Most safety problems posed by truck driver fatigue can be solved through a combination of education, technology and changes in scheduling, said a leading expert in sleep disorders.

But David F. Dinges, associate professor of psychiatry at the University of Pennsylvania, said Tuesday that despite a five-year, $4.5 million study on driver fatigue due out this fall from the Federal Highway Administration, more work is needed to determine the extent of the problem.Mr. Dinges, who also sits on the American Trucking Associations Foundation's medical advisory board, said that what experts know about sleep and fatigue problems is outweighed by what they don't know.

He said technology can now measure everything from the number of times drivers blink or turn the wheel, to their brain waves and heart beats, but it is not certain which is the most effective measure of fatigue.

"There's more media coverage than substantive dollars put forth on this issue," he said. He said that estimates from different federal agencies range

from fatigue playing a role in 1 percent to 2 percent of fatal truck accidents to as high as 30 percent to 40 percent.

"I believe there is a significant amount of sleepiness-related accidents and near misses out on the highways," he said. "Even if the numbers are 5 percent, that's substantial." There are more than 3,000 fatal accidents involving heavy trucks annually.

The problem is one that trucking officials say they have trouble getting a handle on as well.

"One of the problems is what's really fatigue, what's boredom," said Joe Mack, training director in the safety department of Werner Enterprises Inc., the Omaha truckload carrier. "Did he fall asleep and run off the road, or did he start spacing out and day dreaming?"

Mr. Mack said that only one accident at Werner in the past two years was definitely due to driver fatigue. And he believes that current regulations that order a driver to be off for eight hours after a 10-hour shift can cause more fatigue problems by disrupting normal working and sleep patterns.

Driver fatigue was classified as the No.1 safety problem in trucking by a summit of government, safety and industry officials that met in Kansas City in March.

The ATA agrees that driver fatigue is a serious problem, and it's participating in the FHWA study.

But the ATA officials are concerned that some proposals about changing hours of service or restricting what hours of the day truckers can operate would create economic problems for the truck industry without solving the fatigue problem.

"The most dangerous thing in the world is to let these people out at night doing their own study, writing press releases about what they think they found," said Thomas Donohue, president of the ATA, when asked last week why the ATA was involved in the study at this time. "Quite frankly, I want to beat them to the punch. I don't want them to define the agenda."