Safety board suggests new risk studies of 68 U.S. bridges

The National Transportation Safety Board on Thursday recommended that the owners of 68 bridges in 19 states evaluate the strength of the structures. Officials suggested the studies as part of their ongoing investigation into the collapse of the Francis Scott Key Bridge in Baltimore which was struck by the containership Dali nearly one year ago. Officials found that before the collapse, the Key Bridge was nearly 30 times above a risk threshold established in 1991. The board said authorities would have been aware of the risk if the Maryland Transportation Authority had conducted a vulnerability assessment of the Key Bridge based on recent vessel traffic.

How urgent are their concerns? Federal officials did not suggest that all 68 bridges were certain to collapse but urged their owners to evaluate their vulnerability given modern standards. The Golden Gate Bridge, Brooklyn Bridge, Manhattan Bridge, Walt Whitman Bridge in Pennsylvania, and the Mackinac Bridge in Michigan all made the list of structures that could use a new risk assessment.

What guidelines does the board use to assess risk? The American Association of State Highway and Transportation Officials in 1991 developed a vulnerability assessment calculation for new bridges. Officials created the assessment after a freight vessel in 1980 collided with a column supporting the Sunshine Skyway Bridge in Florida. The incident killed 35 people when a large stretch of the bridge collapsed into Tampa Bay. All of the bridges on the NTSB’s list were built before the guidance was established.

Dig deeper: Read Josh Schumacher’s report about the U.S. reaching a $100 million settlement over the bridge collapse.