In 2009, the state completed the reconstruction of a 17-mile stretch of Interstate 295 between Topsham and Gardiner. In all, 34 miles of fresh asphalt were put down over a rebuilt roadway, at a cost of $35.3 million, paid for with federal stimulus funds.

“Certainly this reflects well on Maine,” said David Cole, the commissioner of the Department of Transportation at the time. “It’s good for another 20 years.”

But what happens then?

That’s a question confronting transportation officials around the country. Much of the nation’s 46,000-mile Interstate Highway System is at or past its 50-year design life and in need of maintenance. Many areas served by the interstate system have stifling traffic congestion and need additional lanes.

The funding mechanism for highway reconstruction, the gas tax, has not kept up with inflation, rising costs and the ever-improving gas mileage of newer vehicles.

As a result, the gap between what is needed to pay for construction and what is actually collected is steadily growing.

One possible solution to our traffic dilemma comes from the Reason Foundation, a libertarian think tank that earlier this month released a study in support of per-mile tolls for the interstate system.

The study found that interstate highway reconstruction and lane-widening projects estimated to cost $983 billion could be financed with a toll system averaging 3.5 cents per mile for cars and 14 cents per mile for trucks. Each state could adjust these figures to meet regional needs, and the money earned would stay where it is paid, dedicated to the roads on which the toll was collected.

Federal law prohibits tolls on existing interstates, but Congress could change that as early as 2014.

Lawmakers should listen. New tolls, albeit a tough sell politically in many states used to freeways, would fund much-needed road repairs by charging the people who actually use the roads.

The fees would be made more fair by new technology that allows charges on a per-mile basis — through the universal electronic tolling system expected to be in place by the end of 2016 — ending the need for inefficient and sometimes dangerous toll booths.

Per-mile tolls would solve a lot of problems in Maine, where a short trip near a tollbooth can cost a lot more than a long trip that avoids one. The per-mile fees also would render moot the strategy of driving around tollbooths to avoid paying. Vehicles would be tagged at all entrances and exits, not at a tollbooth.

As a way to fund road repair, tolls already are used successfully on the Maine Turnpike, whose tolls were grandfathered when the interstate system was created. The Maine Turnpike Authority completes maintenance and upgrades to its 100 miles of divided highway without taxpayer dollars.

With a change in federal law, that same formula could be used when upgrades are needed on the state-operated stretches of interstate, I-295 and I-95 north of Augusta.

That may be preferable to relying on bonds, especially when Maine’s infrastructure needs are so plenty. In 2010, the Maine DOT identified $6.3 billion in transportation infrastructure needs for the next 10 years, with only $3.2 billion available under the current funding structure, according to the Maine Better Transportation Association.

Maine, and other states in much the same predicament, are going to need a better funding mechanism. Bonding only goes so far, and it’s unlikely federal stimulus funds will be available the next time a major reconstruction is necessary.