Accident Details
Domain: Rail
Year: 1989
Data Categories: Dynamic
Properties Lost: Integrity, Completeness, Accuracy, Timeliness, Verifiability, Fidelity / Representation, Lifetime
Summary:
Criticality of train weight not recognized, resulting in multiple fatalitiesDetails:
In May 1989 a Southern Pacific Transportation Company freight train derailed in San Bernardino, California. The train derailment accounted for seven fatalities and two serious injuries; however, that accident also damaged a fuel pipe and less than a fortnight later it ruptured causing a further two deaths and three serious injuries.
One of the causal factors of the train’s derailment, as reported by the National Transportation Safety Board, was a “failure to determine the weight of the train” and in summary, the operator thought it weighed less than it actually did, resulting in the dynamic braking being insufficient to deal with the downhill gradient it was travelling on. The Company had used a computer to determine the train’s weight and because the actual weights had not been entered the system made its calculations based upon estimated weights, which were lower. Clearly this was not a systematic failure of the computation algorithm but again potentially a failure to appreciate the criticality of the weight information and its potential as a causal factor within an accident sequence.
From the criticality of the weight information, derived safety requirements could be developed for the various data sources that were used to derive the weight. Such requirements could be expected to highlight the properties of Integrity, Completeness, Accuracy, Timeliness, Verifiability, Fidelity / representation and Lifetime.