(CBS) – It’s costing more to repair our roads, and there’s less tax money to do it.

So, President Obama is offering one solution: turning highways into tollways.

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CBS 2’s Derrick Blakley reports.

It’s the biggest public works project in human history: the interstate highway system. It was largely paid for at the pump.

But the federal gas tax – 18.4 cents a gallon — hasn’t gone up in 20 years, even though construction costs have. That is one reason the Highway Trust Fund is going broke.

“As we increase fuel efficiency, as we move toward alternative vehicles, the number of gallons being purchased is actually going down, and that’s driving down motor fuel tax receipts,” says Ann Schneider, head of the Illinois Department of Transportation.

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Obama is proposing another solution to augment highway funds: Let the states turn freeways into tollways.

“It’s certainly something we need to be looking at, as we go forward,” Schneider says.

There’s already a proposal to turn Illinois Route 53 into a toll road between Interstate 90 and Lake Cook Road to pay for a Lake County extension.

Rolling Meadows Mayor Tom Rooney objects because three local exits are bunched so closely, it could cost 50 cents or 75 cents just to drive a half-mile.

He says current economics dictate that if any new highways are built, they’ll probably be toll roads. IDOT agrees.

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