Drivers who miss one to two hours of the recommended seven hours of sleep in a 24-hour period nearly double their risk for a crash, according to new research from the AAA Foundation for Traffic Safety.

The Centers for Disease Control and Prevention says that 35% of U.S. drivers sleep less than the recommended seven hours daily. With drowsy driving being involved in more than one in five fatal crashes on U.S. roadways each year, AAA is warning drivers of the potential consequences of getting less than seven hours of sleep.

“You cannot miss sleep and still expect to be able to safely function behind the wheel,” said Dr. David Yang, executive director of the AAA Foundation for Traffic Safety. “Our new research shows that a driver who has slept for less than five hours has a crash risk comparable to someone driving drunk.”

The foundation’s report, Acute Sleep Deprivation and Risk of Motor Vehicle Crash Involvement, reveals that drivers who miss two to three hours of sleep in a 24-hour period more than quadruple their risk of a crash compared to drivers who get the recommended seven hours of sleep. This is the same crash risk that the National Highway Traffic Safety Administration (NHTSA) associates with driving over the legal limit for alcohol.

The AAA Foundation report found that in a 24-hour period, crash risk for sleep-deprived drivers increased steadily when compared to drivers who slept the recommended seven hours or more:

• Six to seven hours of sleep: 1.3 times the crash risk
• Five to six hours of sleep: 1.9 times the crash risk
• Four to five hours of sleep: 4.3 times the crash risk
• Less than four hours of sleep: 11.5 times the crash risk

The report is based on analysis of a representative sample of 7,234 drivers involved in 4,571 crashes. All data are from NHTSA’s National Motor Vehicle Crash Causation Survey.

The AAA Foundation report is available here.