The National Transportation Safety Board (NTSB) found that Baltimore’s Francis Scott Key Bridge, which collapsed after being struck by the container ship Dali on March 26, 2024, was almost 30 times above the acceptable risk threshold for critical or essential bridges, according to guidance established by the American Association of State Highway and Transportation Officials (AASHTO).
Over the last year, the NTSB identified 68 bridges that were designed before the AASHTO guidance was established — like the Key Bridge — that do not have a current vulnerability assessment.
The recommendations are issued to bridge owners to calculate the annual frequency of collapse for their bridges using AASHTO’s Method II calculation.
The NTSB urges 30 owners of 68 bridges across 19 states to conduct a vulnerability assessment to determine the risk of bridge collapse from a vessel collision. The latest NTSB report does not suggest that the 68 bridges are certain to collapse, but recommends that these 30 bridge owners evaluate whether the bridges are above the AASHTO acceptable level of risk.
In the case that the risk level is above the AASHTO threshold, the NTSB recommends that bridge owners develop and implement a comprehensive risk reduction plan.
According to NTSB report’s findings, if the Maryland Transportation Authority (MDTA) had conducted a vulnerability assessment on the Key Bridge, it would have been aware that the Key Bridge was above the acceptable risk and would have had information to proactively reduce the bridge’s risk of collapse.
The NTSB is also recommending that the Federal Highway Administration (FHWA), the US Coast Guard and the US Army Corps of Engineers establish an interdisciplinary team to provide guidance and assistance to bridge owners on evaluating and reducing the risk, which could mean infrastructure improvements or operational changes.
