America’s bridges are in danger.

From one spanning the San Francisco Bay to the Chesapeake Bay Bridge here in Maryland, structures are much more prone to ship strikes than previously thought, Johns Hopkins University researchers have found.

Vessels are “highly likely” to collide with bridges in the U.S. — and “potentially catastrophic collisions” could happen every few years, according to preliminary findings released Monday.

Their research comes on the heels of an urgent assessment issued Thursday by the National Transportation Safety Board, prodding bridge owners across the country to study the risk of ship strike. Jennifer Homendy, the NTSB’s chair, scolded the Maryland Transportation Authority and bridge owners for failing to evaluate the dangers presented by ships, which are far larger today than in decades past.

The Hopkins research goes a step further than the NTSB’s latest warning, analyzing the actual risk of vessel collision at various bridges and ranking them by vulnerability.

Their revelations, the result of a federally funded assessment launched last year, underscore the surprising probability of bridge disaster. Hopkins identified 14 bridges that can expect a ship strike at least once in every 100 years.

In the immediate aftermath of the Francis Scott Key Bridge collapse a year ago, officials grappled with the unforeseen, one-in-a-million calamity. But the NTSB said the Key Bridge was 30 times more susceptible to collapse from a ship strike than it should have been, per the nation’s bridge code.

Hopkins researchers hope their data-driven study will encourage bridge owners to take actions to prevent similar catastrophes and, potentially, alter the U.S. bridge code.

Michael Shields, a Hopkins engineering professor who led the study, said that although the Key Bridge collapse was thought of as a “shocking aberration,” it is actually consistent with history.

“It’s something that, if we had prepared adequately for, we could have seen this type of thing coming,” he said.

Still, an extraordinary set of events led to the Key Bridge collapse. A 100,000-ton cargo ship, the Dali, lost power at the most inopportune time, striking a critical pier and bringing down the structure on March 26, 2024. Six construction workers who had been on the span were killed.

The Maryland Transportation Authority, which owns the Key Bridge and Bay Bridge, insisted Friday that the catastrophe was the “sole fault” of the Dali and “the gross negligence of its owners and operators who put profits above safety.”

The nation’s bridge code specifies that a “critical bridge,” a category that includes ones leading to major ports, should collapse from a ship collision less frequently than once every 10,000 years. The Hopkins researchers studied a slightly different question: How often will a bridge be hit by a large vessel, whether or not that leads to a collapse?

The bridge it found to be most at risk was the Huey P. Long Bridge, over the Mississippi River near New Orleans, which the analysis showed can expect to be hit by a ship on average once every 17 years. The San Francisco-Oakland Bay Bridge was second on the list, at risk of ship strike once every 22 years.

Researchers found that the fallen Key Bridge was likely to be hit once every 48 years. The Bay Bridge can be expected to be hit once over every 86 years.

The Bay Bridge has never been struck by a large vessel. Traffic on the bridge was briefly shut down last year, however, when a nearby ship had a steering problem before safely transiting under it.

“My hope with this study is that this motivates the proper authorities, the MDTA in this case, to investigate what the appropriate protections are and put them in place sooner rather than later,” Shields said.

Homendy slammed the transportation authority for failing to assess the Key Bridge and Bay Bridge for risk of ship strike.

An NTSB report released last week specified that bridge owners are not federally required to “complete a vulnerability assessment for a bridge designed” before 1991, when the bridge code was altered. Bridges built before then, including the fallen Key Bridge and the Bay Bridge, were merely “recommended” for assessment.

The authority has previously said it is studying the possibility of adding physical protections to the Bay Bridge. It told The Baltimore Banner it is “working with outside bridge experts to evaluate the pier protection systems” at both the Bay Bridge and the new Key Bridge.

As requested, the authority said it will provide an update regarding the Bay Bridge “to the NTSB within 30 days.”

The Hopkins research team analyzed ship tracking data back to 2009 — “hundreds of millions of data points,” Shields said.

It’s up to bridge owners to assess what type of protections might be required and whether they can afford the upgrades.

Maryland’s authority revealed an initial budget for protection at the Bay Bridge last year, estimating it would cost $145 million.

Modern bridges adhere to updated standards of safety. The new Key Bridge, for example, will have more robust pier protection and will have a longer main span — at least 1,600 feet — than the old one. The longer that span, the farther apart piers are from the shipping channel.

The Hopkins findings might surprise many who consider the Key Bridge collapse to have been a standalone event. But it is among roughly a dozen U.S. bridges that have been knocked down by a ship in the last 50 years.

“The historical precedent is there,” Shields said. “This is a repeating problem.”

Bridges most at risk of ship strike

• Huey P. Long Bridge, Louisiana: Collision expected once every 17 years.
• San Francisco–Oakland Bay Bridge: Collision expected once every 22 years.
• Crescent City Connection, New Orleans: Collision expected once every 34 years.
• Beltway 8 Bridge, Texas: Collision expected once every 35 years.
• Hale Boggs Memorial Bridge, Louisiana: Collision expected once every 37 years.
• Bayonne Bridge, N.Y./N.J.: Collision expected once every 43 years.
• Fred Hartman Bridge, Texas: Collision expected once every 47 years.
• Martin Luther King Bridge, Texas: Collision expected once every 64 years.
• Sunshine Bridge, Louisiana: Collision expected once every 71 years.
• Rainbow Bridge, Texas: Collision expected once every 71 years.
• Veterans Memorial Bridge, Louisiana: Collision expected once every 74 years.
• Chesapeake Bay Bridge, Maryland: Collision expected once every 86 years.
• Talmadge Memorial Bridge, Georgia: Collision expected once every 88 years.
• Veterans Memorial Bridge, Texas: Collision expected once every 94 years
• Source: Johns Hopkins University assessment