The influence of cognition and age on accommodation, detection rate and response times when using a car head-up...

Car head-up displays (HUDs), which portray information in the form of a virtual image reflected off a combiner, allow the viewing of complex information, such as route guidance, without the need for the driver to look away from the road ahead. The cognitive demand required by the HUD task may distract drivers from the outside world scene and cause reaction times to slow. Cognitive capacity also decreases with age. The aim of the present study was to determine the effect of cognitive demand and age on the use of a car HUD. Subjects (young, middle or older age drivers, each group n = 8) performed a HUD-assisted driving task, with three levels of cognitive demand, whilst accommodation was simultaneously measured using a dynamically recording infra-red optometer. Response times to, and the detection rate of, changes in both the HUD image and the outside world scene were analysed. Increasing the cognitive demand associated with the HUD image increased over-accommodation (greatest in the young, 0.34 +/- 0.05 D, p < 0.001). Response times to and detection of changes in the HUD image and outside world scene were significantly worse with increased cognitive demand. Response times to and detection of changes in the HUD image and outside world scene also increased with age. The implication of the results with respect to car HUD design and safety are discussed.