Evaluation of California's commercial driver license program.

This study evaluated the traffic-safety impact of the California Department of Motor Vehicles' Commercial Driver License (CDL) program. The program, initiated on 1 January 1989, began a new commercial-license classification and endorsement system, implemented stronger licensing standards and more comprehensive tests of knowledge and driving competency, required drivers to report specific violations to employers, and provided for more stringent post-licensing sanctions on negligent operators. The effect of the program on fatal and fatal/injury accidents involving heavy vehicles operated by drivers licensed in California was assessed using intervention time-series analysis. The results indicate that the CDL program did not have a statistically significant effect on either accident measure.