Truck driver hours of service took center stage Tuesday as Senators grilled Anne Ferro, chief of the Federal Motor Carrier Safety Administration, on the new 34-hour restart provision.

The exchanges during a Senate Commerce Committee hearing on the federal highway program were a prelude to a showdown Thursday on the restart.

Trucking and shipping interests led by American Trucking Associations are lobbying Senate appropriators to suspend the new restart for a year while the Federal Motor Carrier Safety Administration studies the impact of the provision.

The new restart, which took effect in 2013, requires two periods off between 1 a.m. and 5 a.m. and limits use of the restart to once a week. The old one does not contain these restrictions.

ATA evidently has changed part of its position on the matter. Previously, it was asking appropriators to cut off funding for enforcement of the provision while the Government Accountability Office finishes a study of the issue.

With its call for FMCSA to study the issue, ATA is adopting a portion of the approach suggested by a coalition of trucking companies, safety advocates and the Teamsters union.

The coalition proposed having the agency accelerate the electronic logging mandate and use data from the logs to study the effect of the restart. The study would compare drivers who use the new restart to drivers who use the old one.

The difference is, ATA wants the provision suspended but the coalition wants to keep the provision in place while the study is under way.

The coalition, led by The Trucking Alliance whose members include Maverick USA and J.B. Hunt, contend that the provision is not perfect but should be tested using objective data from driver logs.

Lane Kidd, managing director of the Alliance, said the coalition’s plan calls for FMCSA to accelerate work on the final electronic logging rule so the devices can be used in the restart study.

“We applaud ATA and the other groups for supporting this plan, because the electronic logging device mandate will come out almost a year before anyone expected and those devices will give us the data to settle this whole hours of service debate forever,” Kidd said.

“We do not feel that it would be sound policy to defund parts of the hours of service rule because it will compromise our law enforcement community and it will give carriers that use paper log books a distinct advantage over carriers that have already installed electronic logging devices,” he said.

In a statement ATA did not directly address the apparent change in its position. It said the new restart has harmed the industry and drivers and done little to improve safety.

“ATA supports any and all efforts to reverse the unjustified and unsupported changes,” said spokesman Sean McNally.

ATA spelled out its new approach in a June 3 letter to top Senate appropriators, arguing that the provision creates operational inefficiencies, cuts driver pay and does not improve safety.

"The purpose of this letter is to communicate our support for both the proposed Commercial Motor Vehicle Driver Restart Study and a one-year suspension (of the new restart restrictions)," ATA wrote.

"The proposed CMV Driver Restart Study is a clear acknowledgement by all who support it that the new restart restrictions lack the research basis, data and analysis necessary to justify them."

Joining ATA are numerous shipping interests, including the National Industrial Transportation League, as well as FedEx, UPS and many state trucking associations.

The Senate Appropriations Committee will consider these issues at a markup session Thursday morning. Close followers of the matter say it is not clear where the committee will come down.

The Commerce Committee hearing, held in preparation for reauthorization of the highway program, covered railroads, pipelines and federal research programs as well as trucking.

During the trucking portion, Sen. Kelly Ayotte, R-N.H., led the charge against the restart provision. Ayotte has championed ATA’s effort to suspend the provision. Last December she offered a bill to that effect, joining Rep. Richard Hanna, R-N.Y., who offered a similar bill on the House side.

“I’m shocked at how many businesses are coming up to me and telling me about the impact of this rule,” Ayotte told Ferro.

The companies say they are going to have to drive more during the day as a consequence of the two-night, 1 a.m. to 5 a.m. sleep requirement in the provision, she said.

Ayotte challenged Ferro to defend FMCSA’s recent analysis of the restart, which the agency said proves the benefit of the provision.

Noting that the study covered 12 days of data using 106 drivers, Ayotte asked if the sample was large enough to produce a valid result.

Ferro replied: “It’s the largest naturalistic study ever done in trucking, so it’s statistically very relevant.”

Under further questioning Ferro acknowledged that the provision could put more truck drivers on the road during the day, rather than at night when traffic is less dense.

Ferro said the safety impact of this is incremental and outweighed by the benefits of drivers having more nighttime sleep.

In another exchange, with Sen. Deb Fischer, R-Neb., Ferro acknowledged that the impact of the provision extends beyond the long-haul, over-the-road irregular route industry.

“We have seen that carriers that offer scheduled service that still exceed a 60-hour 7-day week are feeling the impact of the rule as well,” she said.

She told Fischer that the agency intends to analyze these questions in a naturalistic driving study using onboard technologies.