that no one should tolerate for any reason -- and is the case for any red light camera program with significant profits above the high costs of the cameras.

    Because most red light cameras are for-profit rackets, red light cameras should be illegal in every state as they are in some already. Involving for-profit camera companies in any part of traffic enforcement essentially guarantees a corrupt emphasis on profits, sometimes at the expense of less safety. NO ONE should tolerate these rackets.

    James C. Walker, National Motorists Association

  13. says

    Privatization of government functions is the problem. Or using law enforcement as a funding source. It’s not just red light cameras. It’s private prisons. It’s tacking on fees to court fines. It’s using private companies to collect fines.

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