Started in 1931, The Highway Patrol Division (HPD) at Arizona is one of the largest divisions of the Arizona Department of Public Safety. It looks after the public safety as far as the use of highway transportation system is concerned. The department provides services and enforcement in commercial motor vehicle, tow truck, school bus enforcement and safety programs and also is responsible for the air rescue and aviation services. The Highway Patrol Division (HPD) operates through its four Patrol Bureaus, a Commercial Vehicle Enforcement Bureau and the Aviation Section.