Vehicle accidents related to sleep: a review

Falling asleep while driving accounts for a considerable proportion of vehi cle accidents under monotonous driving conditions. Many of these accidents are related to work-for example, drivers of lorries, goods vehicles, and co mpany cars. Time of day (circadian) effects are profound, with sleepiness b eing particularly evident during night shift work, and driving home afterwa rds. Circadian factors are as important in determining driver sleepiness as is the duration of the drive, but only duration of the drive is built into legislation protecting professional drivers. Older drivers are also vulner able to sleepiness in the mid-afternoon. Possible pathological causes of dr iver sleepiness are discussed, but there is little evidence that this facto r contributes greatly to the accident statistics. Sleep does not occur spon taneously without warning. Drivers falling asleep are unlikely to recollect having done so, but will be aware of the precursory state of increasing sl eepiness; probably reaching a state of fighting off sleep before an acciden t. Self awareness of sleepiness is a better method for alerting the driver than automatic sleepiness detectors in the vehicle. None of these have been proved to be reliable and most have shortcomings. Putative counter measure s to sleepiness, adopted during continued driving (cold air, use of car rad io) are only effective for a short time. The only safe counter measure to d river sleepiness, particularly when the driver reaches the stage of fightin g sleep, is to stop driving, and-for example, take a 30 minute break encomp assing a short (<15 minute) nap or coffee (about 150 mg caffeine), which ar e very effective particularly if taken together. Exercise is of little use. Conclusions-More education of employers and employees is needed about plann ing journeys, the dangers of driving while sleepy, and driving at vulnerabl e times of the day.