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Tracy Morgan speaks onstage at Spike TV's "Don Rickles: One Night Only" on May 6, 2014 in New York City.
Police officials say the truck driver who hit and critically injured comedian Tracy Morgan last weekend hadn't slept in more than 24 hours before the accident.
Morgan is still recuperating from that New Jersey car crash, which left one person dead.
Drowsy driving has sometimes been described just as dangerous as drunken driving, but unlike drunken driving, it can't be accurately tested for.
Dr. Charles Cziesler, professor of sleep medicine at Harvard Medical School, joins Take Two to explain the difficulties in punishing drowsy drivers, as well as talk about who is most likely to fall asleep behind the wheel.