Mich. Comp. Laws § 247.669
The board of county road commissioners in each of the several counties shall, within 1 year from the effective date of this act, complete the taking over as county roads of all roads, streets and alleys heretofore required to be taken over as county roads by the provisions of Act No. 130 of the Public Acts of 1931, as amended, being sections 247.1 to 247.13, inclusive, of the Compiled Laws of 1948. Said board of county road commissioners in each of the several counties shall take over as county roads all streets and alleys lying outside the limits of incorporated cities and villages and dedicated to the public in recorded plats approved by said board of county road commissioners, within 30 days after the recording of the plat or the effective date of this act, whichever may be the later. Such dedicated streets and alleys, when taken over by the county road commission, shall be county roads in all respects and for all purposes and shall be classified as county primary roads or county local roads pursuant to the provisions of this act.
MCL 247.669