How vulnerable is the Bay Bridge to a ship striking and collapsing it? NTSB, engineers want to know

Jean Marbella, Baltimore Sun on Mar 23, 2025

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BALTIMORE — It’s too late for the Francis Scott Key Bridge, but not for its longer and more heavily trafficked sibling span over the Chesapeake Bay.

The National Transportation Safety Board criticized Maryland on Thursday for failing to assess the risk of a ship striking and collapsing the Key bridge, which is exactly what happened nearly one year ago. But, the NTSB noted, Maryland also had not conducted the recommended assessment on its other major span, the Bay Bridge.

“Hindsight is 20/20,” said Michael Shields, a Johns Hopkins associate professor of civil and systems engineering. “The important thing now is we acknowledge the risk is there.”

He is among those gratified to learn that according to the Maryland Transportation Authority, an assessment of the Bay Bridge’s vulnerability to being struck and knocked down by a ship has been underway since the fall. Responding to the NTSB’s criticism, state transportation officials said it would have an update of its Bay Bridge within 30 days.

The NTSB identified 68 bridges across the country, including both the east- and west-bound spans of the Bay Bridge and the Chesapeake City Bridge, with an “unknown level of risk of collapse.” The NTSB recommends that the bridge owners calculate that risk under guidelines established by the American Association of State Highway and Transportation Officials, or AASHTO, and inform the federal agency of their findings.

The guidelines date back to 1991, and were developed for use in constructing new bridges, said Patricia Bush, AASHTO’s program manager for bridges and design. AASHTO later recommended that states use those provisions to assess the vulnerability of bridges that had been built before 1991, she said.

Among the factors that go into determining the risk a bridge faces are the location of its piers, its height clearance, the location of the shipping channel, the size and height of vessels that traverse it and even the flow and speed of the waterway itself, Bush said.

“There are a lot of variables,” she said. “It’s very detailed. The equation takes into account the importance of these variables.

“The assessment takes time and resources, to hire a consultant or do in-house,” Bush said. “The state departments of transportations are constrained in staffing and in funding.”

The collapse of the Key Bridge may spur owners of other bridges to now do the risk assessments, she and other engineers said.

“The bridge engineers I work with in the 50 states and Puerto Rico and the District of Columbia, they are very good at looking at mistakes that happened in the past and trying to make sure they don’t happen again.”

What happened with the Key Bridge is a tragedy and a lesson, said Mehdi Shokouhian, an associate professor in Morgan State University’s civil and environmental engineering department.

“I think after the collapse, I think many states are considering” assessing their risks,” he said. “This is something we really have to think about.”

For one thing, “many factors have changed” in the decades since the Key and Bay bridges were built, Shokouhian said.

Vessels are much larger and heavier, greatly increasing the impact force on a bridge in the event of a ship crashing into it, he said. The “dolphins” and “fenders” that many older spans have to prevent ships from crashing into bridge supports are too small to provide much protection against huge ships, he said.

The Dali, for example, weighed more than 112,000 metric tons when it left the Port of Baltimore in the early morning hours of March 26, 2024, lost power and crashed into the Key Bridge.

While assessing the vulnerability of bridges to collapse is recommended by AASHTO and the NTSB, it remains voluntary. But engineers say they hope states and other bridge owners will see the value of conducting such reviews.

“I think these risk assessments are essential especially in the wake of the Key Bridge collapse,” Shields said. “It is costly to do, and to put protective measures in place as a result of the risk assessments.”

And indeed, an evaluation of the Delaware Memorial Bridge’s fender system determined it needed more protection, and a project begun in 2023 has a nearly $100 million price tag.

“We have a choice of course,” Shields said. “The cost of the protective measure may be high, but you have to weigh that against the loss of life, the loss of the bridge, the loss of commercial traffic.

“I certainly hope that authorities across the country recognize the risk to these bridges,” he said, “and act accordingly.”