The Mackinac Bridge Authority (MBA) shared a recent report from its consulting firm that confirms the bridge is at a lower risk of collapse due to a vessel collision than nationally established thresholds. The study was submitted to the National Transportation Safety Board (NTSB) in March, and the MBA reviewed the study conclusions this week at its meeting.
Background:
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- Following the March 2024 collapse of the Francis Scott Key Bridge in Baltimore after it was struck by a container ship, the NTSB called on owners of 68 bridges to evaluate the structures for risk of collapse.
- The NTSB asked the bridge owners to conduct a vulnerability assessment to determine the risk of collapse.
Key Points:
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- The NTSB recommended owners calculate the annual frequency of collapse of their bridges using specific industry guidelines.
- The total annual frequency of collapse refers to the risk of structural failure, in this case, due to a collision.
- The Mackinac Bridge’s annual frequency of collapse was well below the American Association of State Highway and Transportation Officials limit.
- By comparison, the NTSB found that the Key Bridge was almost 30 times above the acceptable risk threshold for critical or essential bridges.
