With Congress up against a December 11 deadline to pass an appropriations bill, trucking interests and safety groups are battling over an amendment that would suspend the current 34-hour restart provision of the hours of service rule.

American Trucking Associations and its affiliate, the Truckload Carriers Association, are challenging assertions of the safety groups that oppose the amendment.

And Transportation Secretary Anthony Foxx registered his “strong objection” to the amendment.

At issue is the provision in the 2013 hours of service rule that requires drivers to take two periods off between 1 a.m. and 5 a.m. during their 34-hour restart, and limits use of the restart to once a week.

ATA contends that the provision reduces productivity for some carriers and may increase risk by putting more trucks on the road during Monday morning rush hour.

The Federal Motor Carrier Safety Administration says the provision will improve safety because nighttime sleep is more restorative than daytime sleep.

Sen. Susan Collins, R-Maine, has championed ATA’s effort to suspend the provision and revert to the pre-2013 restart, which does not contain those restrictions.

Under her amendment to the appropriations bill, FMCSA would study the restart by comparing the work schedules and fatigue of drivers who operate under the old restart and the new one. The study also would compare five months of work schedules and safety critical events, such as crashes and near-crashes, for fleets of all sizes and types of operations.

As decision time approaches this week, safety groups have been pressing Congress to reject the amendment.

In a letter to congressional leaders, Advocates for Highway Safety and other groups described the suspension as an “assault” on truck safety that would significantly increase working hours for truck drivers.

“While the proposed change to the HOS rule has been portrayed as a ‘minor tweak’ to the rule, it is, in fact, a major change,” said Jacqueline Gillan, president of Advocates and numerous other signatories to the letter. “Working and driving hours will increase from 70 to 84 hours.”

ATA responded with a letter to the same leaders saying that the safety groups are attempting to mislead Congress.

“This language does not, as critics suggest, eliminate use of this rest provision,” said ATA President and CEO Bill Graves. “Instead, it would suspend unwarranted restrictions on the use of the provision while FMCSA conducts a mandated study of the net safety impacts of them.”

Over the weekend, the Truckload Carriers Association joined the fray with a call for a grassroots effort to support the amendment.

Meanwhile, DOT Secretary Foxx registered his strong objections to the amendment in a letter to Sen. Barbara Mikulski, D-Md., chair of the Appropriations Committee.

“The provision at issue is a central element of a comprehensive rule that ensures that truck drivers have adequate rest,” he said.

“The evidence clearly shows that truck drivers are better rested and more alert after two night of sleep than one night, and that unending 80-hour work weeks lead to driver fatigue and compromise highway safety,” he said.

FMCSA wants to keep the provision in place while it conducts the study that Collins called for in her amendment.

More details about the appropriations bill will come clear this week as the Thursday deadline nears.