The Mackinac Bridge will likely remain structurally sound if a ship were to strike one of its piers, according to a new study commissioned by the Bridge Authority.
The analysis was conducted by the engineering firm Parsons in response to the collapse of Baltimore-area Francis Scott Key Bridge in 2024. A container ship struck one of the bridge's piers in the middle of the night, killing six people in the collapse.
Federal transportation officials requested a review of how the Mackinac Bridge would handle a similar incident. Researchers concluded the Mackinac Bridge is at low risk of collapsing if a vessel collided with it.
“We all believed for a long time that this is the case," said Kim Nowack, director of the Mackinac Bridge Authority.
She says analysts investigated how the bridge would handle a variety of vessels.
"Everything from the big thousand-foot freighters down to the smaller, more like a cruise ship type thing or a tugboat type thing," she said.
The Mackinac Bridge was one of 68 bridges across 19 states asked to conduct collision studies by the National Traffic Safety Board.
Those bridges were all built prior to the current safety guidelines established by the American Association of State Highway and Transportation Officials in 1991. The Mackinac Bridge was built in 1957.
Nowak says there are key differences between the Mackinac Bridge and the Key Bridge.
“We don't see that same kind of vessel traffic," Nowak said. "We don't see those large container ships here. Our vessels are smaller and our opening underneath the shipping channel is huge. It's a 3,000-foot opening."
The Key Bridge was built in 1972, 19 years before the AASHTO published its guidelines. The NTSB found that the bridge was close to 30 times above the acceptable risk threshold for bridges deemed "essential."
