Michigan Compiled Laws, Chapter 257. Motor Vehicles § 257.611a

(a) The department of transportation, the local authority, or the county road commission, within its respective jurisdiction, authorizes that owner or employee to direct traffic due to safety or work requirements. The authorization shall be issued in the manner considered appropriate by the department of transportation, the local authority, or the county road commission, and may be general or specific. The authorization may establish the conditions under which the owner or employee may direct traffic, and may allow the owner or employee to direct traffic in disregard of an existing traffic control device.

(b) The owner or employee is properly trained, equipped, and attired in conformance with the manual of uniform traffic control devices authorized under section 608.  1