Between 1956 and 1961, ACTION purchased 52 AEC Reliance buses with body by Commonwealth Engineering, Granville NSW. These buses were fitted with a mid-underfloor-mounted 7.7-litre AEC AH470 engine and a five-speed syncromesh gearbox.
The first of these buses was registered as C.0001, a new Commonwealth numberplate series reserved for Canberra Buses. This series was later re-issued with ZIB- plates, although the fleet number remained the same.
As the successor to the AEC Regal III, this was the first Canberra bus that could be operated without a conductor. It was also the first to include a front route-destination box.
One member of this class, number 037, which entered service in December 1960, was fitted with air bag suspension, one of the first city buses in Australia so equipped.
A further 40 of the AH470-powered buses were purchased between 1962 and 1966, including eight bodied by ComEng.
The ComEng bodied AEC Reliances were allocated the following fleet numbers: 001-014, 016-053, 066-073.