The catastrophic bridge collapse in Minneapolis has focused attention on America's huge backlog of crumbling structures waiting their turn for repair. But if there isn't enough money now to fix the country's aging road system, just wait until next year.

Sometime after October 2008, the main money source for interstate repairs, the federal Highway Trust Fund, is expected to start running a deficit. When that happens, some green-lighted reconstruction projects could have trouble getting the U.S. government to pay up, forcing states to put off essential road repairs.

The impending crisis at the Highway Trust, which is supported by an 18.4-cent-a-gallon gas tax, superficially resembles the problems facing the Social Security Trust Fund. But while the retirement crisis is still years from reaching its denouement, "the highway shortfall will be upon us very soon," said Jim Berard, the communications director for the U.S. House Transportation Committee.

"This time, it's serious," he added.

No one can say precisely what will happen when the highway fund goes into the red. Money from fuel taxes will continue to pour into the trust, a sacred federal institution created along with the interstate system in 1956.

It's just that those future tax revenues won't be sufficient to meet all the federal commitments. And the current commitments are well below what is needed to keep the country's crumbling roads and bridges from shedding hunks of concrete and bits of steel. State transportation officials fear that the uncertainty could tie up road projects for years to come.

"If states don't know how much money to expect," Berard said, "they can't plan their projects. They can't prepare designs. They can't advertise for bids. Meanwhile, contractors don't know if work is coming, so they can't hire people and they can't buy equipment."

Donald S. Shanis, the deputy director at the Delaware Valley Regional Planning Commission, suggests that America is entering a period of regular infrastructure failures that will also involve railroads and water and sewer systems. A little more than two weeks ago, an aging steam pipe exploded on a crowded street in midtown Manhattan.

"We will see more and more problems with our infrastructure," Shanis predicted. "It's way too expensive to fix it all. So infrastructure will continue to fail, and not just highways."

$8 billion needed

In Pennsylvania, where an estimated $8 billion is needed to fix just those bridges that have been deemed structurally deficient, officials are pushing hard now to start construction on key projects - such as the South Street Bridge and I-95's Girard Avenue access ramps - so that federal dollars will start flowing to the state before the Highway Trust runs short of cash, Department of Transportation Deputy Secretary Rina Cutler said in an interview this spring.

But she's worried about the projects that won't get cleared for liftoff before the deficit hits. Pennsylvania has among the highest number of structurally deficient bridges in the country, according to PennDot spokesman Rich Kirkpatrick.

"Portions of I-95 are in serious condition," Cutler added. "Last Thanksgiving, a portion of the bridge deck collapsed in Philadelphia. We had to take out a lane on a holiday weekend. That part of I-95 is old and deteriorating."

Many hope Congress will find a way out of the funding morass before the Highway Trust's projected deficits start mounting, sometime in fiscal 2009, which begins Oct. 1, 2008. The simplest solution would be to raise the fuel tax, which has remained 18.4 cents a gallon since 1993, by about 5 cents.

But with a gallon of gas costing about $3, politicians may be reluctant to burden consumers with higher taxes. President Bush has repeatedly resisted plans to increase the fuel tax, Berard noted.

Unintended consequence

Oddly enough, the push to reduce American's oil consumption is partly to blame for the threat facing the Highway Trust. As motor vehicles have become more fuel efficient, gas tax revenues have slowed below projections. The high cost of gas also means that motorists are driving less. Some experts say the gas tax should be tied to the pump price, rather than fixed on each gallon consumed.

But the problem isn't only a shortfall in tax revenues. Now that the interstate system is entering its senior years, the aging network requires more and more attention. The bulk of the national road system was constructed in the 1950s and 1960s. Many sections are nearing the end of their functional life.

Meanwhile, the cost of doing road projects is rising at a record clip. As the economies of China and India rev up, those nations are investing heavily in their own road networks. Their insatiable demand for concrete and asphalt has caused material prices to rise almost 36 percent in the last two years, Kirkpatrick said.

Take the I-95 bridge over the Potomac, said Jack Basso, an executive with the American Association of State Highway and Transportation Officials. Built in 1960 for $40 million, he said, the bridge is beyond repair. It's also inadequate for today's Washington. A replacement is planned - at a cost of $2.3 billion.

Ultimately, transportation experts expect that states will have to look to new sources for funding road repairs, such as congestion taxes, new road tolls and privatization of highways.

Just last month, Gov. Rendell announced a plan to put tolls on I-80 to raise money for road projects and mass transit. But hours after the details became public, two U.S. representatives from Western Pennsylvania introduced an amendment in Washington to derail the fund-raising plan.

Some transportation experts believe that the shocking images of the Minneapolis bridge wreckage may make the public more willing to accept the costs of road repairs.

"Maybe the country will look at what happened in Minneapolis and say, 'Yes, we do need to spend more on roads,' " said Bob Borski, a former U.S. representative from Philadelphia who is now a transportation lobbyist for Pennsylvania. "I contend that, as a nation, we do not spend enough on infrastructure."

If the scenes along the Mississippi don't persuade taxpayers to spend more on road repairs and mass transit, perhaps increased congestion will.

As more roads and bridges are taken out of commission, either for repairs or because they are unsafe, motorists should expect delays.

Increasingly, states may also have to dig into their own pockets to cover the rebuilding. That may mean forgoing construction of pet civic projects, perhaps such as Minneapolis' new ballpark, located just eight blocks from the city's overstressed highway bridge.

Contact architecture critic Inga Saffron at 215-854-2213 or isaffron@phillynews.com.