Optimizing Railroad Tank Car Safety Design to Reduce Dangerous Goods Transportation Risk

This paper describes an optimization model developed to determine the most efficient way to enhance the safety design of tank cars used to transport toxic inhalation hazard (TIH) materials in North America and a quantitative risk analysis conducted to assess the risk and potential benefit of implementing enhanced safety-design tank cars. The conditional probability of release and the car's weight were used as the proxy for safety and cost, respectively. The concept of Pareto optimality is introduced to evaluate possible alternative tank car safety designs. A spatial analysis of the rail routes for TIH transport was conducted using geographic information system (GIS) data and software. The results were combined with probabilistic estimates of a release accident and the likelihood of exposure of the population along the routes. Risk profiles or “F-N curves” for both the baseline and alternate design tank cars are presented along with the corresponding risk reduction estimates. The results of this research were used by the Association of American Railroads in their development of new specifications for TIH tank cars, which are estimated to reduce the risk of rail transportation of these products by approximately 60 to 70 percent.