Driver sleepiness.
Falling asleep at the wheel accounts for a sizeable number of vehicle accidents under monotonous driving conditions. The risk of driver death and serious injury is high. Circadian factors are profound and seem to be of equal (if not more) importance to the duration of the drive. Unfortunately, only the latter tends to be built into legislation. Young adults are the most likely to have these accidents, especially in the early morning, whereas older adults may be more vulnerable in the early afternoon. Drivers falling asleep are unlikely to recollect having done so, but they are aware of the precursory state of feeling sleepy, as normal sleep does not occur spontaneously without warning. Self-awareness of sleepiness is a better method for alerting the driver than in-car automatic devices. Car simulator studies show high inter-correlations between driving performance, EEG measures of drowsiness and self-assessments of sleepiness. Putative countermeasures to sleepiness during continued driving (for example cold air, playing car radio) have to be substantiated. The only safe countermeasure is to stop driving. At this point, a nap and/or coffee (caffeine) can be effective. Exercise is of little use. More driver education is needed about the dangers of driving whilst sleepy.