(1) Except as may be limited by law or these rules, a person who is otherwise within the definition of "motor carrier" under section 69-12-101 , MCA, and related provisions, and not otherwise exempt from regulation under section 69-12-102 , MCA, or related or similar provisions, is not a "motor carrier" if the transportation activities of the person are incidental to a principal business of that person.

(2) Transportation is incidental to a principal business when the transportation is in furtherance of, in the scope of, and subordinate to that principal business, as provided in these rules.

(3) The evaluation used to determine whether transportation is incidental under these rules may be referred to as the "primary business test."