Driving while drowsy - and the fatal accidents it causes - has increasingly drawn national attention in recent years.

Federal regulations scheduled to take effect by July 1, 2013, will attempt to keep truck drivers from getting tired and overworked:

-- The maximum number of hours a driver is allowed to work in a week has been decreased from 82 to 70.

-- Truck drivers must take a 30-minute break after driving eight straight hours.

-- Truck drivers who reach the maximize weekly work hours must rest at least two nights when their 24-hour body clock demands sleep the most, from 1 to 5 a.m. This is part of a rule that allows a driver to rest for 34 hours to "restart" their body clock every seven days.

-- A driver is permitted to be on the road up to 11 hours a day, including breaks, but the Department of Transportation's Federal Motor Carrier Safety Administration is researching the risks of driving for this amount of time.

-- Trucking companies that let their drivers exceed the 11-hour driving limit by three or more hours could be fined $11,000 per offense, and the drivers could face penalties of up to $2,750 for each violation.

In announcing the rule changes, Transportation Secretary Ray LaHood said, "Trucking is a difficult job, and a big rig can be deadly when a driver is tired and overworked. This final rule will help prevent fatigue-related truck crashes and save lives. Truck drivers deserve a work environment that allows them to perform their jobs safely."

Mark Rosekind, a member of the National Transportation Safety Board, called the revision "the most science-based rule that has ever been seen."

"There's 50-plus years of good science now about the need for sleep and physiological disorders related to fatigue," he said. "This rule reflects a lot of that science."

Trucking organizations opposed the rules when they were revised late last year, viewing them as a restriction on drivers.

But Rosekind said the rules were not strict enough. He said companies should be required to ask their employees if they have sleep disorders, install electronic devices in trucks to monitor drivers' hours and provide programs that educate drivers about fatigue.

Stephanie M. Lee is a San Francisco Chronicle staff writer. E-mail: slee@sfchronicle.com Twitter: @stephaniemlee