Speed cameras help travel time, report says

by Jane Larson - May. 13, 2008 12:11 PM The Arizona Republic

SCOTTSDALE - Photo enforcement cameras on the Loop 101 through Scottsdale slow drivers down a bit, but they save motorists time in the long run because of fewer traffic- snarling crashes, the final report from an Arizona State University traffic expert says.

ASU engineering professor Simon Washington's report calculated that northbound drivers travel the 6.5-mile stretch from Via de Ventura to 56th Street in an average of 10.8 minutes with the speed enforcement program and an average 10.7 minutes without it.

But an accident blocking two lanes of Loop 101 would turn the same trip into one taking nearly 32 minutes, the study found. And since the speed enforcement program cuts the number of accidents approximately in half, drivers gain time overall, the report said.

"It's a daily delay of a small amount, but you more than make up for it with fewer crashes," Washington said.

Having the cameras and reducing accidents saved 1,336 vehicle-hours a year when crashes blocked one lane, and 45,060 vehicle-hours a year when crashes blocked two lanes, the report estimated.

The travel times were calculated for non- peak hours, when traffic is less congested and drivers are more able to speed. Results were similar for southbound trips.

The latest report, released last week, included details of the effect of photo enforcement on travel times.

Scottsdale commissioned the report in 2006. Washington's preliminary report, released early last year, showed that the mean speed of drivers on the camera-controlled stretch through Scottsdale dropped nearly 9 mph, to 64.4 mph during enforcement and 73.1 mph before enforcement.

The posted speed limit in that stretch in 65 mph, and the cameras are set to detect speeding at 76 mph and higher.

The program was highly publicized, and Washington said driver awareness of speeding also may have helped improve safety.

The preliminary report also found tha tthe number of speeders detected by cameras jumped tenfold when the cameras were turned off in October 2006, then fell to near the previous levels when the were reactivated in Febraury 2007.

The final report, released last week, additional speed and crash data and came to essentially the same conclusions.

It estimated that the number of accidents dropped up to 54 percent compared to the number of crashes expected to have occurred without the program. It also estimated that photo enforcement saved Arizonans $16.5 million to $17.1 million a year in medical costs, lost productivity and other costs because of fewer accidents.

Washington also included several recommendations for the program, such as:

• Cameras should be placed at sites with relatively high speeds and a history of severe crashes. That's where the cameras could make the most difference in reducing speed-related crashes.
• Cameras should be placed in plain sight and away from distractions such as ramps and billboards. The increased visibility would lessen the chance that drivers will brake suddenly and cause accidents, Washington said.
• Cameras that measure average speeds over longer sections of freeway may be preferred to ones that measure instantaneous speeds. The alternative method also may reduce sudden braking and accidents, the report said.