the Dx

An NZR photo of Dx 2615 in December 1975 at Marton upon its introduction - one possibly two Bedford trucks can be seen further down the platform.

The 50 members of Co-Co type DX class (the next logical alphabetical designation available at the time was DK so maybe the X stood for extra big?) were introduced on NZR between 1972 and 1976. They are based on the General Electric U26C, a narrow-gauge version of the GE U23C model, which is also used in South Africa, Brazil, Kenya, and, in modified form, in Tanzania/Zambia.

The locomotives were initially confined to the NIMT and the Marton - New Plymouth Line, due to their high axle loading, and a need for the extra power on these lines. The electrification of the central section of the North Island Main Trunk in 1988 saw DXs redistributed, including to the South Island.

Upon introduction, all the DXs were painted in "clockwork orange" livery as in the example above. Between 1977 and 1986 they were all repainted in the "fruit salad" livery - red, grey, and yellow, which most of the class wore until the end of the decade. This livery had the road numbers displayed on the sides of the locomotives in large white numbers. The first to be painted as such was DX 2612. Since then, members of the DX class have received liveries including "Cato Blue" (fruit salad with blue instead of red), "Bumble Bee" (black and yellow), "Corn Cob" (green and yellow) and KiwiRail (grey, orange, and yellow).

Only one has so far been written off, 2639 following a crash at Newmarket in March 1977, details of which are in the book Danger Ahead: NZ railway accidents in the modern era.  Two have had a thorough rebuilding, now called DXR and the rest have had various other modifications including prime mover power output upgrades and are known as DXB or DXC..