See also: Rail transport in Ireland
NI Railways, also known as Northern Ireland Railways (NIR) and for a brief period Ulster Transport Railways (UTR), is the railway operator in Northern Ireland. NIR is a subsidiary of Translink, whose parent company is the Northern Ireland Transport Holding Company (NITHCo), and is one of two state-owned train operators in the United Kingdom, the other being Eurostar. It has a common Board of Management with the other two companies in the group, Ulsterbus and Metro (formerly Citybus).
The rail network in Northern Ireland is not part of the National Rail network of Great Britain, being part of the Irish Gauge network covering the island of Ireland. Also, NIR is the only commercial non-heritage passenger operator in the United Kingdom to operate a vertical integration model, with responsibility of all aspects of the network including running trains, maintaining rolling stock and infrastructure, and pricing.
NIR jointly runs the Enterprise train service between Belfast and Dublin with Iarnród Éireann. There is no link to the rail system in Great Britain, although proposals have been made, though allowances would have to be made for the different rail gauge (standard gauge) in use in Britain and the rest of Europe.
NIR was formed in 1968 when it took over from the Ulster Transport Authority (UTA), which had operated the province's railways since 1948. Much of the network closed during the 1950s and 1960s, declining from 900 miles (1,500 km) to 206.61 miles (330.58 km) at present.
Suffering frequent disruption and damage to infrastructure caused by the Troubles and starved of investment by successive political administrations, the NIR network had become badly run down by the 1960s, with old rolling stock and poorly maintained track. NIR's last steam locomotives were withdrawn in 1970.
In 1970, NIR re-launched the once-popular Enterprise between Dublin and Belfast with three new NIR Class 101 diesel locomotives built by Hunslet in England and Mark 2B carriages built by BREL. Despite frequent interruptions due to bomb scares, the service has remained a more or less constant feature of the NIR network.
As older trains became obsolete in the 1970s, the Class 80 slam-door diesel-electric multiple unit was introduced. BREL built these units between 1974 and 1977 to British Rail's Mk 2B design with some trailer cars rebuilt from hauled stock. The power cars are powered by an English Electric 4SRKT engine, nicknamed 'Thumpers' due to their characteristic sound, and have two English Electric 538 traction motors. These entered service on the suburban lines around Belfast, becoming a stalwart on the whole network. They remained in service until 2012, latterly primarily on the Larne-Belfast line and the Coleraine-Portrush Line. In the early 1980s, NIR purchased one of the prototype LEV Railbuses built to test the railbus concept. This was intended for the Coleraine-Portrush branch, but was withdrawn due to the capacity constraints of a single car. A plan was mooted to utilise it on the Lisburn-Antrim line to prevent it from being closed. This proposal failed, again because of the limited capacity.
During the eighties it was apparent that additional trains would be needed. BREL built nine 450 Class sets on former Mk 1 underframes between 1985 and 1987. The power cars had an English Electric 4SRKT engine recovered from former 70 Class units (except 457, which uses the engine recovered from 80 Class power car 88) and had two English Electric 538 traction motors. The sets were three-car diesel-electric multiple units, based on a more modern British design, with air-operated sliding doors. They were withdrawn from service in 2012 and replaced by new 4000 class diesel multiple units..
In 2004/2005, NIR received 23 3000 class diesel multiple units from CAF of Spain in an £80m order. The final unit, 3023, arrived in Belfast Harbour on 18 July 2005. All units had entered service by 24 September 2005. They operate principally between Bangor, Portadown and Londonderry and Belfast. In 2010-12 additional CAF-built diesel multiple units of the 4000 class were introduced.