The Lead Off
- A new engineering report found the Mackinac Bridge faces an extremely low risk of collapsing if struck by a vessel, according to the Mackinac Bridge Authority.
- The assessment was completed following a recommendation from the National Transportation Safety Board after the 2024 collapse of Baltimore’s Francis Scott Key Bridge.
- Engineers concluded the bridge’s risk level falls well below nationally accepted safety thresholds established for critical bridges.
LANSING,MI (WOWO) A new engineering assessment has concluded the Mackinac Bridge faces a significantly lower risk of collapse from a vessel collision than nationally established safety thresholds, according to findings reviewed Wednesday by the Mackinac Bridge Authority during its regular board meeting.
The report was prepared in response to a recommendation issued by the National Transportation Safety Board (NTSB) following the March 2024 collapse of the Francis Scott Key Bridge in Baltimore after it was struck by the cargo ship Dali. The NTSB requested owners of 68 bridges across 19 states complete vulnerability assessments to evaluate the potential risks posed by vessel collisions.
Engineering study finds low collapse risk
According to WILX – The Mackinac Bridge Authority said engineers evaluated multiple factors during the assessment, including the bridge’s structural design and capacity, the navigational conditions within the Straits of Mackinac, and the size, type and frequency of vessels traveling beneath the span.
According to the completed report, the bridge’s calculated risk of collapse from a vessel strike is well below the nationally accepted limits established by the American Association of State Highway and Transportation Officials (AASHTO) for critical and essential bridges.
Bridge Director Kim Nowack said the findings support what bridge officials have maintained for years.
“This report confirms what we’ve long believed to be true, that the risk of the Mackinac Bridge collapsing due to being struck by a vessel is extremely low,” Nowack said. “We hope this gives greater assurance to everyone who crosses the bridge that there is very little danger of such a tragedy here.”
Assessment followed national safety review
The vulnerability assessment was part of a broader national effort initiated after the collapse of Baltimore’s Francis Scott Key Bridge in March 2024.
Following that incident, the NTSB recommended bridge owners evaluate whether existing structures meet current standards for vessel collision risk and determine whether additional protective measures may be necessary.
The Mackinac Bridge was among dozens of bridges identified for review.
Comparison with Baltimore bridge
According to the report discussed Wednesday, the Mackinac Bridge’s calculated risk falls comfortably below the thresholds established under AASHTO guidance.
By comparison, the NTSB previously determined the Francis Scott Key Bridge’s vessel collision risk was nearly 30 times higher than the acceptable threshold established for critical or essential bridges before its collapse.
The Mackinac Bridge Authority said the engineering findings indicate the Mackinac Bridge does not present a comparable level of vulnerability.
What engineers evaluated
The engineering review considered several factors affecting vessel collision risk, including:
- The bridge’s original design and structural capacity.
- Navigation conditions within the Straits of Mackinac.
- The size and types of commercial and recreational vessels using the waterway.
- The frequency of vessel traffic passing beneath the bridge.
Officials said those factors were incorporated into nationally recognized engineering methods used to calculate the bridge’s overall vulnerability.
Next steps
The Mackinac Bridge Authority has reviewed the engineering findings as part of its regular oversight responsibilities. The completed assessment satisfies the recommendation made by the National Transportation Safety Board following the 2024 Baltimore bridge collapse. Officials have not announced any additional structural changes or mitigation measures based on the report.
The Takeaway
- A new engineering assessment concluded the Mackinac Bridge’s risk of collapse from a vessel collision is significantly below nationally accepted safety thresholds.
- The study was completed after the National Transportation Safety Board asked bridge owners nationwide to conduct vulnerability assessments following the 2024 collapse of Baltimore’s Francis Scott Key Bridge.
- Bridge officials say the findings provide additional assurance that the Mackinac Bridge remains structurally resilient against vessel strikes under current engineering standards.
