Falling asleep or being fatigued while driving is one of the most frequent causes of road crashes. The present paper is a review of research on incidence, precursors and consequences of driver sleepiness. About 10 % of Norwegian drivers report to have fallen asleep while driving during the last 12 months. About 8 % of injury road crashes are caused by a driver being fatigued or falling asleep. Estimates differ somewhat between studies and depend on type of accident. Sleep-related crashes are on the average more serious than crashes caused by other factors, due to the fact that they often occur under conditions of relatively high speed (e.g., rural roads with little traffic). The most frequent sleep-related crash type is driving off the road. Young, inexperienced males are more likely to fall asleep while driving. About 40 % of drivers involved in a fatiguerelated crash report some kind of sleep problem. Most drivers are aware of fatigue symptoms before falling asleep at the wheel, but some report having fallen asleep without noticing any early signs. Most drivers know that stopping to have a nap is the most efficient countermeasure when feeling sleepy during driving, but few drivers actually do this.
Keywords: driver fatigue; road safety; sleep; hypovigilance; crash risk