Mich. Comp. Laws § 247.292
No highway shall be closed under the provisions of this act until suitable detours around the same, or the closed portion thereof, are provided and are placed in reasonably safe and passable condition for traffic. Notices in the form of plainly legible signs shall be placed by the highway officials having such work in charge at either end of the closed highway or portion of highway and at such intermediate points along the detour, or detours, as may be necessary to plainly mark the same. Upon the completion of the work of construction, improvement or repair and as soon as the highway or bridge constructed, improved or repaired shall be in suitable condition for public travel, all barriers, marks and signs whatsoever erected under the provisions hereof shall be at once removed by the officials erecting or placing the same.
MCL 247.292