Drawing Attention to the Risks of Drowsy Driving

When it comes to drowsy driving dangers, the National Transportation Safety Board said today that Americans need to wake up.

The NTSB, for the first time, held a forum on drowsy driving in Washington, D.C.

Mark Rosekind, a board member, said one of the biggest problems is that people underestimate just how tired they are.

"Humans are just horribly inaccurate if we have to self-diagnose fatigue," Rosekind said. "That's what allows us to put ourselves in life-threatening situations."

According to the AAA, 40 percent of drivers have admitted to falling asleep at the wheel.

Losing two hours of sleep in just one night can affect a person's reaction time by 20 percent, the NTSB said.

All that can add up to one of the most under-reported problems on the road. One study has suggested that 20 percent of crashes - one out of every five accidents - involves a tired driver.

On test tracks at Virginia Tech, researchers are assessing drivers for alertness and signs of fatigue.

Cameras are also being tested to see whether they can look at a person's face and find telltale signs of a lack of sleep. Some cars have even been equipped with technology that can sense a driver drifting into another lane.

For now though, the NTSB is issuing this bit of advice: If a driver has not had enough sleep, they should not get behind the wheel.

ABC News' David Kerley and Matt Hosford contributed to this report.