Evaluation of the Scottsdale Loop 101 automated speed enforcement demonstration program

Area of Science:

• Traffic safety research
• Transportation engineering
• Public policy analysis

Background:

• Speeding is a primary cause of traffic accidents.
• The city of Scottsdale, Arizona, pioneered the first fixed-camera speed enforcement program (SEP) on a US freeway.

Purpose of the Study:

• To analyze the impact of a pioneering freeway speed enforcement program on speeding behavior, crash occurrences, and economic consequences.
• Evaluate the effectiveness of fixed-camera speed enforcement on a limited-access urban freeway.

Main Methods:

• Generalized least square estimation to assess changes in speeding behavior.
• Before-and-after analysis (with comparison group and traffic flow correction) and empirical Bayes analysis to evaluate crash impacts.
• Economic analysis using Arizona-specific crash-related injury costs.

Main Results:

• Average speeds decreased by approximately 9 mph within the enforcement zone.
• Speeding detection frequencies (speeds ≥ 76 mph) surged 10.5-fold after the program's termination.
• All crash types decreased, excluding rear-end collisions, with estimated significant annual safety benefits of $17 million.

Conclusions:

• Fixed-camera speed enforcement effectively reduces freeway speeds and crash rates.
• The program demonstrated substantial economic benefits through reduced crash-related injuries.
• The findings support the implementation of similar speed enforcement strategies in urban freeway environments.