Speed Cameras Shown to Increase Road Efficiency

by B' Spokes
Wednesday, October 22 2008 @ 11:54 AM GMT

WASHINGTON, D.C. (September 18, 2008) — Although drivers tend to slow down when driving through a photo enforcement zone, a recent study shows that speed cameras actually reduce travel time and improve travel time reliability. The landmark study is the first in the U.S. to analyze multiple effects on driver behavior, travel time, societal costs, and road safety.

The study, which became available to the public this summer, looked at a trial photo enforcement program on a segment of Arizona State Loop 101 in Scottsdale. The program — the first in the U.S. to use fixed-site speed cameras on a freeway — ran from January through October 2006 and cited drivers going at least 11 miles over the 65 mph speed limit.

Simon Washington, the Arizona State University engineering professor who co-authored the report, found that the speed camera program “not only improved safety but also improved mobility through travel time savings, improved travel time reliability, and reduced travel time uncertainty.”

The report found that during the nine month speed camera trial program

mean traffic speeds were reduced by nine mph
total crashes were reduced by 44% to 54%
injury crashes decreased by 28% to 48%

The annual estimated safety benefits ranged from $16.5 to $17.1 million, based on medical costs, quality of life costs and other costs (lost productivity, wages, long-term care, etc.).

The report estimated that the reduction in crash frequency saved approximately 1,336 vehicle-hours a year when crashes blocked one lane and 45,060 vehicle-hours a year when crashes blocked two lanes. The annual benefit of travel time savings ranged from a low of $20,040 (one-lane blockage crash assuming $15/hr value of travel time savings) to a high of $901,200 (two-lane blockage crash assuming $20/hr of travel time savings). The six speed cameras (three facing in each direction of traffic) produced a clear change in driving behavior.

The average number of daily speeding detections per camera was

162.2 during the warning period;
129.7 during the program period;
1,482.4 during the after period; and
134.68 during the reactivation period.

“This study confirms what we have believed all along,” said Barbara Harsha, Executive Director of the Governors Highway Safety Association (GHSA). “By reducing crashes, photo enforcement not only saves lives but also enhances traffic flow and shortens time in the car.”

“Evaluation of the City of Scottsdale Loop 101 Photo Enforcement Demonstration Program” can be found at http://www.azdot.gov/TPD/ATRC/publications/project_reports/PDF/AZ684.pdf. In addition to Washington, other co-authors are Kangwon Shin and Ida van Schalkwyk from Arizona State University. The report was prepared for the Arizona Department of Transportation in cooperation with the U.S. Department of Transportation and the Federal Highway Administration.