The NZR

New Zealand Railways Department

The New Zealand Railways Department, NZR or NZGR and often known as the "Railways", was a government department charged with owning and maintaining New Zealand's railway infrastructure and operating the railway system. The Department was created in 1880 and was reformed in 1981 into the New...

 DX class is a class of 49 Co-Co diesel-electric locomotives

Diesel locomotive

A diesel locomotive is a type of railroad locomotive in which the prime mover is a diesel engine, a reciprocating engine operating on the Diesel cycle as invented by Dr. Rudolf Diesel...

 that currently operates on New Zealand

New Zealand

New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

's national railway network

Rail transport in New Zealand

Rail transport in New Zealand consists of a network of gauge railway lines in both the North and South Islands. Rail services are focused primarily on freight, particularly bulk freight, with limited passenger services on some lines...

.

Built by General Electric

GE Transportation Systems

GE Transportation, formerly known as GE Rail, is a division of General Electric. The organization manufactures equipment for the railroad, marine, mining, drilling and energy generation industries. It is based in Erie, Pennsylvania. Locomotives are assembled at the Erie plant, while engine...

 in Erie

Erie, Pennsylvania

Erie is a city located in northwestern Pennsylvania in the United States. Named for the lake and the Native American tribe that resided along its southern shore, Erie is the state's fourth-largest city , with a population of 102,000...

, Pennsylvania

Pennsylvania

The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...

, United States

United States

The United States of America is a federal constitutional republic comprising fifty states and a federal district...

, they were introduced to New Zealand between 1972 and 1976. The class is based on the General Electric U26C model

GE U26C

The GE U26C diesel locomotive model was introduced by GE Transportation Systems in 1971. All examples of this model are six axle units, and have the wheel arrangement C-C or Co'Co' ....

, a narrow-gauge version of the GE U23C

GE U23C

The 2300 horsepower GE U23C diesel locomotive model was first offered by GE in 1968, and featured a V-type 12 cylinder version of the standard GE FDL diesel motor. Designed as a competitor to EMD's SD38 and SD39 series, it was intended for heavy transfer, drag and hump service where speed was not...

 model. The U26C is also used in South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

 (see South African Class 34-900

South African Class 34-900

Between October 1979 and February 1981 the South African Railways placed thirty Class 34-900 GE U26C diesel-electric locomotives in service.-Manufacturer:...

), Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

, Kenya

Kenya

Kenya , officially known as the Republic of Kenya, is a country in East Africa that lies on the equator, with the Indian Ocean to its south-east...

, and, in modified form, in Tanzania

Tanzania

The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...

/Zambia

Zambia

Zambia , officially the Republic of Zambia, is a landlocked country in Southern Africa. The neighbouring countries are the Democratic Republic of the Congo to the north, Tanzania to the north-east, Malawi to the east, Mozambique, Zimbabwe, Botswana and Namibia to the south, and Angola to the west....

.

The locomotives were initially confined to the North Island Main Trunk and Marton - New Plymouth Line, due to their high axle loading, and the need for the extra power of the DX on these lines.