Height Misjudgment Resulted in Crane Colliding with Bridge

The US National Transportation Safety Board (NTSB) has determined that a lack of proper identification of a crane’s height led to a collision with the Mackinac Bridge near Mackinaw City, Michigan. The incident occurred on May 7, 2023, when the towing vessel Nickelena was transporting a deck barge carrying a crawler crane through the Straits of Mackinac. The crane boom struck the bridge, causing damage estimated at $145,000 to the bridge and $665,000 to the crane, but fortunately, there were no injuries or pollution reported.

The towing company managers had visually estimated the crane boom angle to be between 50° and 60° before departure, believing it was safe for transit under the bridge. However, investigators later found that the actual boom angle was about 62°, making the crane about 10 feet too high to pass under the bridge’s 153-foot vertical clearance. The lack of a proper navigation assessment and verification of the tow’s safety before departure contributed to the collision.

Towing vessel operations are required to have a Towing Safety Management System (TSMS) in place to ensure safe operations. Despite claiming to have a TSMS, the vessel owners did not conduct a navigation assessment before departure, and the captain did not take additional actions to verify the tow’s safety. The NTSB emphasized the importance of accurate data and consultation of navigational resources when planning voyages involving high air draft vessels like crane barges to prevent similar incidents in the future.

Source