A survey of 3686 drivers in Ontario has provided data on time behind the wheel as well as the distances driven for licensed drivers in six age groups, both sexes, and three regions. Substantial differences were found in times, distances and average speeds. Men drove 50% greater distances, but spent only 30% more time driving than women;​ older drivers drove at lower speeds than younger drivers. Such differences in speed affect comparisons of accident rates, whether based on units of time or distance, and affect perceptions of high risk among different groups of drivers. A definition of exposure to risk of road crash is required which considers both time and distance appropriately.