Imagine the new slogan on license plates: "Pennsylvania, Land of Tolls."

The state legislature is increasingly enchanted by the notion of converting free interstates into toll roads as a way to raise money for highway maintenance and mass transit operations.

When the state House reconvenes Monday to tackle transportation funding, there are likely to be new calls for new toll roads. I-80 across northern Pennsylvania. I-81 in eastern Pennsylvania. I-79 in western Pennsylvania. Even Philadelphia's two main interstates, the Schuylkill Expressway (I-76) and I-95.

But there are serious federal barriers to widespread tolling on existing interstates that could burst the bubble in Harrisburg.