Determining the influence of Speed Cameras in Reducing Speed Violations using Bayesian and Comparison Group Methods(A Case Study in Ghazvin-Rasht and Bam-Kerman Roads)

Speed of the motor vehicles is one of the main risk factors in traffic safety, as it can increase both the chance and the severity of a crash.  In order to achieve an improved traffic safety  by  influencing  the  speed  of  travel,  road  authorities  may decide  to  lower  the  legally  imposed  speed  limits. In this study, information from speed cameras and traffic counters installed in Ghazvin-Rasht and Bam-Kerman interstate highway were used to explore the effectiveness of speed cameras in reducing the number of speed violations. Various methods of Before-after stufy, such as Empirical Bayes, and Comparison Group methods were employed to analyze the obtained information from the speed cameras installed in the studied highway. Results obtained from the Empirical Bayes method demonstrated 90 and 94% reduction in the number of speed violations at two of the studied locations. Comparison Group method also suggested 80-95% decrease in the number of speed violations at the two study locations. Overall, speed cameras proved to be effective tools in reducing the number of speed violations in these case studies.