Partisan differences halted Senate debate on an appropriations bill that includes a suspension of the 34-hour restart provision of the hours of service rule.

As the debate began, Sen. Cory Booker, D-N.J., introduced an amendment that would change Sen. Susan Collins’s provision calling for suspension of the restart and a study of its impact.

At issue is the provision in the 2013 HOS 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.

Collins wants to suspend that provision and revert to the pre-2013 restart, which does not contain those restrictions.

During the suspension, the Federal Motor Carrier Safety Administration would study the restart by comparing the work schedules and fatigue of drivers who operate under the old restart and the new one.

Booker’s amendment would keep the study but not suspend the current restart.

“We believe it is absolutely unacceptable to suspend the rule while the study is under way,” Booker said.

Before the matter could be brought to a vote, though, Majority Leader Harry Reid, D-Nev., and Republican Leader Mitch McConnell, R-Ky., disagreed over procedural issues and Reid pulled the bill from the floor.

It is not clear when debate might resume. Whatever the outcome in the Senate, the outlook for suspension is not clear.

The House appropriations bill does not contain a suspension provision, and the two chambers will have to agree on a final policy before the matter is settled.

If they cannot agree on an appropriations measure, the fallback will be a resolution to continue transportation funding – and the restart provision – as they currently stand.