The safety of hydrogen as a locomotive fuel was assessed to estimate how often hydrogen leaks could contribute hazards to rail incidents. Event sequence diagrams were used to describe possible accident scenarios and progressions. Initiating event frequencies and branch event probabilities for each scenario were quantified with uncertainty using probability distributions fit to Federal Railroad Administration and U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration data on applicable incidents. These incidents included on-rail collisions, derailments, collisions with vehicles at grade, and fires/explosions. Uncertainty was propagated through the event sequence diagram to estimate the frequency and conditional probability of accident end states. The analysis identified two higher-frequency scenarios where hydrogen is expected to significantly increase consequence severity. These scenario outcomes resulted from collisions and included overpressure or jet fire events. These scenarios involved subsequent immediate or delayed hydrogen ignition, as well as jet fires or pressure bursts resulting from fire/explosion initiating events which affect the tank. Delayed and immediate hydrogen ignition probabilities were identified as being highly uncertain and yet critical for improving accuracy in the predicted frequencies for these two scenarios.