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When it comes to America's dilapidated infrastructure, political spectacle is taking precedence over common sense, and drivers and businesses are suffering.

Politicians are pushing to use scarce public funds to build new bridges, experts say, instead of spending that money on repairing and maintaining existing structures.

"It's a lot harder to cut a ribbon on a pothole repair project," said Roger Millar, a vice president at Smart Growth America, an advocacy group that focuses on sustainable development.

America's bridges, once a symbol of the nation's engineering and construction prowess, are crumbling. Every day, millions of Americans drive over thousands of bridges that the government says are in lousy shape. In recent years, two have already collapsed, causing deaths, slowing transport and harming local businesses.

Despite the recent infusion of $26 billion in federal "stimulus" spending, the problem is expected to worsen as tens of thousands of bridges built nearly 50 years ago for the national Interstate highway system reach the end of their useful life.



"When you look at how big the backlog is and how big that spending gap is, the entire stimulus package was less than what it would require to fill a single year's funding gap for just maintenance," said Jaime Rall, transportation senior policy specialist at the National Conference of State Legislatures.

Shortchanging maintenance and replacement can bring an even higher economic and human toll. That reality was brought into sharper focus following the 2007 collapse of the I-35 Mississippi River bridge in Minneapolis that killed 13 people and injured 145. The failure of the eight-lane, 1960s-era steel truss arch bridge was blamed on a design flaw that meant that a failure of a single structural element would bring down the entire bridge.

Some 18,000 other U.S. bridges share a similar "fracture critical" design, including the 1950s-vintage I-5 Skagit River bridge in Washington state that that collapsed in May after a truss was hit by an over-height truck. Though the truck and two other vehicles with three people fell into the river, there were no fatalities.

Every day, more than 200 million cars, trucks and buses cross a deficient bridge, according to the American Society of Civil Engineers.

Some states may be making the problem even worse by diverting scarce funds to build new bridges and roadways before replacing or repairing those that have outlived their useful lives, according to a spending analysis by Smart Growth America.

The range of spending choices can be seen in ways that states managed the one-time shot in the arm from the 2009 federal stimulus package that helped states pay for tens of billions of dollars of "shovel ready" infrastructure projects.

Of the $26 billion in transportation-related funds, a third went to building new roads and bridges, according to Smart Growth America's analysis. Eleven states spent more than half of their stimulus allocation on new capacity. In five of those states—Virginia, Louisiana, Texas, Hawaii and Arkansas—more than half of their existing highway infrastructure needs repair.

"You can look at a state like Arkansas that spent its money on system expansion while at the same what they had was falling apart," said Millar. "Not the smartest expenditure of dollars."

But economic growth and development continue to strain existing capacity and create demand expanding the network of roads and bridges that feed that growth.

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In northwest Arkansas, for example, continued growth and hiring by large employers like Wal-Mart, Tyson Foods and truck carrier J.B. Hunt has helped keep the jobless rate well below the national average.

"During the recession, that part of the state continued to grow and prosper, and that's where we're seeing some tremendous capacity issues on our road program," said Randy Ort, a spokesman for the Arkansas state Highway and Transportation Department.

That growth brought increased population growth and higher volumes of freight shipments. Maintaining that growth meant extending and widening Interstate 540 and replacing bridges and overpasses, some of which weren't deficient.

That kind of new construction further raises costs in two ways, said Millar. First, it creates that many more miles of highway and bridge to maintain.

"Adding capacity to solve a congestion problem is like buying a bigger pair of pants to solve a weight problem," said Millar. "You're not solving the problem you're accommodating the problem."

Building new roads and bridges also diverts money from relatively cheap maintenance projects, which further raises the longer term cost of repair or replacement.

A worker looks at the collapsed portion of the Interstate 5 bridge at the Skagit River Friday, May 24, 2013, in Mount Vernon, Wash. Elaine Thompson / AP

"It's a significantly better investment to spend money on a bridge that's in good condition now than to have to repair it when it becomes structurally deficient," said Steve Davis, a spokesman for Transportation for America, a coalition of transportation and land use policy groups. "It's sort of like staying ahead of things with your car. You're better off keeping up with oil changes than waiting until your engine seizes up."

The dearth of funding to fix the problem makes the choices that much harder for transportation officials. The recent stimulus highway spending was a drop in the bucket compared to the total annual highway spending of about $160 billion a year, about a quarter of which comes from the federal government.

But because federal officials don't track how much money state and local governments devote to bridge repair and replacement, it's hard to know how well the money is being spent, according to a report last month by the Government Accountability Office.

"(The) lack of comprehensive information on state and local spending makes it impossible to determine the impact of the federal investment on bridges," the report concluded.

The scope of the problem, however, is not hard to measure. Of the more than 600,000 bridges monitored by the Transportation Department, more than a quarter were built in the 15 years following the establishment of the Interstate Highway system in 1956. Every year, roughly 10,000 of those bridges reach the end of their 50-year lifespan.

As the need for repair and replacement widens, though, available funding is getting squeezed.

Just to keep the system from further falling apart would require another $14 billion in federal spending per year, according to a recent CBO report. Needed improvements would cost another $50 billion, the CBO said.

But even without additional spending, the Highway Trust Fund is expected to go broke by 2015, in part because the federal 18.4-cent a gallon gasoline tax hasn't been raised in 20 years. Gasoline taxes make up about 92 percent of federal highway funding and about 40 percent of state funding. But state gas tax rates vary widely – from just eight cents a gallon in Alaska to 50.6 cents in New York.

Even as the federal gas tax has remained flat, revenues have been shrinking because overall gasoline consumption has been falling since 2007. As the average mileage of the cars and trucks on the road continues to rise, those gas tax receipts will continue to fall.

To cover projected federal highway spending, CBO estimates the gas tax would have to be raised by 10 cents a gallon. That's not a campaign promise likely to win support from many voters.

Since 2008, Congress has kept the trust fund afloat by tapping $41 billion in other taxes; another $12.6 billion has been authorized for 2014. Given the ongoing federal budget squeeze, those transfers aren't sustainable, CBO said.

State funding for bridge repair and replacement is also coming up short.

Since the Great Recession shrank income and property taxes, states have been scrambling to balance the books at a time when few voters are in the mood for tax increases. That's left many transportation departments fending off efforts to tap their revenues to fund a variety of non-transportation needs.

"Instead of trying to raise the taxes they're just trying to protect the money that's already there," said Rall.

—By CNBC's John W. Schoen. Follow him on Twitter @johnwschoen.

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