The D^F was the first class of diesel locomotives that the NZR procured for use on main lines. The engine used was the well-known turbo diesel from English Electric with twelve cylinders and an output of 1,500 hp. In order to be able to maintain an axle load of twelve long tons, the weight had to be distributed over ten axles. Thus there were a total of six powered axles in two bogies and one two-axle bogie at each end.

Originally 31 machines were ordered, but the order was subsequently reduced to ten. Instead of the remaining 21 D^F, 42 smaller D^G were ordered, which compared to the D^F had half the power and only one driver's cab. The ten locomotives were only used on the North Island and mostly in front of freight trains. They were mainly to be found on routes for which the slightly less powerful class D^A had too high an axle load. In 1964 they were renumbered from 1500 to 1509 to the new number range between 1300 and 1309. In the Seventies a transfer to the South Island was planned, but this did not take place due to the lighter class D^J.

Thus, all locomotives were retired between 1972 and 1975. A few years later, the class D^F was assigned to a new locomotive from General Motors Diesel. Today only the 1301 is preserved, which now carries the old number 1501 again. It stood outdoors for a long time and was soon in a corresponding state. In 2008 it was taken over by the Diesel Traction Group and is being restored since 2018.

The first numerically larger class of diesel locomotives in New Zealand to replace significant numbers of steam locomotives was the D^A class. It was based on the EMD G12 in the version with four driven axles. The loading gauge had been adjusted for the cape gauge routes in New Zealand. The class was initially named D^A, later the spelling was changed to DA. General Motors Diesel in Canada was awarded the contract after first delivery was promised within five months.

Production of the first 30 examples was split between GMD's plant in London, Ontario and EMD's plant in La Grange, Illinois. Together with the ten engines built by Clyde Engineering in Australia in 1957 these were referred to as Phase I. In 1961, a further twelve were delivered by GMD, forming Phase II. The largest number of units was phase III, of which 40 examples were built between 1962 and 1964 and 54 examples in 1966 and 1967.

Despite the modified loading gauge, the locomotives could not be used on many routes in the early days because they were still too big or too heavy. Only over time the cross-section of tunnels was enlarged and bridges strengthened. Another limitation were the welded bogies on Phase I locos, which did not perform well in curves and prevented the use on passenger trains. Only the locomotives from phase II onwards had new bogies with a cast frame and revised suspension, which could also be used for passenger and express trains.

DC No. 4939 and 4916 in February 2015 in Helensville

GPS 56 / https://www.flickr.com/people/91807507@N03

In 1970, six engines were equipped with slow-speed control for shunting, creating the D^AA class. From 1972 the D^A class locomotives were increasingly replaced by the new D^X class locomotives. Between 1978 and 1981, 85 Phase II and III examples were converted by Clyde Engineering to the new Class DC, bringing them to the EMD G22AR specifications. In addition to a 645 series prime mover, they received new cabs which, thanks to the dynamic brake ventilation grilles being moved to the rear, now had a low short hood for better visibility.

The unconverted locomotives were retired by 1989. Number 512 was sold to Tasmania and converted to the DAR class with a new Caterpillar D343T engine. The converted locomotives only came to the South Island after the deregulation of freight traffic. After the turn of the millennium there were problems with corrosion on the cab, leading to the possibility of the cab detaching from the frame in case of an accident, endangering the life of the driver. This meant that the locomotives could only be used behind another locomotive.

Some engines later made their way to Tasmania and Queensland and two were sold to Namibia in 2021. In July 2021, 67 of the 85 class DA vehicles had already disappeared from the roster. The last ones will probably not have a long life either, since they will be replaced by the DL class locos built by CRRC in China.

From 2002 there were plans in New Zealand at KiwiRail to procure new diesel locomotives. After realizing that New Zealand did not have the necessary know-how for completely independent production and that the American and Australian manufacturers could not deliver in a timely manner, they were the first western railway company to order locomotives in China. They came from CRRC Dalian and were powered by a 20-cylinder diesel from the German manufacturer MTU. With an output of 3,600 hp, they are the most powerful diesel-electric locomotives in New Zealand. Although there were initially problems with the reliability, these were resolved and a total of 73 locomotives were built from five orders between 2009 and 2023.