Nearly one-third of American motorists admit they have driven while practically falling asleep within the last month, despite the fact that 96 percent say they consider so-called “drowsy driving” unacceptable, according to a new survey from the AAA Foundation for Traffic Safety.

Officials with the nonprofit research and education organization said survey results show many drivers fail to act in accordance with their views and commonly underestimate the dangers posed by sleepiness behind the wheel.

Man asleep in car

“Drowsy driving kills, just as sure as drunk, drugged and distracted driving does,” Peter Kissinger, the foundation’s president and chief executive officer, said in a news release. “Drivers have a tendency to underestimate the impact being tired has on their driving ability, which puts themselves and others at risk.”

The survey found that, while 56 percent of people described sleepy drivers as a very serious safety threat, 32 percent said they had driven within the past month despite having difficulty keeping their eyes open.

The results bolster earlier foundation research on the subject. A 2010 report found that 41 percent of motorists admitted to having nodded off or fallen asleep while driving at least once in their lives, and 11 percent said they had done so within the past year.

Fifty-two percent of men reported having fallen asleep behind the wheel at some point, compared with 30 percent of women.

According to the National Highway Traffic Safety Administration (NHTSA), drowsy driving contributes to more than 100,000 crashes, 40,000 injuries and 1,550 deaths a year.

But safety officials say the damage may be even greater because driver fatigue is actually underreported as a cause of vehicle crashes.

NHTSA officials say driver sleepiness leads to slower reaction time, reduced vigilance and slower information processing.

The federal agency says those most likely to drive despite drowsiness are male drivers from 16 to 29, people who work at night or put in long or irregular hours on the job and people with untreated sleeping disorders.

Last year’s report from the AAA Foundation found that two-thirds of motorists involved in drowsy driving crashes were men. And drivers from 16 to 24 were nearly twice as likely as those 40 to 59 to be involved in such an accident.

Those findings support views within the insurance industry, which has long considered teens a greater risk than other drivers to cover because of their propensity to become distracted or engage in other unsafe behaviors behind the wheel that can lead to accidents. That is the main reason it can be a challenge for families nationwide to find affordable.

Researchers found that having a passenger in the car may reduce a motorist’s risk of crashing as a result of tiredness. According to the report, vehicles with at least one passenger were nearly 50 percent less likely to be involved in a crash related to drowsiness.

Safety officials say steps exist through which motorists can reduce their risks, including planning to get enough sleep, not drinking even small amounts of alcohol when tired and limiting driving between midnight and 6 a.m.

Motorists who become sleepy should stop driving immediately and either let a passenger drive or get some sleep before returning to the road. A 20-minute nap and a couple cups of coffee may also help keep drivers alert, but efforts such as opening a window or listening to the radio have not been shown to be effective.