Railway signals passed at danger: the drivers, circumstances and psychological processes.

A group of 34 drivers who had passed railway signals at danger was examined medically and questioned about the circumstances in which the signal had been passed. A conjectural explanation was formulated for each incident. Poor sight appeared to be a relevant factor in one case. Organic dementia, suspected but not confirmed, was possibly a factor in two cases. Three drivers were suffering from anxiety symptoms amounting to illness; in a further eight cases psychiatric symptoms not amounting to illness were regarded as relevant. There were special circumstances in three cases. Several psychological processes were thought to have played a part in causing the errors, and these are discussed under the headings: panic reaction, false expectations, preoccupation and distraction, responses to the wrong signal, relaxation after stress, and timing errors. It is argued that dangers arise from ergonomic faults, especially when drivers' efficiency has fallen off.