In Japan, drivers over the age of 65 years are classified as ‘older drivers’. On 1 October 2006, people over the age of 65 years comprised 20.8 per cent of the population, and 13.1 per cent of these are licensed drivers. Ageing causes a decrease in both physical and psychomotor abilities. Older drivers tend to cause traffic accidents owing to complex traffic conditions. The major goals of this study are to investigate the characteristics of older drivers' eye fixation movement and responses under heavy traffic volume at an intersection with a traffic signal. A personal-computer-based driving simulator was used to evaluate driver behaviours and to reproduce unexpected roadway hazards and realistic four-step traffic volume. An eye position recorder on a near-infrared system was used to collect eye movement data. The drivers' initial cognition ability was determined on the basis of reaction time tests under three different conditions. The older driver group in this study shows the following characteristics: first, as the task complexity increases, the reaction time increases (i.e. a slowed reaction); second, as the drivers become older, the time interval between recognition of a hazard and avoidance of the hazard increases; third, as the traffic volume increases, the driver has fewer eye fixations, shorter mean fixation time, and slower fixation speed compared with the younger drivers' group; fourth, traffic volume is one of the most important factors that complicates the driving task and causes hesitation in decision making. These results provide basic data to improve traffic services to make them suitable for older drivers in an ageing society.
