A 2-year study of older drivers was conducted at the University of Nebraska to develop and evaluate methods for improving the safety of older drivers. During the first year, data on several characteristics including driving performance of older drivers were collected. The correlation between driving performance and measured characteristics was investigated to provide a basis for the design of the countermeasures, which were evaluated in the second year. The results of the analysis of the factors associated with the driving performance of older drivers are presented. Several factors relative to the physical and mental status of 105 drivers between the ages of 65 and 88 were measured. In addition, their driving knowledge and on-street driving performance were evaluated. Pearson product-moment correlation coefficients were computed to measure the relationships between on-street driving performance and the other factors. In addition, stepwise multiple regression analysis was used to determine the combination of factors that accounted for the most variability in the on-street driving performance. A number of factors associated with vision, visual perception, cognition, and driver knowledge were found to correlate significantly with the driving performance of older drivers. The results of the analysis suggest that a number of methods can improve the safety of older drivers; among them are (a) physical therapy to improve range of motion,(b) therapies or exercises to improve visual perception and cognition, and (c) driver education to increase driving knowledge pertinent to the accident situations in which older drivers are overinvolved.