ANNAPOLIS -- A Maryland Senate committee passed legislation that would raise the tax on gasoline for the state's roads and transit projects.

The panel voted 9-4 to send the bill to the full Senate, where it could be passed next week.

Before the vote, the Senate Budget and Taxation Committee killed a number of amendments that would have required the funds raised from the taxes to go to state highways instead of mass transit.

Sen. Richard Colburn, R-Eastern Shore, offered two amendments that would require some or all of the new revenue to go to the state's roads and bridges, arguing that motorists who use that infrastructure are the ones paying the new tax.

Colburn was joined in support by Sen. Richard Brinkley, R-Frederick and Carroll counties.

"If you're going to let this issue move forward, at the very least let the motoring public benefit from it," Brinkley said.

The amendments were killed by the Democratic majority on the committee.

The tax increase would raise an estimated $4.3 billion in badly needed funding for transportation projects over the next six years. The state's Transportation Trust Fund has enough cash only to maintain current infrastructure and is slated to go bankrupt by 2018.

The bill would apply a 1 percent wholesale tax on gasoline starting July 1, meaning an increase of about 4 cents per gallon at the pump. The bill would ratchet that tax up to 3 percent by July 1, 2015.

The measure also would index Maryland's flat 23.5-cents-per-gallon gas tax to inflation but caps any increases at 8 percent to protect against years with wild inflation.

Colburn also offered a failed amendment to remove the indexing provision of the bill, claiming it was a lazy way to avoid having to come back and address the measure in the future.

Maryland's gas tax has remained at its current rate since 1992.

The committee also approved a constitutional amendment that would put a lockbox on the Transportation Trust Fund. The governor would have to declare a fiscal emergency, and a three-fifths supermajority of both legislative chambers would have to sign off for the money to be used for anything but transportation.