The AAA Foundation for Traffic Safety in a new study says the number of drowsy driving crashes is eight times higher than federal estimates.

The foundation said its study is the most in-depth drowsy driving research conducted in the United States using in-vehicle dash cam footage of drivers’ faces in the three minutes leading up to a crash. The foundation said in a news release Thursday that it’s difficult to detect drowsiness following a crash, making it one of the most under-reported traffic safety issues.

The foundation analyzed footage from more than 700 crashes.

“Drowsy driving is a bigger traffic safety issue than federal estimates show,” said Dr. David Yang, executive director for the AAA Foundation for Traffic Safety. “Drivers who don’t get enough sleep are putting everyone on the road at risk. By conducting an in-depth analysis using video of everyday drivers, we can now better assess if a driver was fatigued in the moments leading up to a crash.”

The foundation said it measured the percentage of time a person’s eyes were closed and determined that 9.5 percent of all crashes and 10.8 percent of crashes resulting in significant property damage involved drowsiness.

Federal estimates indicate drowsiness is a factor in 1 to 2 percent of crashes.

The foundation said that in another survey, nearly all drivers (96 percent) said drowsy driving is a serious threat but 29 percent admitted to driving when they were tired to the point of struggling to keep their eyes open in the past month.

AAA said warning signs of drowsiness include having trouble keeping your eyes open, drifting from your lane and not remembering the last few miles driven.

“Don’t be fooled, the only antidote for drowsiness is sleep,” said William Van Tassel, manager of Driver Training for AAA. “Short term tactics like drinking coffee, singing, rolling down the window will not work. Your body’s need for sleep will eventually override your brain’s attempts to stay awake.”

AAA also recommends drivers travel at times of the day when they are normally awake, avoid heavy foods, avoid medications that cause drowsiness or impairment, schedule a break every two hours or every 100 miles, travel with an alert passenger and take turns driving, and take a quick nap at a rest stop to keep yourself alert.