HAGERSTOWN, Md. (AP) — Safety advocates say they fear a Republican provision added to a must-pass spending bill this week may be just the beginning of a rollback of transportation safety rules.

The provision effectively blocks Obama administration safety rules aimed at keeping tired truckers off the road.

The American Trucking Association says next month, when both the White House and Congress will be under Republican control, it will seek to block state laws that require additional rest breaks for truckers beyond what is required by federal rules. The association says there should be one uniform national rule on work hours for interstate truckers.

Jim Hall, the National Transportation Safety Board chairman during the Clinton administration, says that with no Democratic president to check Congress, “it’s going to be an open season on safety.”