Locomotives of New Zealand - Classification Details

Classification Details

The locomotives of KiwiRail and its predecessors are divided into classes. Each class was designed to perform specific duties. A class can be as small as one individual locomotive, and the largest class to run on New Zealand rails was the DA class, which comprised 146 locomotives.

20 new DL class Chinese-built diesel electric locomotives arrived in mid 2012.

Steam locomotives (which were retired from regular service by the end of October 1971) were originally categorised with just a single letter, such as the "F class". When a new class was built as an enhancement of an old class, the old class's letter was re-used, followed by a superscript upper-case letter. For example, the 1906 A class was followed by the AA and AB classes.

Diesel-electric and electric locomotive classifications originally consisted of an upper-case D or E respectively followed by a second and sometimes a third (sub-class) letter. The second and third letters are sometimes represented as smaller-sized upper case (for example, as seen on many locomotive cab-side number plates).

Diesel and diesel-electric classes appear to have originally been classified, after the first class letter ('D' as alluded to above), by the second letter being allocated to indicate the country of manufacture (for example DA for the American EMD designs, which were also, later, built in Canada and Australia; DE for England or 'English Electric'; DJ for the Mitsubishi units from Japan). Whilst this was a reasonable starting point, such issues as the introduction of 'sister models' and sub-classing caused by rebuild and refurbishment resulted in the pragmatic, contiguous use of other class letters. For example the eight-cylinder version of the DA class became the DB class, and was later rebuilt as the DBR. When the DA class rebuilding began, the rebuilt locomotives became the DC class. Following the DJ there was a large gap in the classification continuum as NZR took a different tack and catalogued their new GE power as the DX class and then (because the original DFs had since been withdrawn) new Canadian-built EMD units took over the DF classification.

There are exceptions, and new classes were not always given the classification that alphabetically followed that of the previous class that had most recently been acquired. If an entire class had been withdrawn from service and the classification no longer in use, it was sometimes re-used; for example, two A classes exist, one from 1873 and one from 1906.