Predicting the Effects of Disability Glare on Driving Performance

A driving simulator was used to investigate the effects of simulated glare from the sun on the execution of left-turns at an intersection. The presence of glare resulted in a significant reduction in the safety margin used by drivers (by 0.65 sec on average). The effect of glare was larger for low-contrast than for high-contrast oncoming vehicles. Older drivers (45-60 years) had a significantly greater reduction in safety margin compared to younger drivers (19-29 years), however, there was large inter-driver variability in both age groups. Older drivers adopted a larger safety margin in non-glare conditions with the result that the net effect of glare on driving safety was the same for both age groups. It is proposed that the reduction in retinal image contrast caused by glare caused drivers to overestimate the time to collision with oncoming cars.