More than 80,000 bridges across the United States are in dire need of repair.

That number comes from the Associated Press, which conducted an analysis of the National Bridge Inventory and found 65,505 bridges have been classified as "structurally deficient" and 20,808 have been designated as "fracture critical."

For motorists, there is plenty of reason to be concerned.

"You have a legal, moral and ethical obligation as stewards of the traveling public not to let people go over something that's unsafe," author Barry LePatner tells the Wall Street Journal.

Of the flagged bridges, 7,795 fall into both categories of "structurally deficient" and "fracture critical". Experts tell the AP that's a "combination of red flags." More than 400 of the crossings score less than a 10 on a 100-point sufficiency scale that the federal government uses to prioritize bridge replacement.

"It's kind of like trying to predict where an earthquake is going to hit or where a tornado is going to touch down," said Kelly Rehm, bridges program manager for the American Association of State Highway and Transportation Officials.

Some of the affected bridges are the most iconic and well-traveled bridges in the country, including the Brooklyn Bridge, the Frederick Douglass Memorial Bridge in Washington D.C., the Davison Bridge in Detroit and the Tappan Zee Bridge, which connects Rockland County to Westchester County in New York.

In May, a bridge that was part of Interstate 5 north of Seattle collapsed into the Skagit River. Nobody was killed. Many bridges across the country were constructed between the 1950s and 1970s at the onset of the interstate highway system, and they're now past their intended lifespans.

Aging bridges are concerns to both consumers and manufacturers. On Tuesday, a coalition of businesses across the country released a survey that said the country's crumbling infrastructure will hamper the economy. The majority of more than 400 manufacturers say American infrastructure is in "fair" or "poor" shape, and roads in particular are getting worse.

"Improving our ports, highways and bridges is essentially an economic driver," former Pennsylvania Gov. Ed Rendell said in a written statement. Modernizing would "enable American manufacturers and businesses to export their goods to countries around the world, which strengthens our economy here at home."

Last week, the American Society of Civil Engineers released a report that gave the U.S. an overall infrastructure grade of D+, which included roads, bridges, damns, water supply, energy and aviation. It said more than 200 million motorists cross structurally deficient bridges each day in the nation's 102 largest metro areas.

There are 607,380 bridges in the National Bridge Inventory, and 14.2 percent fall into either the "structurally deficient" or "fracture critical" categories.

The engineers projected that America needs to invest $3.6 trillion by 2020 to maintain a state of good repair.

"Our outdated roads, ports and inland waterways are in desperate need of repair and continue to add costs and complications," National Association of Manufacturers president Jay Timmons said.