Mich. Comp. Laws § 221.20
All highways regularly established in pursuance of existing laws, all roads that shall have been used as such for 10 years or more, whether any record or other proof exists that they were ever established as highways or not, and all roads which have been or which may hereafter be laid out and not recorded, and which shall have been used 8 years or more, shall be deemed public highways, subject to be altered or discontinued according to the provisions of this act. All highways that are or that may become such by time and use, shall be 4 rods in width, and where they are situated on section or quarter section lines, such lines shall be the center of such roads, and the land belonging to such roads shall be 2 rods in width on each side of such lines.
MCL 221.20