Visual motion contrast thresholds in the periphery predict older drivers' behavior at intersections

Peripheral motion contrast sensitivity decline is likely due to a progressive dysfunction of the magnocellular pathway in the aging brain. Previous research from our group had demonstrated that the Peripheral Motion Contrast Threshold 2-minute test version (PMCT-2) predicts older drivers' hazardous behaviors in simulated driving environments. This study extends this work by examining correlations between PMCT-2 scores and on road driving outcomes at intersections coded from video recordings of fifty older drivers (65-89) navigating predefined urban routes in their own vehicles. We found significant correlations between PMCT-2 and scanning errors at non-signalized and stop-signalized intersections. We also found significant PMCT-2 correlation with driving compliance errors, notably incomplete stops, which was further supported by single-predictor regression using heteroskedasticity-robust estimation. Multiple linear regression analyses further showed that PMCT-2 remained the only significant predictor of stop-sign compliance errors after adjusting for age, gender and scanning error rates at stop signs. In contrast, its relationship with scanning errors was attenuated in linear models, reflecting the very low frequency of scanning errors observed on the road. These findings build on prior evidence that the PMCT-2 predicts older drivers' performance outcomes and, for the first time, demonstrate its potential to predict actual on-road driving performance at intersections.