Drivers are used to paying a price for toll roads. State lawmakers, not so much.

A debate broke out on the Senate floor Monday after several senators began to calculate the political cost of supporting permanent toll lanes in Georgia. Two massive toll projects that will cost more than a billion dollars to build are already under construction along I-75/I-575 in Cobb and Cherokee counties and along I-75 in Henry and Clayton counties.

SB 125, sponsored by State Sen. Brandon Beach, R-Alpharetta, would enable the state to continue tolling those lanes even after construction costs have been repaid. The bill passed 42-12, but the criticisms it sparked are likely to carry over to the House.

Unlike Ga. 400, which was tolled to recoup construction costs, a permanent toll has always been planned for the two new projects taking shape along I-75 and I-575. However, state law needed to be tweaked to allow it. If approved, SB 125 would enable the state to continue collecting tolls after construction costs are paid and use the additional money for road maintenance, Beach said.

State Sen. Steve Gooch, R-Dahlonega, who formerly chaired the Senate Transportation Committee, said toll lanes are one of the best options for providing congestion relief.

“We’ve got to find new ways to fund transportation,” Gooch said. “Tolling is a good way to do that.”

But some lawmakers like Sen. Renee Unterman, R-Buford, said they disliked the idea of state collecting tolls indefinitely. Others like Charlie Bethel, R-Dalton, were concerned the state might try to impose tolls on existing interstate lanes.

That occurred with the I-85 HOT lane in Gwinnett County as part of a continuing federal demonstration project.

State Road and Tollway Authority officials have tried to dispel those concerns by saying that was a special circumstance, and that federal law generally prohibits states from slapping tolls onto existing interstate lanes. However, the Senate approved an amendment that clarified language in the bill so that the state could only construct — not “acquire” — future toll lanes.

The two upcoming express toll projects are part of a new breed of so-called “managed lanes” that the state Department of Transportation and State Road and Tollway Authority are implementing. Over the next 30 years, a third of the roughly $12 billion budgeted for transportation projects in the Atlanta area will be spent on these kinds of toll lanes.

The lanes are meant to let drivers bypass traffic, for a price. The idea is that speeds in the lane are kept moving at a 45 mph-or-greater pace by raising or lowering the per-mile cost of the toll.

Unterman, who voted against the bill, was skeptical of the promised results.

“I wish it were that easy,” she said. “In Gwinnett County, we pay $10 for a one-way trip in the (I-85) HOT lane and sometimes we don’t even move.”