The NZR class A^B was a class of 141 superheated two-cylinder Pacifics. Its origins can be traced back to the class A of 1906 that was a saturated four-cylinder compound. No. 409 of this class was built as a simple two-cylinder and in 1915, production of the superheated class A^B started. By 1927, 38 had been built in the NZR Addington Workshops, 83 by North British and 20 by A & G Price. The locomotives from North British differed from the rest in a firebox area of 124 instead of 115 square feet and a superheater that was only 155 instead of 204 square feet.

A feature of these locomotives was the Vanderbilt tender. They were the largest class of NZR steam locomotives and were used in passenger and freight service. On relatively flat lines, they could handle 350-ton express trains at 60 mph or 97 km/h and were able to haul freight trains of 750 tons. Some claim that they were the first steam locomotives to reach a power of 1 hp for every 100 pounds of empty weight. As loco-info's power estimation leads to 0.0096 hp per pound of service weight, this claim might actually be true.

The superheated standard boiler of the A^B was later also fitted to locomotives of the classes Q and A^A. The class W^AB was a 4-6-4T tank locomotive that was built in parallel to the A^B with the same boiler. Between 1947 and 1957, eleven of these were rebuilt to the A^B.

The most time of their career, they were used on the North Island. When diesel locomotives arrived there around 1955, they came to the South Island. In the late fifties and early sixties, some were withdrawn and others with damaged frames got the frames from these withdrawn locomotives. They spent their last years on branch lines and between 1963 and 1967, the largest number was withdrawn. The last ones survived until the end of steam in 1971. Today seven are preserved, with three currently operational.

When the trains became heavier and heavier, the NZR developed a powerful shunting locomotive as a tender locomotive. In order to keep the axle load low and to enable sufficiently large driving wheels for occasional use in front of passenger trains, the class W^F 2-6-4T tank locomotive was used as the basis and the second trailing axle was removed. After the class C had become too light for the ever heavier trains, it was also used for suburban trains. Half of the locomotives were retired between 1964 and 1968.

The only Garratt locomotives to ever operate in New Zealand were the three members of the class G delivered in 1928. They had been ordered due to rising train loads on the heavy grades on the North Island Main Trunk. By introducing such powerful locomotives, it was hoped to dispense with banking altogether.

They were designed as Double Pacifics and a special feature that distinguished them from other Garratts was the coal bunker that was located on an extension of the main frame behind the cab. This bunker was connected to a mechanical stoker. They also belonged to the few Garratts with three cylinders per bogie. While the outside cylinders were operated by Walschaerts valve gear, the inside ones were operated by these through a Gresley-Holcroft mechanism.

When it became obvious that these locomotives were too large and complicated for the requirements in New Zealand, it was decided to rebuild them into six Pacifics. The rebuilds were finished in 1937 and 1938 and featured a new centre cylinder to fit the smokebox that was now located above the cylinder. They came to the south island and were withdrawn in 1956.

After some British locomotives, the K class of 1877 was the first US locomotive to see service in New Zealand. Externally, compared to the British locomotives, it had many special features that caused a stir. These included the graceful bar frame, the swiveling trailing axle, many attachments located outside of the boiler and the rich decoration. The agile running characteristics in particular were apparently an advantage over the predecessors on the South Island of New Zealand. With the introduction of more powerful locomotives, they were used more on branch lines and some were moved to the North Island. After receiving new boilers, some with Belpaire fireboxes, they were retired in the 1920s.

Since the three Class G Garratts procured in 1928 could not convince due to various problems, a new, powerful locomotive for heavy passenger and freight trains was needed for the mountainous North Island Main Trunk Railway. In order to be able to avoid further problems with articulated locomotives, a heavy locomotive with a 4-8-2 wheel arrangement was initially planned. A major problem with the limited loading gauge of the Cape gauge lines was getting the most powerful locomotive possible to operate under these conditions. The locomotives were designated class K after the previous class of the same designation, supplied from the USA in 1877, was phased out towards the end of the 1920's.

The design that was finally implemented had a boiler of the maximum practicable diameter. The trailing axle was replaced with a bogie so that a large firebox could also be carried. In order to be able to arrange the largest possible cylinders within the loading gauge, they were designed with a diameter of just 20 inches and a long stroke of 26 inches. The Heusinger valve gear initially caused problems due to the excessively long piston travel, but these could be remedied by reducing the travel from eight to 7.25 inches.

The total number of 30 locomotives mainly replaced the 4-8-2 Class X locomotives. They performed very well with heavy trains and were mostly converted to oil firing after the Second World War due to the lack of coal. The changes made were carried out in parallel with their successors of the K^A class. Since there were frequent frame fractures in the area of the firebox in the K class, new frames of the same design as in the K^A were installed.

Although the switch to diesel traction took place in the mid-fifties, several examples of the class were still being overhauled at that time. All locomotives were finally decommissioned between 1964 and 1967. A total of three examples were preserved, two of which were last used as stationary steam generators. One of these two locomotives, as well as one that was recently exhibited in a museum, were selected for a renewed refurbishment in 2013 and 2014 respectively.

Double Fairlies were used on the winding and steep lines in New Zealand as early as 1872. From 1878 Avonside also manufactured Single Fairlies, which were easier to maintain with a single, larger boiler and a single driving bogie. These were the 18 members of class R and the seven members of the heavier class S.

The class R was able to prove that it was technically capable of reaching a speed of 53 mph or 85 km/h. However, due to the laterally movable bogie, the running smoothness was very poor. However, since the speeds were generally significantly lower, the locomotives could be used successfully. They later received larger water tanks and a new boiler with higher pressure.

The retirements of the class R took place between 1919 and 1944. Three machines were handed over by the NZR to the Sanson Tramway. R 28 was used for shunting in the port of Timaru until 1940. Today she is the only surviving R and only Single Fairlie in New Zealand and is located in Reefton. She was actually planned to be made operational again by 2018, but there is currently nothing further to read about the progress.