
Quoting
FAQs: Drowsy Driving
On the national level, the National Highway Traffic Safety Administration (NHTSA) conservatively estimates that 100,000 police-reported crashes are the direct result of driver fatigue each year, resulting in an estimated 1,500 deaths, 71,000 injuries, and $12.5 billion in monetary losses. However, it is very difficult to determine when fatigue causes or contributes to a traffic crash, and many experts believe these statistics understate the magnitude of the problem.
On the individual level, driving while tired is very dangerous, because a driver who falls asleep may crash head-on into another vehicle, a tree, or a wall, at full driving speed, without making any attempt to avoid the crash by steering or braking.
The inability of a sleeping driver to try to avoid crashing makes this type of crash especially severe. Some studies have found people's cognitive-psychomotor abilities to be as impaired after 24 hours without sleep as with a BAC of 0.10%, which is higher than the legal limit for DWI conviction in all US states.
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In fact, drowsy drivers sometimes drive so poorly that they might appear to be drunk. In a survey of police officers conducted by the AAA Foundation for Traffic Safety, nearly 90 percent of responding officers had at least once pulled over a driver who they expected to find intoxicated, but turned out to be sleepy (and not intoxicated).