A truck is removed from the wreckage of an Interstate 5 bridge over the Skagit River in Mount Vernon, Wash., on May 27, 2013, after the bridge collapsed May 23. (Washington Department of Transportation via AP)

When big bridges collapse they make news, but it generally escapes notice when decrepit bridges just cause prices to go up on almost anything that gets to the store by truck.

The sorry condition of U.S. bridges warrants a headline this week because a leading think tank that focuses on the nation’s deteriorating infrastructure says 66,405 of them are structurally deficient.

The good news is that the overall number of bad bridges has declined, and that a structurally deficient rating doesn’t mean a bridge is about to collapse.

But what it does mean, in many cases, is that a bridge has weakened to the point where it can no longer handle the heavy loads it once did. When lower weight restrictions are imposed, the big trucks that deliver goods of all sorts have to detour, making their routes longer, and that cost generally trickles down to the price consumers pay for almost everything.

“That has an impact on the economy,” said David Goldberg, communications director for Transportation for America. “It would add to the cost of transporting goods if a truck can’t take a direct route. That also means you see big trucks in places you don’t expect to see them, and a lot of people are nervous about big trucks and prefer that they stay on the biggest roads.”

At the beginning of this year, federal data show that reduced weight limits were imposed on 60,971 bridges. The District had three of them, 542 were in Maryland and 1,210 were in Virginia, Federal Highway Administration records show. Maryland reported that 30 bridges were closed, while Virginia shut down 40 of them. Kansas had more weight-restricted bridges than any other state, with 6,853.

The latest data on bad bridges have been tallied by Goldberg’s nonprofit group, a diverse coalition of elected officials and advocacy groups devoted to transportation issues.

The group put out a report Wednesday that uses state and federal statistics to put a fresh face on an existing issue, and to raise a question rarely heard above a whisper in Washington because Capitol Hill hasn’t come up with a good answer to it: Where will the $76 billion come from that the Federal Highway Administration says is needed to repair deficient bridges that carry 260 million vehicles each day?

Phillip R. Herr, who leads the infrastructure division in the Government Accountability Office, described the dilemma in testimony to a House committee last week.

“Calls for increased investments come at a time when traditional transportation funding sources are eroding,” Herr testified. “Funding is further complicated by the federal government’s financial condition and fiscal outlook.”

With nearly half of the deficient bridges at least 65 years old, Transportation for America points out that “the maintenance backlog will only deteriorate as bridges age and costs rise.”

Meanwhile, the report says Congress gambled in the latest transportation bill by eliminating targeted funding for bridge repair, allowing states to spend transportation money as they like so long as they meet new performance standards. The report says that those standards have not been set, and that even when they are, the law limits federal officials’ ability to enforce them.

“There are a lot more projects competing for what would have been bridge money in the past,” Goldberg said. “And states are going into their sixth or seventh year of budget troubles, what with the economy.”

The transportation group credits the economic stimulus with accelerating the rate at which states repaired bridge deficiencies, reducing their number by more than 11,000 since 2004.

“The danger now is complacency,” Goldberg said. “The tricky thing for the future is that the funds are in question.”

Three bridge collapses that are among the most notorious in recent U.S. history were not caused by structural deficiencies.

A 1989 earthquake centered in Loma Prieta caused the upper deck of the San Francisco-Oakland Bay Bridge to collapse onto the lower deck, killing a driver.

Though an eight-lane bridge in Minneapolis was listed as deficient, the National Transportation Safety Board concluded that the bridge, which collapsed in 2007, killing 13 and injuring 145, had been flawed from its construction in the 1960s. Gusset plates used to join its steel beams weren’t strong enough to bear the weight. That was exacerbated later when two inches of concrete added to the road surface increased the bridge’s weight by 20 percent.

A Washington State bridge over the Skagit River collapsed when an overly tall tractor-trailer clipped an overhead support beam, causing a collapse that sent two vehicles tumbling 50 feet into the water below. Though that bridge, built in 1955, was considered obsolete — in part because it lacked sufficient clearance for tall trucks — it was not listed as structurally deficient.