A national risk assessment for selected hazardous materials transportation.

This report details a quantitative risk assessment conducted for transportation of selected hazardous materials on a national basis. These materials include six toxic-by-inhalation (TIH) chemicals, which account for more than 90% of the total TIH transportation-related risk; liquefied petroleum gas; gasoline; and explosives. For TIH materials, both highway and rail transportation are considered, and two classes of incidents are examined--those that occur (1) during a traffic accident or a train derailment and (2) while en route from the origin to the destination, but not during an accident or derailment. For the other materials evaluated in the study, only accident-related incidents for highway transportation are considered because transportation-related risk for these materials is dominated by highway incidents. The report describes the hazardous materials and consequence levels evaluated; the risk assessment methodology; the databases used to determine hazardous materials commodity flow and incident rates; and results of the study, including quantitative risk distributions and risk measures for the materials evaluated. The results suggest that, compared with other types of transportation risks encountered by the public, overall societal risks due to hazardous materials transportation remain relatively low. However, the potential exists for very serious accidents involving large numbers of injuries and fatalities, especially for TIH materials, although the probability of such events is low. This study also reveals areas of substantially higher risk relative to hazardous materials transportation risk as a whole.