The Red-Light Camera Miracle

Editor’s Note: Late last year,
The Chicago Tribune performed an independent safety analysis of the city’s extensive red-light camera network. The study concluded that “the cameras do not reduce injury-related crashes overall—undercutting Mayor Rahm Emanuel’s primary defense of a program beset by mismanagement, malfunction and a $2 million bribery scandal.” The study also found that the city’s claims of a 47 percent decrease in side-impact collisions was grossly overstated and that rear-end collisions actually increased. This news prompted NMA ally Jay Beeber, executive director of Safer Streets L.A., to provide the following analysis on why red-light cameras have no positive impact on intersection safety.


The biggest problem with the theory that red-light cameras prevent side-impact collisions is one that is rarely ever addressed—what’s the mechanism by which this allegedly occurs?

Let’s look at the pro-RLC argument. Camera supporters claim that by putting up ticketing cameras, drivers will “adjust their behavior” or “drive more carefully” around the cameras, making the intersections safer. They never go beyond that explanation.

So let’s try to answer the question of how red-light cameras perform their magic. What behavior is being changed or in what way are motorists driving more carefully?

Red-light cameras only target one type of behavior—when a driver could have stopped with a safe and comfortable deceleration rate but instead chooses to “gun it” to try to make it through so they don’t have to stop for the light. I think it’s silly to pretend that this doesn’t happen. It unquestionably does. But not to the extent that many think and usually only when a driver is within the indecision zone. It’s very unlikely that a driver further than about 5-6 seconds travel time to the intersection will try to make it. So the driver who exhibits the behavior targeted by the red-light cameras will, if they fail, run the light by a fraction of a second.

What’s the effect of this? First, let’s consider a driver who does not run the light but crosses the limit line a fraction of a second before the light turns red. In states with a permissive yellow law (meaning that if your vehicle breaks the plane of the intersection before the light turns red, you have not committed a violation, even if the light turns red while you’re still in the intersection) this is perfectly legal. If there’s no all-red clearance interval, cross traffic could start up before this driver makes it across the intersection. Even then, due to start-up delay, there’s unlikely to be a collision, but it could happen, especially if a driver approaching from the cross street sees the light changing ahead and enters the intersection at speed.

Now consider the red-light runner who crosses the limit line a fraction of a second after the light turns red because he decided to go when he could have stopped. What is the practical difference between this driver and the one above? Nothing. That fraction of a second probably has no more likelihood of causing a collision. There is very little, if any, difference in crash exposure due to these two types of drivers.

Of course, with a sufficient all-red clearance interval both of these types of collisions will be avoided.

So let’s say that red-light cameras are 100 percent effective in changing the behavior of the driver who decides to push the yellow (which they are not). What have we accomplished by changing this behavior? Nothing. It’s just not possible to eliminate side impact collisions by scaring drivers into not pushing the yellow because they aren’t the cause of these collisions in the first place.

Now there’s a special case where this could make a difference. With a permissive left turn signal, drivers turning left might think an oncoming driver is going to stop, so they make the turn in front of the oncoming vehicle. The vehicle doesn’t stop and a collision occurs. Of course this can also happen in the scenario where the driver doesn’t run the light and crosses the limit line just before the light turns red. It’s likely that many collisions which are tagged as red-light running collisions are actually ones in which the left-turning driver jumped the gun and then claims the oncoming driver ran the red.

The way to avoid the left turn opposed collision is to have a protected left turn lane and signal. This prevents this type of collision 100 percent of the time.

As for crashes caused by late-into-red red entries, they are due to the driver not recognizing the light is red. Red-light cameras can’t prevent this from happening either so they can’t be effective in reducing or eliminating them.

I’m also not dealing with the length of the yellow light here because I’ll assume for the sake of argument that it is long enough for the vast majority of drivers in the vast majority of situations to either stop or go appropriately.

So I go back to the original question that red-light camera proponents and “researchers” who claim the data show even a modest reduction in red-light running collisions due to red-light cameras are never asked to answer. What’s the mechanism by which red-light cameras have supposedly reduced these collisions?

Their answer is usually the same as the punchline to this famous Sidney Harris cartoon: “Then a miracle occurs.”

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7 Responses to “The Red-Light Camera Miracle”

  1. Soby says:

    What states require you to clear the intersection before the light turns red?

  2. Ken in NH says:

    Another question regarding the RLCs change behavior theory is this: If the threat of a fatality accident and/or expensive repairs and increased insurance rates do not discourage the red light runner, why would a $75 civil fine?

  3. Dave Webb says:

    The problem with cameras is it is a scam put forth by crooks for crooks in government.
    In the contract between government and company is a clause that says it all.
    That clause says in English that the yellow light must be set at 3.5 seconds.
    What is wrong with that?
    At 35 miles per hour it takes 3.5 car lengths to stop according to the Ohio State Highway Patrol. The rule of thumb being that it takes one car length for every ten miles per hour you are going.
    I do not know anyone that doesn't go a little bit faster than that on a major highway in a city designated at 35. More than likely they will be going 40 or 45 miles per hour unless it is stopped by local police. So you are really talking an average of 4 car lengths to stop at a light.
    People behind you are often not aware which makes it dangerous to stop suddenly at a light risking a rear collision.
    So if you are within 20 feet when the light changes you have no option but to run the light.
    I'll go further. If you are within 3 car lengths of the light you cannot stop in time. Yet the quick yellow light makes you in violation of the law.
    If you are on a rural route with 45 miles per hour it is even worse.
    The traffic light camera companies are fully aware of the engineering and have put this 3.5 second yellow right in the contracts.
    That means they are deliberately engineering people running red lights.

  4. Fred762 says:

    Looks like a simple solution could be 1. all-red for a second or two and 2. dedicated L turn lanes..but thsese don't bring in $$$ do they?

  5. Keenan says:

    Yes it is another revenue maker in there minds. Best way to make intersections safer is to have a 2 second delay after the light turns red and the other turns green.

  6. josh says:

    actually in Washington state they were caught shortening the yellow light time, they do this as well causing even more rear end collisions…inevitably deaths so they actually have blood on their hands. The banks are in cahoots with the local municipalities in a revenue sharing agreement. it's actually much worse than you portray in your article sir.

  7. Charles says:

    On a road traffic or news web page online. It said that Chicago,IL is about 66% covered in Red Light and Speed Cameras around the city. Chicago, Illinois has turned into the Red Light and Speed Camera capital of Illinois. Scameras of Illinois. The Cameras are also state wide. They are used for renevue to make more money. People are not made of money people!