The Sleep Foundation points out that if the number of fatalities is closer to 6,000 annually, then drowsiness would make up about 21% of fatal car accidents. For comparison, the number of deadly accidents caused by drunk driving is around 30% of all fatal car crashes. 5 That's why most experts consider drowsy driving as dangerous as driving drunk.
In fact, studies show that drowsy drivers make similar mistakes to drunk drivers. People who drive tired show signs of cognitive impairment. Much like being drunk, drowsiness impairs decision-making, reaction time, and coordination, making those quick judgment calls drivers need to make in a hazardous situation more challenging.
The Sleep Foundation found that even minor sleep deprivation can impair a driver's cognitive reasoning.
One study concluded that "sleeping between six and seven hours a night doubled the risk of being involved in a crash while getting less than five hours of sleep doubled it again." 5