A new study indicates that a split sleep schedule is a better alternative than consolidated sleep during the day.

The study compared two 5-hour sleep periods, from 3 a.m. to 8 a.m. and from 3 p.m. to 8 p.m., to consolidated sleep periods at night and during the day.

Of the three, the 10-hour nighttime sleep was best, but the split schedule worked better than the 10-hour daytime schedule.

The study was prepared for the Federal Motor Carrier Safety Administration by sleep scientist Gregory Belenky of Washington State University.

Its purpose was to see if split sleep is as beneficial as consolidated sleep for driver safety, performance and long-term health.

The study may have implications for FMCSA's current sleeper berth rule, which industry interests contend is too restrictive.

The rule allows a split schedule but requires one period of at least 8 hours in the berth, and another of at least 2 hours. American Trucking Associations holds that this is too limiting.

"This new research report is the third study in the last five years to arrive at the same conclusion," said Dave Osiecki, senior vice president for policy and regulatory affairs at ATA, in an email response to a query.

"That is, drivers should be given greater flexibility in how they may rest using a sleeper berth. This latest report, four years in the making, is pretty clear on this point."

The study was conducted in a laboratory. The 53 volunteers simulated a 5-day workweek, sleeping then driving in a simulator, among other tests.

The researchers found that the nighttime sleep period provided the most sleep, about 8.4 hours, while the split sleep schedule provided 7.2 hours and the daytime schedule 6.4 hours. They found that the different sleep schedules led to no difference in performance of the required tasks, although sleepiness and blood chemical levels increased for the daytime sleepers.

"Results of this study suggest that when consolidated nighttime sleep is not possible, split sleep is preferable to consolidated daytime sleep," the researchers concluded.