As used in this article, the term:

(1) "Motor carrier" means any person who operates or causes to be operated any motor vehicle, as defined in this Code section, on any highway in this state.

(2) "Motor fuel" means any liquid, regardless of its composition or properties, used to propel a motor vehicle.

(3) "Motor vehicle" means any passenger vehicle that has seats for more than 20 passengers in addition to the driver and any vehicle or combination of vehicles used, designed, or maintained for transportation of property and having two axles and a gross vehicle weight exceeding 26,000 pounds or having three or more axles regardless of weight. The term "motor vehicle" does not mean:

(A) School buses;

(B) Vehicles operated by the state, any political subdivision of the state, or the United States; or

(C) Transit buses operated exclusively within this state.

(4) "Operations" means operation of any motor vehicle, whether loaded or empty, whether or not for compensation, and whether owned by or leased to the motor carrier who operates it or causes it to be operated.