When the House finally approved a transportation-funding measure , you could almost hear Gold Dome denizens exhale. It was the 27th day of the session, and most any conversation about any topic had included at least the question of whether it could be tied somehow to the $1 billion gorilla in the building.

But it didn't take long for everyone to inhale again. For the next question was what would come of House Bill 170 in a more skeptical Senate.

We should get an idea this week of how senators intend to change the bill. In the middle of that debate will be Tommie Williams, who chairs the Senate Transportation Committee.

There are two things to keep in mind here about Williams, who represents Vidalia onion country. He spent two years atop the Senate as president pro tempore, so he knows what it takes to round up a GOP majority. And he runs a business that fills 12 trucks with diesel fuel every day, so he knows about the need for good roads and the burden of fuel taxes.

“Most senators believe that we should have some skin in the game,” Williams told me after the Senate adjourned Wednesday, “that we shouldn’t just look for a tax increase without looking at our own budget.”

That means shifting more than just the “fourth penny” of the motor-fuel tax from the state’s general fund to the transportation budget, as HB 170 does.

“The motor fuel tax is a diminishing tax” thanks to fuel-efficiency gains, he said, “so we’re trying to find something that’s a growing number.”

One number that’s been growing in recent years is the state’s general revenue. “If we were to put a couple hundred million dollars a year” from general revenue growth into transportation, he said, “within a few years you could generate some significant money.”

He conceded that requires “the will of the Legislature” for years to come, whereas an excise tax on gasoline is constitutionally bound to go to DOT. “Unless you pass a constitutional amendment, you can’t guarantee that happens. But I think we need to culture ourselves to believe if we have excess revenue, it’s not just education and bonds we look at. We need to look at transportation.”

One place he doesn’t think senators will look for money is from local governments. Currently, HB 170 shifts some local sales taxes on gasoline into a statewide excise tax, and raises the rate on everything else covered by local sales taxes by 25 percent -- creating a net double-digit increase in local sales tax revenues in the aggregate. (SPLOST and E-SPLOST monies are not shifted due to constitutional considerations, although the bill would restrict how they are spent.)

“We’re not taking any locals’ money,” Williams said. “I have not talked to a senator who thinks we should be taking the locals’ money. … You can’t tell a county that’s got 40 percent of their money coming in (from) motor fuel that they’ve got to spend it all on transportation. It just doesn’t work for them.”

Oh, there is a third thing you should know about Williams as it relates to this conversation. Though he lives in South Georgia, his parents grew up in Atlanta. Their first date included a ride on the city’s old streetcar lines.

A self-proclaimed “big fan of the Beltline,” Williams echoed statements by House leaders about paying attention to the way businesses have warmed to the idea of rail.

“When companies want to locate next to the MARTA station,” he said, “somebody needs to wake up and say we need to think about transit.”