A Senate Democratic aide told The Hill that about 10 amendments will be voted on Thursday, with the remaining votes expected to come next Tuesday.
The amendments to be considered include a measure from Sen. John HoevenJohn HoevenGOP senators unveil bill to give Congress control of consumer bureau budget Dem senator: DeVos bigger threat to education than grizzlies Senate set for high-noon vote to confirm DeVos MORE (R-N.D.) that would authorize the Keystone XL pipeline without President Obama's approval, and one from Sen. Ron WydenRon WydenTech, advocacy groups slam DHS call to demand foreign travelers' passwords Dem bill would force Border Patrol agents to get warrants before searching devices Senate Dems move to nix Trump's deportation order MORE (D-Ore.) that would block exporting oil brought into the country through the controversial pipeline.
Also to be considered is an amendment from Sen. David VitterDavid VitterMercury brings on former Sen. Vitter, two others Lobbying World Bottom Line MORE (R-La.) to extend oil and gas drilling permits in the Outer Continental Shelf, and one from Sen. Bob CorkerBob CorkerRepublicans play clean up on Trump's foreign policy GOP Congress unnerved by Trump bumps Trump makes nuclear mistake on arms control treaty with Russia MORE (R-Tenn.) to reduce the 2013 discretionary spending cap.
Several of the measures will require 60 votes to be approved.
Democrats have framed relenting on amendments as the only way to move forward in the Senate on the transportation bill, which even Republican leaders in the House have publicly acknowledged could end up forming the basis of a final authorization measure that becomes law.
"I was hoping we wouldn't have to face convoluted amendments that are completely non-germane amendments, but they are insisting on them, so we'll have to deal with those," Sen. Barbara BoxerBarbara BoxerCarly Fiorina 'certainly looking at' Virginia Senate run Top Obama adviser signs with Hollywood talent agency: report Democrats vie for chance to take on Trump as California governor MORE, the chairwoman of the Senate Environment and Public Works Committee, who has shepherded the transportation bill to the Senate floor, said in a press conference Wednesday.
"It probably would be rolling back Clean Air Act rules," Boxer said of the amendments to the highway bill. "I can't imagine why anyone would want to do that, but there are some that want to do that."
The Senate began consideration of the highway bill amendments at 9:30 Thursday morning. The chamber is expected to resume debating the measure at about 10:45.
— Pete Kasperowicz contributed to this report.