Accident rates along congested freeways : final report.

This study quantifies relationships between accident rates and congestion on Californian urban freeways. Accident rates were compared under conditions of queuing and no queuing, and for a variety of geometric and traffic conditions. No matter how the data were stratified, the same picture emerged in the presence of queuing the average accident rate is about two to three times the rate which occurs when there is no queuing.