Some of the scientific evidence used to justify changes in the 34-hour restart provision is being questioned by the trucking industry.

The Federal Motor Carrier Safety Administration is relying in part on a two-part study conducted at Washington State University to say that the 34-hour restart should include two nights of rest.

The first part, done for FMCSA by Hans Van Dongen and Gregory Belenky of the Sleep and Performance Research Center at Washington State University, found that the 34-hour restart gives daytime drivers a chance to catch up on their rest, but it does not work as well for night drivers. (See "Fatigue Study Provides Basis for 34-Hour Restart Proposal," 1/28/2011.)

The second part, also done by Van Dongen and Belenky, found that the effectiveness of the break was improved by adding an additional nighttime sleep period.

American Trucking Associations, which opposes the restart provision along with the rest of the proposal, plans to take issue with the agency's use of these studies.

"It is a stretch for FMCSA to rely on this study to make policy," said David Osiecki, senior vice president for policy and regulatory affairs at ATA.

The second part of the study has not yet been published or peer-reviewed (it will be soon, says FMCSA), yet it is the basis for the agency's proposal for two nights of rest in the restart, Osiecki noted.

The study relies on a laboratory test of just 12 people. "That's clearly not representative, especially in light of the author's recommendation for FMCSA to conduct a validation study using actual truck drivers operating in the real world," Osiecki said.

Osiecki was referencing a recommendation in Phase II that reads, "validation of the study findings in a sample of CMV drivers in a real-world field study is important."

The first phase of the test used 27 people, but none of the people in either phase were professional truck drivers.

Defending the Study

This does not mean the study is not valid, said author Hans Van Dongen. He confirmed that the results can be considered valid because he was able to control the variables in the laboratory setting and he was measuring human response rather than occupational response.

Van Dongen noted that the research subjects were healthy young adults with no sleep disorders, which made for a stronger finding that the restart is ineffective.

"Had we studied a sample of patients with sleep apnea - widely reported to be a common sleep disorder among CMV drivers - or other medical conditions, the expected performance deficits in the worst-case condition would have been greater still," the study says.

Still, there is evidence that older, seasoned professionals may outperform younger drivers, says Ron Knipling, a former research scientist at the Virginia Tech Transportation Institute and author of a textbook on truck safety.

Knipling cited an old (1994) National Highway Traffic Safety Administration study that found younger drivers more likely to have problems with drowsiness than older ones. And the more recent Large Truck Crash Causation Study found that 67 percent of drivers judged "fatigued" were 40 or younger, versus 56 percent of those not "fatigued."

"That doesn't sound like a big difference, but it works out to a 1.6 odds ratio for being fatigued, given being 40 or under versus being 41 or older," he said.

This may be explained by self-selection among those who become truck drivers, Knipling surmised. "In spite of the health disadvantages (truck drivers) clearly have, I don't think an 'average' person could do the job as well," he said.

What FMCSA Says

The agency itself is open about the shortcomings of the second phase of the study.

"It utilized a very small sample size (12 drivers)," the agency says in its proposal. "Also, the study took place not on the road, but in a laboratory setting with participants who knew that their behavior was being observed.

"In addition, the participants were instructed to sleep and were all recruited as perfectly healthy drivers. Because the study included a 58-hour restart time, not a 34-hour restart, the improvements could have been attributable to the extra off-duty period these 12 drivers were getting. In reality, drivers are not always in perfect health, and they cannot be told to sleep at a particular time by FMCSA."

All of that said, the agency found the evidence for the two-night requirement persuasive.

"FMCSA believes that the two phases of this study plus (other research) justify (the) proposal to amend the 34-hour restart by expanding the required restart period and adding a requirement for two off-duty periods from midnight to 6 a.m.," the agency said in its proposal.

In proposing the two-night requirement, the agency said it has stuck by the 34-hour restart in past versions of the rule because it provides productivity benefits and it believed that drivers would not use the provision to work extreme hours. "The agency assumed that drivers would use the restart mainly to simplify bookkeeping and to limit down-time while away from home."

Now the agency says that it learned during the listening sessions last year, and from comments in the docket, that drivers and carriers do use the 34-hour restart as a minimum. Drivers who are on the road for weeks at a time could work very long hours, and some carriers with regular schedules say they use the restart to add one work shift a week.

"If carriers have arranged their schedules so that drivers are on duty for the full 14-hour day, as ATA claimed in its 2010 comment to the docket, then the restart allows a driver to work more than 80 hours in 7 days compared with 60 hours in the pre-2003 rule."

The agency said it continues to believe the 34-hour restart is a sensible way to let drivers spend less idle time on long runs, but it must balance this against the risk that the restart may be exacerbating problems with long hours and resulting fatigue.

Ultimately, the issue could be decided by a panel of appeals court judges. ATA has indicated that unless this and other provisions of the agency's proposal are changed in the rulemaking process, it is likely to take the matter to court.

Story corrected 2:40 p.m. 2/2/2011 to correct the University of Washington in the first paragraph to Washington State University. We regret the error.