While Arizona has rules regarding seatbelts and child restraints inside vehicles, the state has no specific laws addressing the legality of passengers riding in the bed of a pickup truck. This article explains the legality and nuances of the transportation of passengers and pets in the back of a pickup truck.
Arizona's seatbelt law requires all front-seat passengers and children under 16 years old to be properly restrained. However—apart from a few special rules for child care facilities and foster homes—the law doesn't prohibit persons 16 years and older from riding in the bed of a pickup truck.
Having a truck-bed passenger won't lead to a traffic violation fine but could result in civil liability or insurance costs if anyone is injured in an accident.
Just as there are no restrictions on people in truck beds, Arizona doesn't prohibit the transportation of animals in truck beds. However, the American Veterinary Medical Association recommends that pets be secured either by a kennel in the truck bed or by a harness inside the cab.