Mitigating Strategies for Hazardous Material Trains: Evaluating the Risk Reduction

Abstract

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.

Validation of Methodology to Evaluate Risk Reduction in Tank Car Derailments

“…While it is difficult to make pile-up comparisons without detailed geometric data, it can be observed that the model faithfully represents the characteristic saw-tooth buckling and compact groupings as seen in the actual derailment. The combination of multiple close correlations between the pile-up configurations, the number of derailed cars, the number of punctures, and the distance travelled by the rear locomotive, provides confidence in the validity of the FRA modeling methodology 1 .…”

“…Prior work [1,2] developed a methodology to estimate the relative safety benefits (i.e., risk reduction) resulting from changes in tank car designs, braking systems, or operating conditions under derailment conditions, focusing on the likelihood of a tank to puncture (and thus release hazardous materials).…”