A questionnaire study was conducted to obtain information from shiftworkers on the levels of tiredness experienced on the drive to and from work at different times of the day. The results demonstrated that, compared to non-shiftworkers, shiftworkers were more tired on the drive between their home and the workplace and more at risk of falling asleep behind the wheel. The main factors contributing to this increased level of sleepiness and associated driving impairment were the length of the sleep period prior to work, the type of shift and the travelling time. There was some evidence to suggest that on working days shiftworkers were more likely to be involved in an accident than non-shiftworkers. However, there were insufficient data to determine whether accidents were correlated with driver sleepiness.