Mich. Comp. Laws § 247.351

Sec. 1. The township board of any township and the board of county road commissioners in which said township is located are hereby authorized and shall have power to enter into a contract to provide for the acquisition, construction, establishment, opening, altering, improving and maintaining of any highways within the township. Said highways shall be deemed to include such bridges, culverts, storm sewers and other drainage structures, and traffic control and regulatory devices, as may be necessary to provide a complete highway.