More than 70,000 bridges across America are rated structurally deficient like the span that collapsed in Minneapolis, and engineers estimate repairing them all would take at least a generation and cost more than $188 billion (€137 billion).
That works out to at least $9.4 billion (€6.9 billion) a year over 20 years, according to the American Society of Civil Engineers.
The bridges carry an average of more than 300 million vehicles a day.
It is unclear how many of the spans pose actual safety risks. Federal officials alerted the states late Thursday to immediately inspect all bridges similar to the Mississippi River span that collapsed.
There are 756 such steel-deck truss bridges, according to highway officials. No list of bridge locations was available.
In a separate cost estimate, the Federal Highway Administration has said addressing the backlog of needed bridge repairs would take at least $55 billion (€40 billion). That was five years ago, with expectations of more deficiencies to come.
It is money that Congress, the federal government and the states have so far been unable or unwilling to spend.
"We're not doing what the engineers are saying we need to be doing," said Gregory Cohen, president of the American Highway Users Alliance, an advocacy group representing a wide range of motorists.
"Unfortunately when you consistently underinvest in roads and bridges ... this is the dangerous consequence," Cohen said of Wednesday's deadly Mississippi River bridge collapse in Minneapolis. He said engineers have estimated $75 billion (€55 billion) a year is needed just to keep highways and bridges from further deterioration, but that only around $60 billion (€44 billion) a year is being provided.
At least 73,533 of 607,363 bridges in America, or about 12 percent, were classified as "structurally deficient," including some built as recently as the early 1990s, according to 2006 statistics from the Federal Highway Administration.
The federal government provides 80 percent of the money for construction, repair and maintenance of the so-called federal-aid highway system including Interstate highways and bridges. But states set priorities and handle construction and maintenance contracts.
A bridge is typically judged structurally deficient if heavy trucks are banned from it or there are other weight restrictions, if it needs immediate work to stay open or if it is closed. In any case, such a bridge is considered in need of considerable maintenance, rehabilitation or even replacement.
Congressional leaders say the number of bridges in need of repair is too high and the funding too low.
There is crumbling infrastructure all over the country, said Democratic Senate Majority Leader Harry Reid. Sen. Patty Murray, the Democrat who heads the Senate panel that controls transportation spending, said the Bush administration has threatened vetoes when Democrats try to increase such spending.
White House deputy press secretary Scott Stanzel, accusing the Democrats of using the bridge collapse for partisan purposes, said Bush had increased funding for federal highways by about 30 percent during his administration. The president had threatened to veto legislation not over highway funding but because of billions of dollars in excess funding in other areas, Stanzel said.
Democrats were not alone in calling for more bridge funding, the AP reports.
Mike McGray, owner of Progressive Contracting Co., said he had "no idea" what may have caused the bridge to give way. One of his workers was missing and presumed dead.
San Francisco-based engineering and construction company URS Corp. said it had issued a draft report in 2006 that recommended the bridge be retrofitted "to eliminate the possibility of member fracture."
Investigators planned to rebuild the bridge piece by piece off-site to figure out what had happened, National Transportation Safety Board Chairman Mark Rosenker said.
City officials said the search and subsequent clean-up would take at least several days. Searchers used sonar and engineers lowered the river level to aid the effort, Reuters reports.
Prepared by Alexander Timoshik