Wednesday, October 22 2008 @ 11:54 AM UTC
Contributed by: B' Spokes
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.”