WASHINGTON - Although tragic in its proportion and suddenness, the collapse of a 40-year-old interstate highway bridge in Minneapolis wasn’t a surprise to those who work in the engineering and public works fields.

The bridge that tumbled into the Mississippi River in the shadow of downtown Minneapolis is one of about 159,000 of the nation’s 590,750 bridges that are deficient or obsolete, according to a 2005 infrastructure report card by the American Society of Civil Engineers.

The Federal Highway Administration’s bridge inventory estimates that about 73,000 bridges are structurally deficient and that 80,000 are "functionally obsolete," meaning they are carrying more traffic than they are designed for.

The number of deficient bridges across the nation appears to be an open secret in government and public works circles.

"I think we’re going to see bridges collapse, and we do on a regular basis," said Kent Harries of the University of Pittsburgh’s School of Engineering. "We need to start assessing it. We need to find ways to address it."

In the wake of Wednesday’s bridge disaster, the U.S. Department of Transportation yesterday ordered that states inspect "steel deck truss bridges similar" to the one that collapsed in Minneapolis.

"What happened in Minnesota is simply unacceptable," said Transportation Secretary Mary Peters. "We must have a top-to-bottom review of the bridge inspection program to make sure that everything is being done to keep this kind of tragedy from occurring again." Officials said there are 756 such bridges in the United States.

Peters pledged an immediate $5 million "to help restore the traffic flow, to clear the debris, to set up detours and to begin the repair work." She also asked the DOT inspector general to examine the highway administration’s national bridge inspection program to expose any lapses.

Funding for needed bridge repairs has lagged in recent years, engineering and transportation experts said. The civil engineers’ group estimates that the United States would have to spend $9.4 billion over the next 20 years to repair all faulty bridges.

In a separate audit, the inspector general’s office of the transportation department found that more than 6,300 of the 114,000 national highway system bridges are "structurally deficient." The report defines "deficient" as "major deterioration, cracks or other deficiencies in their decks, structure or foundations."

Those figures have improved from 2000, the inspector general found, when bad bridges numbered about 6,700.

But the same report found that although bridge inspections in three states that it analyzed - Massachusetts, Texas and New York - proved adequate, inspectors made mistakes in calculating the load that 12 of the 33 bridges examined could bear.

As structural problems develop, the report said, transportation agency officials need to do a better job of limiting the weight of vehicles using decaying bridges.

That suggests that cities and states often make do with the bridges they have, putting off repairs until they are necessary. In Minnesota, state engineers had suggested that the Interstate 35W bridge that collapsed Wednesday had structural problems. But they also suggested that the problem wasn’t an immediate threat.

Harries said that bridge repairs lose out to larger-scale, high-profile engineering projects.

"They are simply not sexy," Harries said. "Honestly, you’re not going to get your name on a bridge repair."

For engineers, accurately assessing problems in bridges is a difficult task. "You can go out and cry wolf all the time," said Chris Foley, an engineering professor at Marquette University, "but if the failure doesn’t come, the engineer looks alarmist."

Bridge failures do occur, but Harries said that most are small and don’t draw national attention.

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