The Sensitivity and Bias of Older and Younger Driver Judgments in Complex Traffic Environments.
A previous investigation adapted a signal detection theory approach to an arrival-time task to establish the sensitivity and bias of traffic judgements. It was demonstrated that older drivers generally have a diminished sensitivity to the arrival-time of approaching vehicles. The conservative estimations of older drivers were also attenuated in response to faster speeds. These findings were demonstrated under simplistic single vehicle approaches of varying speed. Under the age complexity hypothesis, it was exp ected that an increase in the complexity of the traffic environment would further reduce the sensitivity of older driver judgements. Twenty-four older drivers (71-82 years) and 24 younger experienced drivers (24- 42 years) were presented with digitally edited video sequences of two approaching vehicles that disappeared at a constant distance. The three combinations of the two vehicles' speeds were 44km/h - 72km/h, 58km/h - 72km/h, and 58km/h - 86km/h. Order of speed presentations and lane positions were counterbalanced. Participants indicated, for each vehicle in turn, whether it would have reached a target line on the road when a car horn sounded. Preliminary analyses indicate that older drivers have a significantly degraded sensitivity to the arrival-time of two approaching vehicles in comparison to younger drivers. Lower levels of sensitivity were demonstrated in the higher velocity conditions and the conservatism of older drivers in particular, was reduced for higher speed presentations. These results confirm the difficulties of older drivers in response to more complex environments and implicate speed as a factor in traffic judgment errors.