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 HoevenDem senator to meet with Trump Overnight Energy: Dakota pipeline standoff heats up ND senators tell pipeline protesters to vacate camp MORE (R-N.D.) that would authorize the Keystone XL pipeline without President Obama's approval, and one from Sen. Ron WydenRon WydenSenate passes college anti-Semitism bill Overnight Finance: Trump takes victory lap at Carrier plant | House passes 'too big to fail' revamp | Trump econ team takes shape Senate Dems: Force Cabinet nominees to release tax returns 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 VitterPoll: Republican holds 14-point lead in Louisiana Senate runoff Louisiana dishes last serving of political gumbo Trump tweets about flag burning, setting off a battle MORE (R-La.) to extend oil and gas drilling permits in the Outer Continental Shelf, and one from Sen. Bob CorkerBob CorkerLawmakers eye early exit from Washington Trump: 'Almost all' Cabinet picks coming next week Overnight Defense: Trump reportedly picking Mattis for Defense chief 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 BoxerTrucking riders ‘in the mix’ for short-term spending bill Lawmakers praise defense bill's National Guard bonus fix Schumer’s elevation to leader spells trouble for Democrats 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.