Mich. Comp. Laws § 257.7a

Sec. 7a. (1) "Commercial motor vehicle" means a motor vehicle or combination of motor vehicles used in commerce to transport passengers or property if 1 or more of the following apply: (a) It is designed to transport 16 or more passengers, including the driver. (b) It has a gross vehicle weight rating or gross vehicle weight, whichever is greater, of 26,001 pounds or more. (c) It has a gross combination weight rating or gross combination weight, whichever is greater, of 26,001 pounds or more, inclusive of towed units with a gross vehicle weight rating or gross vehicle weight, whichever is greater, of more than 10,000 pounds. (d) A motor vehicle carrying hazardous material and on which is required to be posted a placard as defined and required under 49 CFR parts 100 to 199. (2) A commercial motor vehicle does not include a vehicle used exclusively to transport personal possessions or family members for nonbusiness purposes.