Michigan Compiled Laws, Chapter 257. Motor Vehicles § 257.252k

(a) The notice shall be prominently displayed at each point of entry for vehicular access to the real property. If the real property lacks curbs or access barriers, not less than 1 notice shall be posted for each 100 feet of road frontage.

(b) The notice clearly indicates in letters not less than 2 inches high on a contrasting background that unauthorized vehicles will be towed away at the owner's expense.

(c) The notice provides the name and telephone number of the towing service responsible for towing or removing vehicles from that property.

(d) The notice is permanently installed with the bottom of the notice located not less than 4 feet from the ground and is continuously maintained on the property for not less than 24 hours before a vehicle is towed or removed.