The New Zealand AM class of electric multiple unit (EMU) was constructed for the electrification of Auckland's railway network.

While the document specified only a small number of elements, it required a speed of 110 km/h for fully laden trains, a minimum design life of 35 years and the ability to climb the steep grades of the proposed City Rail Link.

One of them, Bombardier Transportation, criticised the government for initially shortlisting four companies then extending it to ten, which in their view created a lack of confidence in the tendering process.

[14] In August 2011, it was confirmed that the tender specification had been changed to 57 three-car EMUs (approximately 50% more than before) and no locomotives, reducing long-term maintenance costs.

[15] All trains would be able to use the City Rail Link, which might not have been possible for locomotive-hauled carriages as they would not have met performance and fire rating requirements.

Further information regarding the trains was also released, including artist's impressions resembling the Class 4000 DMUs for NI Railways, built by CAF.

[22][23][24] The class was designed with the City Rail Link in mind, which will extend the underground operation of the 57 units and any future suburban stock considerably.

AT looked into the possibility of battery electric multiple units (BEMU) to operate services between Papakura and Pukekohe as an interim measure prior to electrifying the North Island Main Trunk between the two stations.

[25] The rationale for this became clear in late April 2018 when electrification between Papakura and Pukekohe was announced as part of the $28 billion Auckland Transport Alignment Project.

Electric trains were fully introduced into daily services across the Auckland electrified rail network on 20 July 2015.

[40] The front three cars[41] of an inbound train derailed in the Britomart tunnel on the approach to the platforms on 9 May 2018 and stopped millimetres from a concrete wall.