Mich. Comp. Laws § 247.656
Within 6 months from the effective date of this act, a tentative system of major streets shall be selected in each incorporated city and village of the state and certified to the state highway commissioner for his approval. Such tentative system of major streets shall be selected in each incorporated city and village under the direction of the governing body thereof on the basis of greatest general importance to such municipality and shall not include any of the trunk line highways or county roads within the limits of such municipality. Each such tentative system of major streets certified to the state highway commissioner shall be checked and reviewed under his direction. Within 6 months after receipt by him of each such certification the state highway commissioner shall approve such part of that tentative system of major streets as complies with the uniform standards and specifications adopted and established as hereinbefore provided and shall reject and delete any part that does not so comply and shall certify to that city or village the approved portion of the tentative system and any deletions therefrom. So much of the tentative system of major streets of any city or village as is approved by the state highway commissioner shall constitute the major street system of that municipality for all purposes, and shall be known officially as the major street system of that city or village as the case may be.
MCL 247.656