Abstract
It has been shown that car drivers under 25 years incur a higher proportion of their casualties during the hours of darkness than do older drivers. This arises from corresponding difference in the amounts of travel during the dark hours . If the distance driver by young drivers were distributed over the day in the same way as for older drivers, their casualty-rate would be about 9 per-cent lower, but still more than 2« times the rate of older drivers.