The relative importance of a variety of human factor variables to driving performance was investigated using a representative samples of 60 drivers. Factors considered included: visual and perceptual abilities, risk taking, reaction time measures, biographical, attudinal and personality variables and physiological measures of stress. Driving performance was assessed by obtaining accident and exposure histories for the previous 3 years and also by considering the number of driving errors committed on a test drive. In the analysis special attention was given to identifying any age differences revealed by the results that might help to explain why accident rates vary with age. Results indicated that the variable measuring risk taking was most highly correlated with driving performance. Additional variables that were significantly correlated with driving performance included; age, socioeconomic group number, annual kilometers driven, additional driver training, one personality factor and physiological measure of stress. Several of variables showed significant age effects