By on August 12, 2009

The state of Arizona began deploying speed cameras on freeways last year for the stated purpose of slowing drivers. Scottsdale was the first jurisdiction in the state to use such cameras and issued $17 million worth of automated freeway tickets before the state took over the program. The city paid a local professor $75,000 to create a study to show that drivers had slowed. An expert in radar technology produced a report last month insisting that is not the case.

Craig Peterson is the founder of, a company that has performed independent evaluations of various types of radar and laser speed detection equipment for nearly two decades. Peterson performed an independent and simple test of Arizona’s photo radar program to verify whether drivers have actually slowed.

“Accurate statistics of accidents at camera locations won’t be available for some time yet, but now that scores of speed cameras and a fleet of 100 photo radar vans have been deployed, it certainly isn’t difficult to measure the cameras’ effect on freeway speeds,” Peterson explained.

Peterson set up his equipment on freeways in Glendale, Mesa, Prescott Valley and Star Valley. He used a Kustom Signals Pro Laser III lidar gun and LaserStat traffic survey software to measure speeds one-half mile before a speed camera and one-half mile after the camera during free-flow traffic. The sample included at least 200 measurements at each location using the speeds of cars in each travel lane. In all cases, Peterson strictly adhered to accepted engineering practices for performing a traffic speed study.

“Interestingly, the numbers from every site were nearly identical,” Peterson wrote. “Far from slowing traffic, the cameras had no effect on freeway 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.”

The speed limit on the Loop 101 freeway is 65 MPH, although engineering guidelines suggest that limits be set at the 85th percentile speeds, the rate at which the vast majority of motorists safely travel. Peterson’s measurements found that the 85th percentile speed on the Loop 101 ranged from 70 MPH to 73.4 MPH at the original photo radar locations in Scottsdale. Before and after speeds were identical except by a statistically insignificant increase in the after speed at two locations.

The National Motorists Association, which opposes the use of speed cameras, was not surprised by the findings.

“Believing the claims of companies that sell photo enforcement equipment or municipalities that use this equipment is like believing any commercial produced by a company that is trying to sell you something,” the group explained on its website. “There is no independent verification that photo enforcement devices improve highway safety, reduce overall accidents, or improve traffic flow.”

Source: Are Speed Cameras Effective? (, 7/8/2009)

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7 Comments on “Arizona: Independent Test Shows Speed Cameras Do Not Slow Drivers...”

  • avatar

    We read: “Test shows speed cameras do not slow drivers.”

    They read: “Test shows unlimited revenue collection possibilities without the need to move cameras to new locations!”

  • avatar

    This is known. A study in the 80’s in NY State found that marked Trooper patrols had a small impact on speeds within sight and none at all just before or after.

    People follow an 85th percentile rule.

    There was radar…and the detector.
    There was laser…and the jammer.
    Now, cameras…and the GPS alert.

    A camera set up combined with under posted speed limits will always catch the unwary part of the 70% speeding. They know that, and we do too.

    So do we the people, which is why camera merchants, for all their “successes”, find the US not welcoming.

    New Yorkers should be interested that Gov. Patterson proposes speed cams in his Governor’s Budget proposal. “to raise revenue”.

  • avatar

    Well, speed cameras do not slow cars. That’s a fact. But not a truth.

    Is it possible that it’s not as effective as intended?

    Or, it’s so effective that when the worst 1% of drivers are deterred, overall flow speed actually went up?

    We don’t have enough info to reach a conclusion.

  • avatar

    Driving through Phoenix on I-10 a month or so ago I sure felt like traffic was travelling much slower than what I’d witnessed in the past.

    Cameras don’t kick on until 11 mph over the limit and traffic was moving much slower, I’d say close to being right at the limit.

    This was not rush hour and I felt there was plenty of opportunity for speedier travel.

    I’d say it’s changed from when I went through before when I felt like I was going to be run down.

  • avatar


    Unfortunately, the economic slowdown has also slowed down traffic here in Virginia where there are no speed cameras. The (math-impaired) left lane Prius drivers think they’ll save big money by driving 5mph slower, I guess.

    There are always multiple factors involved, but one thing is certain: the revenuers will use whatever bogus argument they can to prop up a moneymaking scheme.

    That, and “slower” has absolutely nothing to do with “safer.”

  • avatar

    Of course speed control and slowing traffic down are most likely not the motive behind the cameras. Revenue is.

  • avatar

    Chicagoland does not use fixed cameras, but some idiot vans. I got hit with a $400 ticket for going 67 in construction zone of 45mph. The day after I got the ticket I drove 50 through the zone. I can’t count the number of people who gave me the finger or got in front of me to test emergency braking or wash their windshields. My experiment lasted for one day.

    Oh and the ticket came 6 weeks after the date of the violation, so who knows how many I could have out there.

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