Errors in motion processing amongst older drivers may increase accident risk

• Perceptual thresholds were measured using psychophysical procedures to allow precise measurement of perceptual degradation.
• We demonstrate that sensitivity to vehicle approach speed declines by nearly 3 mph for every decade in age.
• Older drivers over 70 years old may struggle to differentiate between speeds of 20 mph and 40 mph.
• The time available for older drivers to make a manoeuvre such as pulling out of a junction could be reduced by up to 50%.
• Age-related decrements in perceptual functions have implications for situations where gauging approach speeds are critical.

Accident statistics highlight that older drivers are more frequently involved in right-of-way collisions than younger drivers. Accurately gauging vehicle speed is critical for judgement of when to pull out from a junction safely in front of oncoming traffic. We used psychophysical methods to measure drivers’ ability to discriminate between different rates of looming presented by vehicles approaching at different speeds. We demonstrate that sensitivity to approach speed reduces by between 2.8 and 3.4 mph, dependent upon vehicle type, for every decade that age increases. We show that perceptual limitations for drivers over the age of 75 years can lead to a 50% reduction in time available to perform traffic manoeuvres, which may contribute in part to their overrepresentation in casualty statistics at junction. Results are discussed in terms of implications for road safety policy.