Mich. Comp. Laws § 247.440

Sec. 40. All highways improved under the provisions of this act by the county road commissioners, or by the state highway commissioner, where more than 1 county is affected, that are parts of county roads shall be and remain under the jurisdiction of the county road commissioners of the county in which such highway is situate. Any township road improved hereunder shall be and remain subject to the jurisdiction or authority of the proper township officials after such improvement: Provided, however, That in all cases, the jurisdiction of the county and township officials shall be subject to the right to make proper repairs out of the maintenance fund, if any, hereinbefore provided for. In any highways improved along a county line, jurisdiction over the portion improved shall remain the same as though no improvement had been made upon such highway.