BALTIMORE — A sobering report from Johns Hopkins University engineers has identified 20 major U.S. bridges at significant risk of ship collisions that could lead to collapses similar to the Francis Scott Key Bridge disaster in Baltimore on March 26, 2024. Released on March 24, 2025, the study underscores a heightened vulnerability driven by increased shipping traffic and larger vessels, challenging the assumption that such incidents are rare. The findings suggest that some of the nation’s busiest bridges could face a major strike within decades, prompting urgent calls for protective measures.
The investigation, led by Michael Shields, a Johns Hopkins engineer specializing in risk assessment, analyzed 16 years of U.S. Coast Guard shipping data—hundreds of millions of data points—cross-referenced with the National Bridge Inventory. The team found that while bridge design standards aim for an annual collapse probability of less than 1 in 10,000, historical data shows 17 major bridge collapses from ship strikes between 1960 and 2011, averaging one every three years. “With this investigation, we wanted to know if what happened to the Key Bridge was a rare occurrence. Was it an aberration? We found it’s really not,” Shields said. “In fact, it’s something we should expect to happen every few years.”
Topping the list is the Huey P. Long Bridge in Louisiana, with a projected collision every 17 years, followed by the San Francisco-Oakland Bay Bridge at 22 years, and the Crescent City Connection in New Orleans at 34 years. The Delaware Memorial Bridge, a critical link on the I-95 corridor between Delaware and New Jersey, ranks 15th with an expected strike every 129 years. Other notable bridges include the Golden Gate Bridge (481 years) and the Chesapeake Bay Bridge (86 years). The study estimates the Key Bridge, which stood for 46 years, would have been among the 10 most vulnerable, likely facing a strike within 48 years.
The report highlights a stark mismatch between modern maritime realities and aging infrastructure. Many bridges, built decades ago, were not designed to withstand today’s mega-freight ships, like the 984-foot Dali that felled the Key Bridge. “To keep our bridges safe and operational, we want the chances of a collision strong enough to take down the bridge to be less than one in 10,000 in a given year, not one in a 100,” Shields said. “One in 100 is extremely high. If I look at the San Francisco Bay Bridge, we’re likely to see a major collision once every 22 years. That is huge.”
Despite the alarming frequencies, Shields noted that a collision doesn’t guarantee collapse. “No two bridges are the same,” he said, pointing to factors like pier placement and protective systems. The team recommends installing “dolphins”—concrete barriers to deflect ships—as seen on the Sunshine Skyway Bridge in Florida after its 1980 collapse. The Delaware River and Bay Authority is already investing $19.1 million in such protections for the Delaware Memorial Bridge, per the Philadelphia Inquirer.
The study, funded by a National Science Foundation Rapid Response grant, comes as the nation marks one year since the Key Bridge tragedy, which killed six workers. Preliminary findings released in summer 2024 identified high-traffic bridges, but this full report, available at bridgerisk.engineering.jhu.edu, ranks specific vulnerabilities. It aims to guide policymakers, with rebuilding the Key Bridge estimated at $1.7 billion to $1.9 billion and retrofitting others potentially costing billions more.
As shipping grows—global trade has surged since the 1970s, per the Johns Hopkins Hub the urgency to act intensifies. The team hopes its data will prioritize infrastructure investments, reducing risks that current standards underestimate.
