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Lack of sleep is dangerous, at least for drivers. A new AAA survey compares the risk to drunk driving. According to the AAA Foundation for Traffic Safety:

Experts recommend that healthy adults should sleep for at least 7 hours daily. The results of this study indicate that drivers who usually sleep for less than 5 hours daily, drivers who have slept for less than 7 hours in the past 24 hours, and drivers who have slept for 1 or more hours less than their usual amount of sleep in the past 24 hours have significantly elevated crash rates. The estimated rate ratio for crash involvement associated with driving after only 4-5 hours of sleep compared with 7 hours or more is similar to the U.S. government’s estimates of the risk associated with driving with a blood alcohol concentration equal to or slightly above the legal limit for alcohol in the U.S., and the increase in crash rate associated with driving after less than 4 hours of sleep is much greater.

More specifically, the effects are variable based on sleep levels:

Drivers who had slept for less than 4 hours, 4-5 hours, 5-6 hours, and 6-7 hours in the past 24 hours had an estimated 11.5, 4.3, 1.9, and 1.3 times the crash rate, respectively, of drivers who had slept for 7 hours or more in the past 24 hours. In an alternative analysis of drivers’ usual daily hours of sleep and sleep in the past 24 hours relative to their own usual amount of sleep, drivers who reported that they usually slept for 4-5 hours daily had 5.4 times the crash rate of drivers who reported that they usually slept for 7 hours or more; drivers who reported that in the past 24 hours they had slept for 1-2 hours less than usual, 2-3 hours less than usual, 3-4 less than usual, and 4 or more hours less than usual had 1.3, 3.0, 2.1, and 10.2 times the crash rate, respectively, of drivers who reported that they had slept for at least their usual amount. This study may underestimate the risk of driving while sleep-deprived, because data on crashes that occurred between midnight and 6 AM were not available, and other studies have shown that the effects of sleep deprivation on attention and performance are greatest during the early morning hours

Oddly, the foundation had no suggested solution to the problem.