There is a significant increase in the transportation by rail of hazardous materials such as crude oil and ethanol in the North American market. Several derailment incidents associated with such transport have led to a renewed focus on improving the performance of tank cars against the potential for puncture under derailment conditions. Proposed strategies for improving puncture resistance have included design changes to tank cars, as well as, operational considerations such as reduced speeds. Given the chaotic nature of derailment events, it has been difficult to quantify globally, the overall ‘real-world’ safety improvement resulting from any given proposed change.
A novel and objective methodology for quantifying and characterizing reductions in risk that result from changes to tank car designs or the tank car operating environment is outlined in this paper. The proposed methodology captures several parameters that are relevant to tank car derailment performance, including multiple derailment scenarios, derailment dynamics, impact load distributions, impactor sizes, operating conditions, tank car designs, etc., and combines them into a consistent probabilistic framework to estimate the relative merit of proposed mitigation strategies.