The effect of yellow light onset time on older and younger drivers’ perception response time (PRT) and intersection behavior

To understand why older drivers are over-represented in intersection crashes, this study sought to describe the intersection performance of older and younger drivers when traffic lights changed from green to yellow at the last second. Using a moderate-fidelity driving simulator, time to stop line (TSL) at yellow onset was manipulated as drivers approached intersections at 70 km/h (42 mph). Seventy-seven participants, approximately balanced for gender and age group, volunteered from the age categories of 18 to 24, 25 to 35, 55 to 64, and 65+. Driver decisions to stop or go were predicted using a logistic regression model with time to stop line as the single significant predictor. There were no age differences in perception response time (PRT). Older drivers approached intersections at a lower velocity and stopped more accurately than younger drivers. For those drivers who chose to go through the yellow light, speed profiles across the intersection and intersection clearance indicate that older drivers are more likely to be in the intersection when the light changed to red. A PRT of 1.0 s for yellow signal phasing was sufficient for all age groups.