Evaluation of Mitigation Strategies for High-Severity Derailments with Hazardous Materials

The transportation of hazardous materials (HAZMAT) by rail is a safe mode of transport and events with high-severity and/or high consequences from HAZMAT releases are rare. However, when high-profile events occur, they result in significant public pressure to modify the existing transportation practice and strengthen regulations to improve safety. The most recent example is the derailment on February 3, 2023, in East Palestine, Ohio that resulted in both a significant release HAZMAT and fires. As a result of the derailment, and subsequent National Transportation Safety Board and Federal Railroad Administration investigations, there is a renewed interest in evaluating and improving the safety of transporting HAZMAT in tank cars. The past regulatory responses to safety concerns for HAZMAT transport in railroad tank car safety have focused primarily on the tank car design and developed requirements for strengthening the tank shell. However, regulations that upgrade the tank structure are disruptive to the industry and expensive since it requires the replacement of a significant portion of the tank car fleet. This study investigates alternative mitigation strategies for high-severity railroad events involving HAZMAT transported in tank cars. In particular, the effects of the derailment speed on the release probability and consequences for tank car punctures are investigated. In addition, the effects of modifying the loading conditions to increase the outage volume (vapor space above the lading) are evaluated as a less costly alternative to increasing the tank car thickness to achieve an equivalent reduction in HAZMAT releases.