Michigan Compiled Laws, Chapter 254. Bridges § 254.371

Sec. 11. At such time as the refunding bonds authorized by this act are retired in full, the Mackinac bridge shall be operated by the state highway department as a part of the state highway system and all expenses in connection with the operation and maintenance of the bridge shall be paid in the same manner as similar expenses in connection with the state highway system are paid. If authorized by law, the commission may charge and collect tolls, fees, rents and charges for the use of the bridge to provide all or any part of the costs of operation and maintenance of the bridge.