Abstract
A study in Auckland, New Zealand compared 571 car drivers involved in killed or seriously injured crashes with 588 car drivers recruited while driving on public roads. There was a strong association between measures of acute sleepiness and risk of an injury crash. Significantly increased risk was associated with drivers who identified themselves as sleepy, with drivers who had had less than five hours of sleep the previous night, and with driving between 0200 and 0500h compared with other times of day. No increased risk was associated with measures of chronic sleepiness.