Comparison of accident rates for two truck configurations

Industry-supplied data allowed a structured statistical comparison of the safety performance of tractor-semitrailers (singles) and doubles by comparing their accident experience on the same routes for 3 years. This paired structure essentially controls for roadway, environment and traffic conditions. Separate comparisons of vehicle safety performance were conducted for access- and non-access-controlled highways, local streets, and parking lots. The generalization derived from the study is that doubles are generally as safe or safer than singles, even when specifically controlling for roadway, traffic, and environmental conditions. This study was conducted on routes that are approved for doubles' operation. It is, therefore, not appropriate to extrapolate these findings to any specific route.