Mich. Comp. Laws § 254.54
In those counties in which the county road system, so-called, shall have been adopted, the board of supervisors shall upon the ordering of any such bridge duly certify such action to the county road commissioners of such county. Thereupon the said county road commissioners shall promptly proceed to establish a road district for the purpose of constructing or reconstructing such bridge. Said commissioners shall have authority to procure, if need be, any further surveys, plans, specifications and estimates of cost for such work of construction or reconstruction in addition to those which may have been obtained by the said board of supervisors. Such specifications shall not be final, but may be changed by the county road commissioners, but not after the hearing of objections hereinafter provided for, except after due notice and hearing thereon: Provided, Said road commissioners shall not at any time change the type of bridge ordered by the board of supervisors.
MCL 254.54