(CNN) -- Nearly a quarter of the nation's roughly 600,000 major bridges carry more traffic than they were designed to bear, according to reports based on federal government data.
The Interstate 35W bridge collapsed into the Mississippi River during rush hour Wednesday.
Experts said Thursday that the problem stems from a lack of money and leadership.
Federal Highway Administration data from 2006 shows that 24.5 percent of the nation's bridges longer than 20 feet were categorized as "structurally deficient" or "functionally obsolete" (data from Utah and New Mexico was from 2005).
"Our bridges are not in very good condition in this country," said Ruth Stidger, editor in chief of the trade publication Better Roads, which compiled the data. See a list of bridges that the Transportation Department wants inspected (pdf)
Some states are worse than others. Arizona and Rhode Island have a similar number of structurally deficient or functionally obsolete bridges -- 384 and 405 respectively. In Arizona, however, that's 5 percent of its total bridges, while in Rhode Island, it's more than half. See how many problem bridges are in your state »
While the "structurally deficient" and "functionally obsolete" monikers don't indicate the crossings are treacherous, they do imply serious problems, Stidger said.
The Interstate 35W bridge that collapsed into the Mississippi River during Wednesday rush hour was deemed structurally deficient two years ago.
Recent inspections did show "concerns about stress and fatigue" in aspects of the bridge but did not result in calls for immediate restrictions on the bridge, Minnesota Gov. Tim Pawlenty said Thursday. See photos of the disaster »
Structurally deficient, Stidger said, generally means the bridge can't carry the traffic it was designed to accommodate. Usually, restricting traffic to light vehicles can alleviate any dangers.
Functionally obsolete is a different story, Stidger said, explaining that bridges carrying this tag also carry major design problems, diminishing their load-carrying capacity. Functionally obsolete bridges "probably should be replaced," she said.
In its most recent report card on the nation's infrastructure, the American Society of Civil Engineers gave the nation's bridges a grade of "C" and said that in 2003 27.1 percent of them were deficient. Watch why some bridges need repairs »
Casey Dinges, a staff leader on the report card, said "structurally deficient" and "functionally obsolete" are technical terms used by the federal government.
"Neither one means failure is imminent or that your life is in danger or that you should be afraid to get in your car," he said. "That said, we still have pretty serious concerns about the overall state of the nation's infrastructure."
The report also said bringing all the nation's bridges up to snuff would cost $188 billion over the next two decades.
While the number might sound staggering to some, Dinges says it's "doable."
"That's simply maintaining what we are doing right now," he said.
"New technology, money -- there are resources involved, but I think the big thing is really political leadership, and that has to come at all levels of government," he said.
"There has to be an honest discussion about the financial resources it takes to maintain these systems," he said, adding that infrastructure needs to be a priority.
"There are no Republican bridges. There are no Democratic drinking water purification facilities. We all use these systems," he said.
But Stidger said states aren't getting the money they need to repair their roads and bridges. They're forced to resort to a process of "patch, patch, patch and nothing ever gets repaired," she said.
She likened the process to putting a Band-Aid on a broken elbow and said, "There's only so much you can do with inadequate funding."
The bulk of Highway Trust Fund revenue comes from an 18.4-cents-a-gallon federal gasoline tax. The fund is the primary source of federal money for transportation infrastructure and the interstate highway system.
That tax has not been adjusted since 1993, despite inflation and sharp increases in construction costs, according to the fund's Web site.
"In the eyes of many, political resistance to raising the tax, or indexing it to inflation, remains almost insurmountable in the current climate," the Web site states.
The fund suggests exploring alternative sources of revenue, including tolls, public-private partnerships or a mileage-based tax.
But even if all the money Congress has approved from transportation improvements was doled out to the states, it still would not be enough, Stidger said.
The latest numbers show that of the nation's 595,185 bridges longer than 20 feet, 145,996 have some sort of problem.
So, should the state of the nation's roads and bridges strike fear into the heart of the American commuter?
"Normally, I would say no," Stidger said, "but if I lived in Minnesota and drove over that bridge every day, I would not be a happy camper."
Overall, city, state and county engineers do a fine job inspecting bridges, reporting deficiencies and addressing those deficiencies with the resources they have, Stidger said.
But as Wednesday's tragedy demonstrated, sometimes those efforts are insufficient.
The Interstate 35W bridge was under repair when it suddenly collapsed in a manner that left engineers familiar with the bridge baffled. See a map of the bridge »
"I am totally puzzled as to why both ends of the bridge would come down all at once," said Ted Galambos, a University of Minnesota engineering professor. "I don't think it was overload, so it could have been either some fatigue, failure or some sudden buckling that would cause the failure."
The Federal Highway Administration says this would be only the second bridge to fail for structural reasons in 20 years. The agency said most bridges are safe and those that should be closed will be.
Additionally, the House on Friday voted to direct $250 million in emergency spending for the Interstate 35W bridge. States are usually limited to $100 million for such emergencies, which is why the legislation is needed. A similar bill is pending in the Senate.
"You can't not deal with it. Bridges have to perform," Dinges said.
"We're seeing this as a wake-up call. It's time to stop hitting the snooze button." E-mail to a friend
CNN's Kristi Keck contributed to this report.