truck drivers are persons employed as the operator of a cmv. cmvs can be of varying shapes and sizes, from pickup trucks assigned to haul specialized or small quantities of freight, all the way up to semi-trailer trucks. trucks are assigned a class rating based upon the gross vehicle weight rating (gvwr). the facts in this section refer to drivers of "heavy duty" trucks (with a gvwr of at least , which require a commercial driver's license to operate).