MACKINAC ISLAND, MI – A recent study determined that the risk of the Mackinaw Bridge collapsing after a vessel bridge strike is low. The Mackinac Bridge Authority confirmed the bridge is at a lower risk of collapse due to a vessel collision than nationally established thresholds, the bridge authority announced on Wednesday, July 8.
The assessment, conducted by a consulting engineering firm Parsons, was made after the Mackinac Bridge was selected by the National Transportation Safety Board (NTSB) to be evaluated for risk of bridge collapse in March 2025.
The Mackinac Bridge is the only one in Michigan on the list. Others — Zilwaukee, Blue Water, International and Gordie Howe bridges — were left off the list because they have piers on land (and are protected from strikes), aren’t high enough for ocean-going vessels to travel under or were built recently enough to meet current protection standards.
“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,” said Bridge Director Kim Nowack. “We hope this gives greater assurance to everyone who crosses the bridge that there is very little danger of such a tragedy here.”
Mesabi Miner approaches the Mackinac Bridge on her way to Duluth-Superior. – Mike Rezabek
The report is in response to a request from the NTSB to 30 owners of 68 spans in the U.S., recommending that each conduct a vulnerability assessment.
The recommendations by the NTSB were issued to bridge owners using the American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications and Commentary for Vessel Collision Design of Highway Bridges.
The analysis determined a total annual frequency of collapse of 0.000097, corresponding 0.0001 for critical bridges, officials said.
Read the entire article at: Detroit Free Press: Mackinac Bridge
