Persons operating vehicles, or combinations of vehicles, in the transportation of hazardous material and subject to this division, shall carry in the vehicle while en route any shipping papers required to accompany the vehicle in accordance with regulations adopted pursuant to Section 2402. The bill of lading or other shipping paper shall be displayed upon demand of any member of the California Highway Patrol or any police officer of a city who is on duty for the exclusive or main purpose of enforcing the provisions of this code.