Recent deadly crashes involving large interstate buses like the one involved in a fatal crash in Virginia two weeks ago have heightened concerns about driver fatigue.
Four women were killed and dozens injured when authorities say the driver for a discount service dozed off as the bus carrying 59 passengers barreled northward on Interstate 95.
The bus headed from North Carolina to New York overturned when the driver awoke and tried to swerve back onto the road.
Thirty-seven-year-old Kin Yiu Cheung is charged with four counts of involuntary manslaughter.
Sleep scientists, safety advocates and labor leaders say the roots of the accident lie with an industry whose economic model often results in drivers on the road with too little rest and at hours when their bodies naturally crave sleep.