ABSTRACT
Crash statistics from state records are often considered the gold-standard in judging the on-road safety of older drivers in the US. However, it is becoming increasingly evident state records have limitations and that on-road tests can better capture the safety risk potential of older drivers. We examined performance metrics derived from an 18-mile on-road test in relation to functioning off-road in a large sample of 345 adults with common neurodegenerative diseases (N=160) associated with aging (e.g. Alzheimer's, Parkinson's and Stroke) and controls without neurodegenerative diseases (N=185). The measures of driver safety included overall safety errors, serious errors that could have resulted in crashes or near-crashes had the circumstances been different at the time they occurred, in addition to performance in essential driving tasks such as navigation to a specified destination and identifying landmarks while driving. Off-road functioning measures were derived from visual, motor and cognitive domains. The findings showed that adults with neurodegenerative conditions committed greater numbers of overall safety errors, serious errors, and performed more poorly in navigation and landmark tasks compared to control adults. Findings in the multivariate framework showed 405that differentiable components of cognitive functioning were relevant to on-road driver safety risk over and above disease status and age. For example, speed of processing, visuospatial construction were particularly relevant to overall and serious errors, while memory and vision were particularly relevant to navigation related secondary driving tasks. Those findings inform design of road tests for elderly and suggest that clinical assessments of driver fitness should consider several domains of off-road functioning.
