The Relationship Between Private and Commercial Vehicle Driver Records and Accidents in Michigan

The primary objective of this study was to determine whether previous accidents and citations are reliable predictors of future tractor-trailer heavy truck accidents in Michigan. In addition, the background material on accident trends shows how heavy truck safety policy was formed at the Michigan Department of Transportation.\nHistorically, accident prediction models have been able to explain only small portions of the accident experience. More recent studies have tended to show that previous citation and accident experience were good predictors of commercial vehicle accidents. Most studies have suffered from an admitted lack of exposure data and incomplete accident statistics.\nThrough the use of induced exposure techniques or the "innocent victim" concept, a research design was constructed to minimize the influence of unknown exposure and data voids. A large accident data base was assembled with all reported accidents in Michigan for the years 1982 to 1987. This database included driver histories from the Michigan Department of State and drew upon the computing and analysis power of the Michigan Department of Transportation's Unisys A-15 computer and the Michigan Dimensional Analysis Surveillance (MIDAS) system.\nThe researcher concluded that previous accident experience is not a reliable predictor of future tractor-trailer accidents. There appears to be little or no relationship between the type of vehicle involved in an accident, whether it is private or commercial, and subsequent commercial accident experience. Previous citations and driver age appear to be possible predictors of future heavy truck accidents. No single large group of drivers emerged as a target for intensive training or enforcement efforts. These conclusions, however, depend on validation of the induced exposure concept used.\nRecommendations for future research include a driver survey to validate the innocent victim concept and a methodology to evaluate the Commercial Motor Vehicle Act of 1986.