White Paper: Consequences of Drowsy Driving

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body has built-in mechanisms to ensure we get that sleep, including a biochemical means of tracking how much time we spend sleeping or being awake. When a sleep debt builds up, this biochemical tally triggers excessive sleepiness and the urge to sleep. In addition, natural circadian rhythms make us more likely to feel drowsy in the dark early hours of the day. This critical time of sleepiness occurs even if we get adequate sleep. (NHLBI, 2005) This peak in sleepiness corresponds to the number of sleep-related automobile accidents that occur in the early morning hours. (Pack et al 1995)

The sleep-wake cycle is inevitable. Although we can deny or mask the physiologically based urge to sleep, our sleepiness will become apparent when we are conducting monotonous tasks, such as driving on a monotonous highway. The boring task often does not cause fatigue as much as reveal or unmask underlying sleepiness. (Roth et al, 1994; NTSB 1995)

Studies have linked sleepiness and fatigue to decreases in vigilance, reaction time, memory, psychomotor coordination, information processing, and decision making, all of which are needed for safe driving. (Lyznicki et al, 1998) Sleepiness can impair driving performance as much or more so than alcohol, studies show. The effects of sleepiness on driving performance are akin to that of a blood alcohol concentration close to that of the legal limit in most states in a well-rested person. (Dawson and Reid, 1997; Powell, 2001) In other words, driving sleepy is like driving drunk. Sleepiness not only causes people to fall asleep at the wheel, but also triggers repetitive head drops due to microsleeps of a few seconds in duration. (Powell and Chau, 2010)

Awareness of drowsy driving
Although people who fall asleep for more than a few minutes are often aware of those lapses in wakefulness, drivers may not be aware of shorter lapses and microsleeps, which can also have serious consequences when a quick reaction is needed to avoid high-speed crashes. (Powell and Chau, 2010) Most people also are not aware of how drowsiness affects their driving performance, even without falling asleep. Studies also suggest