The Truth About Speed Cameras: They Don’t Work

Anyone who believes that speed cameras have a large impact on the speed of the vehicles on a freeway should check out this study published last month.

In order to evaluate how effective speed cameras are at reducing driver speeds, Craig Peterson of conducted an experiment using the speed cameras in Arizona.

Here’s an excerpt from his findings (emphasis added):

Over a period of weeks this spring I conducted traffic surveys near speed vans and fixed cameras in several locations around the metropolitan Phoenix area. I did the same in Mesa, Glendale, Prescott Valley and Star Valley, Arizona.

To create before/after speeds, I first measured speeds one half mile before the camera, then at the same distance after the camera. If the speed camera tub-thumpers are right, the after speeds should be noticeably slower.

I conducted the surveys using accepted Institute of Transportation Engineers (ITE) methodologies […] I sampled cars equally from each travel lane and to make the statistics even more unimpeachable, I recorded the speeds of at least 200 vehicles at each location, twice the number dictated by ITE guidelines. […]

Interestingly, the numbers from every site were nearly identical.

In [the] composite chart of representative results [included below] from four of the freeway locations, it can be seen that far from slowing traffic, the cameras had no effect on freeway speeds.

In fact, at some locations average speeds were higher after the cameras. Okay, the small increases are statistically insignificant.

But the numbers are clear: speed cameras do not decrease highway speeds.

Aside from a brief dab at the brakes by a few drivers in reaction to fixed speed cameras—frequently resulting in screeching tires from cars behind—most seemed oblivious to them. Hardly any slowed in reaction to the speed vans.


As Mr. Peterson points out at the end of the article, if speed cameras have no impact on driver speed, then what are they good for?


Oh, right.

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