Accident-Cause-Specific Risk Analysis of Rail Transport of Hazardous Materials

Rail plays a key role in the transportation of hazardous materials (hazmat). Improving railroad hazmat transportation safety is a high priority for both industry and government. Many severe railroad hazmat release incidents occur because of train accidents. The Federal Railroad Administration identifies over 300 accident causes, including infrastructure defects, rolling stock failures, human factors, and other causes. Understanding how hazmat transportation risk varies with accident cause is a key step in identifying, developing, evaluating, and prioritizing cost-justified accident prevention strategies, thereby mitigating hazmat transportation risk. The objective of this paper is to develop an integrated, generalized risk analysis methodology that can estimate accident-cause-specific hazmat transportation risk, accounting for various train and track characteristics, such as train length, speed, point of derailment, the number and placement of tank cars in a train, tank car safety design, and population density along rail lines. Using the two major causes of accidents on freight railroads-broken rails and track geometry defects-as an example, this paper demonstrates a step-by-step analytical procedure and decision support tool to assess how accident frequency, severity, and hazmat transportation risk vary by accident cause. The research method can be adapted for risk analysis at corridor- or network-level accounting for other accident causes.