Impact of an automatic speed enforcement program on Loop 101 Freeway in Arizona.
Scottsdale, Arizona, United States
Evaluation of the City of Scottsdale Loop 101 Photo Enforcement Demonstration Program: Final Report AZ-684
Summary Information
In Scottsdale, Arizona, a nine month speed enforcement camera demonstration program (SEP) began in 2006 on a 7.8 mile segment of the SR 101 freeway. While fixed site photo enforcement programs are not uncommon on arterials, this program may have been the first to be deployed on a freeway. This study was conducted to estimate the impact of the SEP on traffic safety, speed, speeding behavior, and daily travel time uncertainty. More specifically, the objectives were to estimate: the impact of the SEP on speeding behavior; the changes in mean speed due to the SEP; the impact of the SEP on traffic safety in the enforcement zone; the total travel time impacts; and the economic impacts of the safety effects. An evaluation estimated the safety and mobility effects of the speed-enforcement program by conducting statistical analyses of crash and crash cost data, traffic data (volumes, travel times, average speeds, and speeding behavior), and economic factors.
This study was conducted to estimate the impact of the SEP on traffic safety, speed, speeding behavior, and daily travel time uncertainty. More specifically, the objectives were to estimate: the impact of the SEP on speeding behavior; the changes in mean speed due to the SEP; the impact of the SEP on traffic safety in the enforcement zone; the total travel time impacts; and the economic impacts of the safety effects.
Five time periods are referenced in the analysis.
- Before (2001 – 2005: various period)
- Warning (01/22/06 – 02/21/06)
- Program (02/22/06 – 10/23/06)
- After (10/24/06 – 12/03/06)
- Reactivation (02/22/07 – 06/29/07)
FINDINGS
The crash data analysis indicated that the speed-enforcement program was effective in improving overall crash risk in the enforcement zone, although the effect on rear-end crashes is uncertain.
- The analysis indicated that the program decreased the total number of target crashes by 44 to 54 percent,
- The total number of injury crashes decreased by 28 to 48 percent.
- The Property Damage Only crashes decreased by 46 to 56 percent. (The range is attributable to the different analytical methods used in the evaluation.)