Mich. Comp. Laws § 255.53
The board of county road commissioners of any such county is hereby authorized to accept any such ferry, equipment and services and to operate and maintain ferry services in such manner and subject to such rules, regulations and tolls as said board of county road commissioners may see fit, from time to time, to fix and adopt. Said services may be furnished free to the public, or charges and tolls may be exacted. If charges and tolls are exacted, they shall be on the basis of cost, including capital investment, maintenance, operation, interest on investment, and depreciation.
In the event the highway adjacent to said ferry is acquired by the state highway commissioner of the state of Michigan, then and in that event said state highway commissioner is authorized to acquire, own, operate and maintain said ferry and ferry services in the place and stead of said board of county road commissioners and with like rights and authority.
MCL 255.53