Multivariate analysis of age-related driver ability and performance deficits.

A computerized measure of 22 visual, attentional, perceptual, cognitive and psychomotor abilities and a structured road test were administered to 407 elderly drivers age 62 and above. Approximately two-thirds of the sample had been referred to licensing agencies on the basis of observed unsafe incidents and the remainder were volunteers free of reported incidents. Significant correlations (r = 0.4-0.5) were found between unsafe driving incidents and deficiencies in attentional, perceptual, cognitive and psychomotor categories and 0.3 for the visual. A total score based upon all ability measures correctly identified 80% of incident-involved, while misidentifying only 20% of the incident-free drivers. Unsafe driving incidents evidenced significant but small positive correlations (r = 0.1-0.2) with road test errors indicative of skill deficiencies but not with errors in routine safe driving practices. Substantial examiner differences attenuated relationships involving road performances, and correlations with skill-related performances rose (r = 0.2-0.3) when these effects were partialled out. Intercorrelations among measured abilities were high, indicating the need for caution in interpreting reported relationships between individual abilities and unsafe driving incidents. The authors also caution against interpreting correlations found in highly selected samples as representing the magnitude of relationships in the population at large.