The nation's roads and bridges need intensive care.

One in three major U.S. roads is in poor or mediocre condition, and one in four bridges is either functionally obsolete or structurally deficient, according to the American Society of Civil Engineers.

That disrepair costs motorists in broken vehicles and drives up the expense of freight, which increases the cost of doing business. That's a drag on economic growth and the nation's international competitiveness.

Unfortunately, the federal funding mechanism that pays for much of the roadwork also needs work. The Federal Highway Trust Fund is on the brink of bankruptcy. The revenue sources that sustain it no longer generate enough money to cover the maintenance that has already been authorized, much less all the work that actually needs to be done.

To feed the fund, Washington relies on the gasoline tax of 18.4 cents a gallon and 24.4 cents per gallon of diesel fuel, and a small tax on truck sales and truck tires. That raises 85 percent of the federal dollars devoted to roads, bridges and rail. In recent years, Congress has added a few billion dollars from general tax revenue.

Despite its critical function in keeping the roads in good repair, the gas tax has been unpopular since its inception in 1932 at a penny a gallon. Although Republican Ronald Reagan and Democrat Bill Clinton each signed big bumps in the tax, it is projected to raise just $39 billion next year. That's short of the $53 billion in planned spending and a long way from the $170 billion a year the Federal Highway Administration says it would take to significantly improve the condition of federal highways and bridges.

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Fuel taxes were last increased in 1993. Over that time, the miles vehicles travel per gallon has increased, resulting in more road wear and tear per gallon. And inflation has eroded the money's purchasing power. If the tax had been adjusted with the cost of living, today it would be 29 cents a gallon on gasoline and 39 cents a gallon on diesel, according to the Congressional Budget Office.

The Surface Transportation Act, which sets federal highway funding, expires Oct. 1. So it will soon be crunchtime for Congress to reach a deal. Doing too little to reverse the slow rot would be irresponsible. It would also squander an important opportunity to create jobs.

There is no agreement on where the money should come from, but a number of possibilities have been floated.

Congress could raise the taxes on gas and diesel fuel. Each additional penny per gallon would raise $1.5 billion a year. But to cover the obligations projected for the trust fund solely by raising the tax would require a 10-cent increase, according to the Congressional Budge Office. That kind of hike in gasoline prices won't go down easy in Congress or with the public.

President Barack Obama proposed another option in his dead-on-arrival 2015 budget. He would devote $302 billion over four years to surface-transportation improvements. The additional money would come from overhauling the corporate tax code. Unfortunately, federal tax reform won't happen anytime soon. It would mean closing loopholes while slashing rates, and that would take more bipartisan cooperation than Congress is likely to muster in an election year.

Rep. Steve Israel (D-Huntington) is quietly shopping a proposal to tap $2 trillion in assets that corporations have parked overseas. He wants Congress to allow corporations to bring that money home at a greatly reduced income tax rate of 5.25 percent -- if they use an additional 9.75 percent to buy bonds to fund infrastructure projects. The deal should be permanent tax policy, rather than a one-time amnesty, to create a new revenue stream for infrastructure, Israel said.

There are even whispers about lifting the ban on new tolls on interstates. That's not going to happen. The ban's been in place since 1956, when the U.S. highway system was created under President Dwight D. Eisenhower. The only exceptions are state highways that had tolls before they were absorbed into the national system, and a few unpopular pilot projects.

Congress has to find the money to rehabilitate roads and bridges. It can't keep dithering while the country's underpinnings crumble.