Analysis of Restricted-Speed Accidents Using Fault Tree Analysis

Restricted speed is the speed that permits stopping within one-half the range of vision, normally not exceeding 20 miles per hour. The occurrences of some severe accidents at restricted speeds have highlighted the importance of safety improvements in restricted-speed operations. The Federal Railroad Administration (FRA) has identified restricted-speed violations as a common rule compliance problem. Nevertheless, little prior research has been conducted on the analysis of train operations and safety risk under restricted speeds. This paper used Fault Tree Analysis to explore scenarios for restricted-speed operations to identify failure paths that lead to train accidents. Understanding restricted-speed train accident causal chains and corresponding structural representations of relevant contributory precursors can contribute to more accurate estimation of restricted-speed risk. Four recent restricted-speed accidents were studied based on the information from the National Transportation Safety Board (NTSB) and FRA. This study may serve as a reference leading to the further development of quantitative risk assessment and the evaluation of risk mitigation strategies for restricted-speed operations.