The AZ Highway Patrol, like many other state patrols, started within the Arizona Dep't. of Transportation. Because of Arizona law regarding the primacy of the Office of Sheriff within the county and the resistance of those Sheriffs to allowing a State Police agency, in 1969, the Arizona Highway Patrol was transferred to and re-booted as a division of the AZ Department of Public Safety. This change forced the scope of the new agency to consider not just the State Routes and Interstates, but now Statewide law enforcement communications and the emerging field of emergency medical services. AZ DPS migrated to UHF in the early 1970s and each of the districts was on UHF channels by 1975. EMSCOM was also in the UHF band and that helped drive the entire transition to UHF, as well as making a tidy profit for Motorola. The VHF channels were left for CID and other DPS divisions. Statewide VHF was still around in the early 1980s and then disappeared as it was portioned out to small towns and counties that lacked the funds or the tax base for upgraded comms.
I read a lot of AZ DPS Annual Reports from these years, talked to DPS dispatchers who were assigned to their respective districts before being consolidated in Phoenix, Tucson, and Flagstaff; was friends with a lot of old timers like Terry DeBoer  and his wife Diane [a dispatcher during the period], Bob Martin , Ed Rebel , Paul Johnson , Harry Miller , and others I can't recall right now.