Scripps News has learned the federal government is examining dozens of large bridges across the country in response to the collapse of the Francis Scott Key Bridge in Baltimore.
Shortly after the disaster, the Federal Highway Administration began collecting information about current and past efforts to protect piers supporting more than 100 bridges that carry vehicle traffic over major waterways.
The review is part of the National Transportation Safety Board's ongoing investigation of the Baltimore bridge failure.
The Key Bridge plummeted into the Patapsco River in March just outside one of the nation's busiest cargo ports, killing six road workers, after a loaded container ship lost steering power and smashed through a critical support pier.
A Scripps News investigation has found good reason to examine how often ships crash into bridges.
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An analysis of U.S. Coast Guard records of maritime incidents shows a vessel has run into part of a bridge in America at least 650 times since 2019.
Many of those bridges soar across the Mississippi River, a major shipping thoroughfare.
The Old Highway 80 Railroad Bridge in Vicksburg, Mississippi, is struck by barges sometimes multiple times a day, said Herman Smith, superintendent of the Vicksburg Bridge Commission of Warren County.
"It is the most-hit bridge on the river system," he said.
Smith said a sharp bend in the river and swift currents can make the stretch of the Mississippi, near the bridge, a challenge for boat captains trying to guide barges, tethered together, between two piers.
"You don't drive a boat like you do a car with a trailer," Smith said, noting it's almost impossible to steer barges straight down part of the river. "Here, they can't do that unless the water is really, really, really slow."
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One of the most banged-up pillars has been hit more than 200 times, earning it the nickname "Scar."
"If you look at it you can tell why," Smith said.
An up-close view shows inches of concrete scraped away by barges over the years, exposing steel rebar installed when the bridge was built almost 100 years ago.
Even though the bridge is frequently struck by vessels, Smith said he does not believe any have been large enough to take out a pillar.
"The concrete is 15 feet thick there," he said.
But even small vessels can threaten large bridges.
In 2018, a crane barge crashed into the deck of the Sunshine Bridge over the Mississippi River in Convent, Louisiana.
What looked like minor damage masked what engineers said was nearly a catastrophe.
A Coast Guard investigation noted that "by calculations ... the bridge should have ultimately failed and resulted in a bridge collapse."
The bridge in Vicksburg and the Key Bridge in Baltimore were built decades before national design standards spelled out how to build bridges capable of absorbing ship and barge strikes.
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Keeping standards up to date and relevant to all bridges is difficult, said Jason Hastings, vice chair of the Committee on Bridges and Structures at the American Association of State Highway and Transportation Officials, also known as AASHTO.
"I think there is a big issue with the constant change in the size of the ships as they continue to grow," Hastings said. "By the time that we are able to collect the data and get those standards passed, ships have grown beyond that."
AASHTO did not begin setting vessel collision standards until 1991, a decade after a cargo ship brought down the Sunshine Skyway Bridge in Tampa, killing 35 people.
Those standards, later adopted by the Federal Highway Administration, are mandatory in the design of new bridges only.
The federal government mostly leaves it to state and local authorities to decide how much protection older bridges need from ships and barges.
"The specs we have give some good procedures to bridge owners to evaluate risk associated with vessels," Hastings said. "We're constantly looking at our business practices and where our specs are lacking."
Herman Smith said the Coast Guard approached Warren County about installing bumpers to shield some of the piers supporting the Vicksburg bridge but did not identify a source of funding to pay for them.
Smith doesn't think they were necessary but stopped short of guaranteeing that a vessel strike could ever pull down the bridge he oversees.
"I cannot guarantee you anything," Smith said. "You put a pier in a river, it's going to get hit by something. Anything's possible, not very likely."
What remains unclear for the Vicksburg bridge, and many other older bridges around the country, is exactly how much force they can safely withstand from a wayward ship or barge.
Amy Fan contributed reporting to this story.