The Federal Highway Administration has allowed states to take advantage of a loophole in federal regulations, delaying bridge inspections to every four years instead of the two years normally required. While most states don't use this loophole, calling it unsafe, others drive a truck through it: Nationally, 30,000 bridges are listed on the delayed-inspection schedules, including 10,000 in Illinois alone and more than 3,000 on interstate highways.

Bridges in poor condition have been allowed on these delayed timetables in violation of federal guidelines. Although federal and state officials are bound by law to closely monitor the schedules, their own records show thousands of bridges on delayed-inspection schedules — despite being too decayed, too long or too heavily traveled to qualify.

"Fracture-critical" bridges like the Minneapolis bridge, which could collapse if one part fails, have remained on delayed-inspection schedules in violation of federal regulations. The records show 622 of these vulnerable bridges on four-year timetables.

Even after the deadly collapse in Minneapolis, the haphazard system of inspections continued, with federal authorities choosing not to require re-inspection of more than 18,000 fracture-critical bridges. In a survey of every state by msnbc.com, only five states and the District of Columbia said they began to recheck all their fracture-critical bridges. The rest checked only the few hundred bridges of the particular deck-truss design used in Minneapolis.

Federal agencies that own bridges have some of the worst records for on-time inspections. Nearly 3,000 bridges owned by U.S. government agencies went more than two years between checkups.

The Senate approved the funds on a 60-33 vote as the Senate began debate on a $104.6 billion measure funding transportation and housing programs for the budget year beginning Oct. 1.

"Our bridges are deteriorating far faster than we can finance their replacement," said Sen. Patty Murray, D-Wash., lead sponsor of the bridge-repair funds. "More than one in every four bridges on U.S. highways is rated as deficient."

The underlying bill faces a veto threat from President Bush, however, for exceeding his request by $4.4 billion.

"Fully 27 percent of our 600,000 bridges have aged so much that their physical condition or their ability to withstand current traffic levels is simply inadequate," Murray said. "Roughly half of these deficient bridges - or about 78,000 bridges across the nation - are structurally deficient."

More than 700 structures will be looked at after it emerged that the bridge in Minneapolis had been classified as "structurally deficient".

Divers have resumed their search for victims in the Mississippi river. At least eight people are still missing.

First Lady Laura Bush is set to visit Minneapolis and will go to the scene.

33 percent of the nation's major roads are in "poor or mediocre condition."

36 percent of major urban highways are congested.

26 percent of bridges are "structurally deficient or functionally obsolete."

Meanwhile, funding for improvements and maintenance continues to fall short. When Congress last passed a major highway funding bill in 2005, the Federal Highway Administration estimated it needed $375 billion to fund repair and improvement projects, but the final bill authorized just $286 billion.

On Thursday, Sen. Frank Lautenberg, D-N.J., a member of the Senate Commerce Committee, said that the nation's transportation infrastructure has been underfunded for years and that the Bush administration has threatened to veto proposals to increase funding.

"We want to get the bills done and want to get them increased at a sufficient amount," he said. "We spend over $3 billion a week on the war. So there is a lot of money that is being spent in other places that we have to recover and put into our highways. Because we face immediate danger in lots of places, and the public deserves better than that."

Department of Transportation (DOT) statistics show that 160,000, more than a quarter, of the nation's bridges are rated "structurally deficient" or "functionally obsolete," and many don't have proper warning signs restricting weight loads.

The 160,000 bridges rated deficient are not necessarily unsafe, according to DOT, as long as there are restrictions on the types of vehicles, weight or traffic volumes allowed on the bridge.

But a 2006 investigation by the DOT inspector general revealed that one out of every 10 "structurally deficient" highway bridges did not have load ratings that reflected the condition of the structure. In other words, posted signs told drivers the bridge could carry more than it could safely handle.

"In a worst-case scenario, the lack of a correct load rating or the lack of a weight limit posting could allow heavier vehicles to cross and cause severe structural damage or the collapse of a bridge," the report stated.

But climb it does - just short of a lung-sapping five kilometres (three miles) above sea level, where even the internal combustion engine is forced to toil and splutter.

Then it pauses for a while on the snow-flecked crest of the Andes before pitching - like a giant white knuckle ride - into the abyss.

The road from Bolivia's main city, La Paz, to a region known as the Yungas was built by Paraguayan prisoners of war back in the 1930s.

Many of them perished in the effort. Now it is mainly Bolivians who die on the road - in their thousands.