Estimates of accident and release rates are essential for conducting risk assessments in routing studies for highway transportation of hazardous materials. Recently published literature has emphasised both the importance of these rates in risk assessment and the significant shortcomings of the available data. New truck accident rates are developed as a function of roadway type and area type (urban or rural) from state data on highway geometrics, traffic volume, and accidents. Release probabilities in accidents have been derived from a combination of federal and state truck accident data bases. A revised model for the accident probability portion of the U.S. Department of Transportation hazardous materials routing guidelines is recommended, and its application is illustrated using accident and release rates derived to substitute for existing default values. Statistical tests based on the chi-squared and poison distributions are provided to determine whether accident rates based on site-specific data or systemwide values, such as those derived here, should be used for any particular route segment.
Samenvatting