PROCEDURE FOR DEVELOPING TRUCK ACCIDENT AND RELEASE RATES FOR HAZMAT ROUTING

To conduct risk assessments in routing studies for the highway transportation of hazardous materials (hazmat), estimates of accident and release rates are essential. Published literature underscores the importance of these rates in risk assessment, and the significant shortcomings of the available data. Truck accident rates are developed in this paper as a function of roadway type and area type (urban/rural) from state data on highway geometrics, traffic volume, and accidents. Release probabilities in accidents are derived from a combination of federal and state truck accident data bases. The procedure is presented in detail. A discussion of the dangers of combining data from different states is also presented, along with justification for the decision of the writers to do so. A revised model for the accident probability portion of the U.S. Department of Transportation (DOT) hazardous materials routing guidelines is recommended. Statistical tests are presented to determine whether accident rates based on site-specific data or systemwide values, such as those derived in this paper, should be used for any particular route segment.