Exploring the psychological factors involved in the Ladbroke Grove rail accident.

Ten years after the event and the question as to exactly why a driver passed a signal at danger to cause the Ladbroke Grove rail disaster is still an open one. This paper uses the literature on human error and cognition, combined with critical path analysis, to provide further insight. Five aspects of train operation are drawn out of the known facts surrounding the incident: custom and practice in the use of the Driver's Reminder Appliance, operation and use of the Automatic Warning System, the sequence of signalling information, methods of supplying route information, and speed restrictions. Associated with each are several important human factors issues which, combined, give rise to five potential explanations. Critical path analysis is used to map these explanations onto the known facts of the situation. It is suggested that the proximal cause of the Ladbroke Grove rail crash was a combination of an association-activation error and a mode error (leading the driver to mistakenly assume he had activated the Reminder Appliance) together with a loss-of-activation error (the driver failing to remember that a previous signal was showing caution) and a data-driven-activation error (by associating an in-cab warning to the wrong external source). The findings support the original inquiry recommendations, but also go further into predictive methods of detecting problems at the human/transport system interface.