America's bridges are in rough shape.
More than a third of the nation's bridges are in need of repair, and over 43,000 are in poor condition and classified as "structurally deficient," according to the American Road & Transportation Builders Association.
A structurally deficient bridge is one that requires significant maintenance to remain in service. It is often posted with weight limits but is considered safe to use.
Each day about 167 million trips are taken across structurally deficient bridges in the U.S.
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"The state of bridges in the U.S. is not good, and we're losing the battle," said William Ibbs, a civil engineering professor at the University of California Berkeley.
Hours ahead of President Joe Biden's scheduled visit to Pittsburgh in January to discuss infrastructure, one of the city's more than 440 bridges collapsed. Ten people were injured including first responders.
Other bridges collapsed in Washington state in 2013 and Minneapolis in 2007.
"I think what we found is that we deferred maintenance for a long time, and then all of a sudden, we're at the point where we have this big backlog of maintenance that we have in, and we don't really have the funding to catch up at this point," said Kevin Heaslip, a civil and environmental engineering professor at Virginia Tech.
While most of the country's structures were designed for a service life of about 50 years, the average age of bridges in the U.S. is 44 years. Older bridges with fewer lanes and restricted access can add to congestion impacting commerce and the response time of emergency services.
But after innovations in bridge building, new building materials and additional funding, there are signs of some modest improvement for the nation's bridge inventory.
In January, Biden announced his administration would distribute $27 billion over the next five years to fix or rebuild thousands of the nation's bridges. The current estimate to repair all bridges in the U.S. is $125 billion, according to the American Society of Civil Engineers.
So why are so many of the nation's bridges in a state of disrepair, and what steps are being taken to fix them? Watch the video to learn more.