Cognitive Functioning Predicts Driver Safety on Road Tests 1 and 2 Years Later


Address correspondence to Nazan Aksan, Department of Neurology, University of Iowa, Iowa City, IA 52242. E-mail:



To describe longitudinal changes in mean level and evaluate rank-order stability in potential predictors of driving safety (visual sensory, motor, visual attention, and cognitive functioning) and safety errors during an 18-mile on-road driving test in older adults and to evaluate the relative predictive power of earlier visual sensory, motor, visual attention, and cognitive functioning on future safety errors, controlling for earlier driving capacity.


Three-year longitudinal observational study.


Large teaching hospital in the Midwest.


One hundred eleven neurologically normal older adults (60–89 at baseline).


Safety errors based on video review of a standard 18-mile on-road driving test served as the outcome measure. A comprehensive battery of tests on the predictor side included visual sensory functioning, motor functioning, cognitive functioning, and a measure of useful field of view.


Longitudinal changes in mean levels of safety errors and cognitive functioning were small from year to year. Relative rank-order stability between consecutive assessments was moderate in overall safety errors and moderate to strong in visual attention and cognitive functioning. Although prospective bivariate correlations between safety errors and predictors ranged from fair to moderate, only functioning in the cognitive domain predicted future driver performance 1 and 2 years later in multivariate analyses.


Normative aging-related declines in driver performance as assessed using on-road tests emerge slowly. Even in the presence of conservative controls, such as previous driving ability, age, and visual sensory and motor functioning, cognitive functioning predicted future on-road driving performance 1 and 2 years later.