The Sensitivity and Bias of Older Driver Judgements in an Arrival-Time Task.
A signal detection theory approach was adapted to an arrival-time task to establish the sensitivity and bias of traffic judgements. The factors of age, gender and vehicle approach speed were examined with 20 older drivers (over 70 years of age) and 20 younger (24-39 years) experienced drivers. A disappearance paradigm was generated using digitally edited video sequences of a vehicle approaching a stationary observer. The vehicles were travelling at 44km/h, 58km/h or 72km/h and vanished at a constant distance. Participants gave a rating of confidence on a five point scale from totally confident that the vehicle would have reached a white target line, to totally confident the vehicle would NOT have reached the target, and provided an estimate of the vehicle's speed. Older drivers demonstrated a diminished sensitivity when estimating the arrival-time of approaching vehicles in comparison to younger experienced drivers. A reduction in sensitivity to the higher approach speed was found for all driver groups. A conservative bias of older drivers was confirmed in the 44km/h approach condition but not the 72km/h condition. Older females demonstrated the most risky combination of low sensitivity and less conservatism at the highest approach speed. These results are used to clarify previous findings and the implications for accident risk of each driver group are discussed.