BALTIMORE (WJZ) -- Thousands die every year in truck accidents.
Many of those are the result of too many hours behind the wheel without time off for sleep.
But now, researchers think they've found a way to alert a driver when it's time to pull over.
Truck drivers like Frans Snijders probably see it most often, other trucks weaving on the road.
"They're driving six, seven hours," he says. "Then you get tired, then you see them going all the way on the road."
More than 4,000 Americans die every year in truck accidents, a third of them the result of driver fatigue.
Studies find 65 percent of truckers feel drowsy while driving, and nearly half say they've fallen asleep behind the wheel. British speech scientists say a driver's voice can reveal just how tired they are. They've developed an audio algorithm to extract information that reveals fatigue.
"We can see these very subtle changes that occur even within a day, even within one shift of work," says Mark Huckvale, of University College London.
They did it in phone calls every two hours to drivers working a mining site, finding changes in pitch, rhythm and the quality of a driver's voice as the shift went on.
They say it's possible the algorithm could someday be used by dispatchers making check-in calls to drivers.
"Perhaps the worst thing that could happen is the controller would say, 'Look you're sounding tired, we suggest you just stop and have a break for 30 minutes before you carry on,'" says Huckvale.
But taking a break isn't easy for drivers trying to meet a schedule.
"You don't have time to stop, take a nap and keep going," one told WJZ.
Federal rules, though, say truck drivers can spend no more than 11 consecutive hours behind the wheel and must stay off the road for 10 hours of rest.
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