NZR DA Class - in Service

In Service

The class operated predominantly in the North Island, with only limited service in the South Island for many years. They were employed mainly on the major lines in the North Island – the NIMT, Marton-New Plymouth, Palmerston North-Gisborne and North Auckland lines – where they displaced the steam locomotives that had dominated NZR operation until that time.

The class did face some operating restrictions. They were excluded from operating on many branch lines on account of their weight, and were restricted in their operations on the East Coast Main Trunk beyond Paeroa due to the line through the Karangahake and Athenree gorges with NZR using the lighter Df and Db class to handle traffic on this line. These restrictions were reduced as bridges were progressively strengthened, and in the case of the ECMT the opening of the Kaimai Tunnel in 1978.

The class were also unable initially to access Wellington via the NIMT, as the tunnels south of Paekakariki built in the 1880s by the WMR were not large enough for them. The operational practice remained the same as it had in the steam age with an exchange with ED and EW electric locomotives taking place at Paekakariki, until the tunnel floors were lowered in 1967 and they could operate through to Wellington. Access to Wellington before this time could only be achieved via the Wairarapa line and the Rimutaka Tunnel.

The class hauled all manner of freight and passenger services, including the “Scenic Daylight” service on the NIMT. The prestigious "Silver Star" overnight sleeper train was initially hauled by a pair of Da locomotives when it was introduced in 1971. A dedicated pool of locomotives - Da's 1520-1527 and later joined by 1528 - were used for this service.

However the need for a more powerful locomotive that could haul longer and heavier trains on the NIMT had been identified and in 1972 the first 15 Dx class locomotives were introduced. While a single Dx produced 70 kW less than a pair of Da’s, it weighed 97.5 tonnes compared to the combined Da’s 162 tonnes, which combined with more powered axles gave better traction and higher power to weight.

The Silver Star service was later transferred to the Dx’s, while the Scenic Daylight service had earlier been replaced by the “Blue Streak” railcars. The introduction of further Dx class locomotives in 1975-76 effectively removed the Da’s from NIMT service.

Units were also employed on the Auckland suburban network, hauling 56-foot carriages. These services terminated at the Auckland Railway Station, forerunning the services run by many of the DC class today.

Those locomotives that were not converted to the DC class continued in service throughout most of the 1980s. However the combination, the deregulation of land transport and decline in rail freight volumes, reduced inter-regional passenger numbers, and the electrification of the NIMT saw them become surplus to requirements.