Rail traffic in New Zealand is mainly handled by Kiwi Rail. Train traffic consists mainly of cargo trains. Some touristic oriented passenger services do exist, such as the trains named TranzAlpine, Coastal Pacific and Northern Explorer. In addition to Kiwi Rail there are also some other operators, such as the small operator called The Dunedin Railways, which handles local and touristic traffic around Dunedin on the South Island of New Zealand. There are also other operators such as the Transdev group, which operates in a number of countries globally. New Zealand has 4128 km of railroad lines out of which over 2300 km are for cargo trains only. About 600 km are electrified. The track gauge used is the so called Cape gauge 1067 mm and the electric system used is 25 kV AC. The administration of New Zealand's rail systems has gone back and forth between a totally nationalised system (Total goverment control 1876-1982), corporatised and private systems and is currently moving again towards renewed nationalisation.

Here we see Kiwi Rail diesel locomotive DC4058 ready to start pulling the "Northern Explorer" passenger train towards Wellington. This picture is from 2014. The line towards Wellington was electrified, but nevertheless high ranking passenger trains were being pulled by diesels. In 2016 a decision was made to totally get rid of electric traction on main lines, but that decision was reverted in 2018. Now the current plan is to revamp old electric locomotives and scrap these class DC and DCP diesel machines.
Picture from Hamilton Frankton station 19.4.2014 by Johannes Erra.

DXB 5143 stands at Wellington Railway Station platform 9 on 1st July 2008. DXB 5143 was the first locomotive to be painted in the KiwiRail livery, and was used for the official launch of KiwiRail by Prime Minister Helen Clark that day.
The locomotive is one of the DX series machines built by General Electric in USA 1972-75. This variant DXR weigs 105 tons. It has a General Electric 7FDL-12 V12 diesel engine providing a power rating of 2240 kW and a maximum speed of 105 km/h. Their nickname is Dixie. Picture by Wikipedia user "Palmeriain" 1.7.2008. Published under the Creative Commons licence CC BY-SA 3.0.

These old passenger coaches are originally from British Rail and they are of BR's type Mk.2. Some Mk.2 coaches were sold used to New Zealand where they got Cape gauge 1067 mm bogies and new paintings.
Picture from Palmerston North 19.4.2014 by Johannes Erra.