WASHINGTON – Oil-rich Texas has built more highways and bridges than any other state, but over the next two decades it will fall $170 billion short of what it needs to keep the sprawling network in good repair.

In California, transportation officials estimate that 60 percent of the state’s roads and a quarter of its bridges need to be repaired or replaced, at a projected cost of $70 billion over a decade, some $52 billion more than the available funds.

North Carolina anticipates that it will fall short of keeping its highways in current condition by $22 billion over the next 30 years, and would need more than twice that amount to improve them.

America’s highway system, once a symbol of freedom and mobility envied the world over, is crumbling physically and financially, the potentially disastrous consequence of a politically driven road-building binge.

President Obama, state transportation officials, civil engineers, road builders and business groups all say that the country needs to invest trillions of dollars in its infrastructure, yet there’s little consensus on how to finance it or what the most pressing needs are.

The Congressional Budget Office estimates that the country needs $14 billion in additional federal funds each year just to maintain highways and $50 billion more to improve them.

There’s no single cause of the financial squeeze, and federal data reveal only part of it. Some states have raised their own gasoline taxes to pay for highway construction and maintenance and to depend less on federal funding. Others haven’t changed their gas taxes in years and rely on federal money to make up for it.

But federal government analysts, taxpayer advocates and transportation experts have warned for at least a decade that many states were spending too much on building highways and too little on fixing them, and that their maintenance costs would skyrocket if they didn’t change course.

“We’ve engaged in a dangerous game of deferred maintenance,” said Brian Taylor, a professor of urban planning and the director of the Institute of Transportation Studies at the University of California, Los Angeles.

Five years after an interstate highway bridge collapsed in Minnesota, killing 13 people and injuring 145, the country still has a bridge repair backlog of $65 billion, according to the Federal Highway Administration.

At a time when Congress is proposing significant budget cuts and tax increases have little support, states are canceling or scaling back highway projects. They’re looking for private partners to help finance construction, and still coming up short. Motorists are discovering that the roads they thought were free are anything but.

Over the past four months, McClatchy Newspapers traced the extent and causes of yet another financial crisis that’s developed below the radar of most Americans.

A review of government reports, an analysis of thousands of state and federal campaign donations, and interviews with dozens of current and former elected officials, watchdogs and transportation officials showed that there were a lot of hands on the wheel as the system veered off course.

For example:

The oldest parts of the interstate highway system have reached the end of their life cycle, including thousands of bridges dating to the 1960s, a potential threat to public safety and commerce demonstrated by the Minnesota bridge collapse.

The federal gasoline tax no longer covers the country’s annual highway spending, but few leaders in Washington are willing to take on the political risk of increasing it, which forces states to borrow more money, raise tolls or ask their residents to approve new taxes.

Despite a ban on members of Congress “earmarking,” or skimming money for pet projects back home, lawmakers and the special interests that bankroll their campaigns still exert outsized influence on where federal highway funding goes.

The Department of Transportation long ago ceded control over most highway decision-making to the states without well-defined national transportation goals, leaving a large portion of federal money up for grabs for those with the most clout.

Like the Roman Empire, “civilizations fall because they don’t maintain their infrastructure,” said David Burwell, the director of the climate and energy program at the Carnegie Endowment for International Peace in Washington.

“Everybody likes to build things, but nobody likes to maintain them,” he said. “We paid for them once. Why should we pay for them again?”

When Al Biehler became Pennsylvania’s transportation secretary a decade ago, he found that the state had been spending more on expanding its highway system than it had on keeping it in good repair.

“If you don’t put money into fixing things,” Biehler said, “there will be more things to fix.”

So he did the unthinkable: He put the brakes on some projects, risking the wrath of highway contractors and the state lawmakers who supported them.

“Projects that we knocked off the program, some of them weren’t terrible projects,” he said. “I just felt we couldn’t afford them.”

According to the National Center for Pavement Preservation, a research lab for road-building materials at the Michigan State University engineering school, every dollar spent to maintain a road in the first 15 years of its life saves $6 to $14 in maintenance costs after 20 years.

The Federal Highway Administration doesn’t require states to put money into repairing roads before building new ones.

Pennsylvania was spending about as much of its federal funding on expansion as it was on maintenance in 2004, according to federal data reviewed by McClatchy. By 2011, the state was spending about four times as much on repairs, and it was still struggling to keep up.

The Pennsylvania State Transportation Advisory Committee reported in 2010 that the state needed an additional $2.1 billion a year to properly maintain its highways and bridges.

“More than half of our bridges have reached their intended life-span date,” said Barry LePatner, a New York construction lawyer who’s cataloged nearly 8,000 of the nation’s most troublesome spans. “Without maintenance money, cost of repair equals cost of replacement after a certain period of time.”

Some budget watchdogs were encouraged that the most recent federal transportation bill, MAP-21, which Congress approved last summer, pushes states to develop performance standards for federal highway spending that result in the greatest improvement to roads and bridges.

But it’s too soon to know whether the measures will have any impact, and the legislation expires at the end of next year. Meanwhile, states face tough choices. Emil Frankel, who was assistant secretary for transportation policy under President George W. Bush and is a former Connecticut transportation commissioner, said the country needed to establish priorities.

“Thirty years ago, ‘like it’ might have been good enough,” said Frankel, who’s now a visiting scholar at the Bipartisan Policy Center, a research center in Washington. ” ‘We’ll do it because we like it.’ We can’t afford to do that anymore.”

It’s been 20 years since Congress raised the gasoline tax. The 18.4-cents-a-gallon tax has lost a third of its buying power to inflation and rising construction costs.

The tax feeds the federal Highway Trust Fund, which long has paid for part of highway building and repairs in all 50 states.

The fund used to carry a surplus, but lawmakers have bailed it out since 2008 by tapping the Treasury for $50 billion.