[voltdr]

I found this online.

Michigan
Any Michigan resident who intends to operate the following commercial vehicles is required to have a commercial driver license:

Single Vehicles - Having a gross vehicle weight rating (GVWR)* of 26,001 pounds or more.



Combination Vehicles - Towing a trailer or other vehicles with a GVWR of 10,001 pounds or more when the gross combination weight rating (GCWR)** is 26,001 pounds or more.



Vehicles:

Designed to transport 16 or more people (including the driver)
Carrying hazardous materials in amounts requiring placarding