Nothing in this act shall apply to any vehicle operated by or for: (a) This state or any of its agencies or subdivisions, or (b) the United States or any of its agencies, or (c) any agency of two or more states, or (d) any agency of one or more states and the United States. Nothing in this act shall apply to any school bus as defined by the laws of this state operated by, for or on behalf of a state, any subdivision thereof, or any private or privately operated school or schools. Nothing in this act shall apply to any vehicle having farm registration issued under authority of Kan. Stat. Ann. § 8-143, and amendments thereto.