NIR Class 4000

Northern Ireland Railways Class 4000 "C4K"
Class 4000 train at Belfast Great Victoria Street.
Manufacturer	CAF
Family name	CxK
Entered service	2011–2012
Number under construction	20 sets (60 cars, option for 20 more cars)
Formation	3-car sets, (option for 4th car)
Capacity	216 seated
Operator(s)	NI Railways
Specifications
Maximum speed	90 mph (145 km/h)
Prime mover(s)	One MTU 6H1800R83 diesel of 530 hp (395.2 kW) per car
Transmission	ZF Ecomat-Rail 6 speed ZF Reversing final drive
Safety system(s)	AWS, TPWS
Track gauge	1,600 mm (5 ft 3 in)

The Class 4000 is a type of diesel multiple unit in service with NI Railways.

The fleet covers 20 DMUs procured by Translink. None of the Northern Irish rail network is electrified, and diesel multiple units have been used since nationalisation in the 1950s.

Prior to 2000, the NIR rolling stock consisted of a mixture of diesel multiple unit types that had entered service between 15 and 25 years previously. The main type was the Class 80, based on the Mark 2b bodyshell, 22 3-car and 4-car units built in two batches between 1973 and 1978. Additional capacity was provided with the Class 450, nine 3-car units that entered service in 1985 based on the Mark 3 bodyshell. Chronic underinvestment in the railway meant that by the millennium these were the newest domestic trains. By 2000 it was estimated that the network required investment of £183 million to bring it up to basic safety standards.

Recognising that the railways serve an important role in the growth of the local economy, the devolved Northern Ireland Assembly granted funding for improvements in December 2000 following the report of the Railways Task Force. Included was £80 million for rolling stock, the largest order in the history of NIR. The result was the Class 3000 DMU from CAF in Spain, 23 three-car units to replace the increasingly outdated Class 80. They entered service between 2004 and 2005. This was a like-for-like replacement meaning that older rolling stock had to be retained, and NIR could not introduce the service enhancements it desired.

The expanding economy led to increasing pressure to improve the rail network, with recommendations made in a debate in the Northern Ireland Assembly in May 2007. Among these was the purchase of rolling stock to replace the remaining Class 80 and Class 450 trains. Translink instituted the "New Trains 2010" (later renamed "New Trains Two") proposal for new trains, and decided that it needed to improve its service frequency to go with the associated infrastructure improvements, which would mean expanding the fleet. The proposal was that up to 20 trains would be purchased, which would replace the Class 450 and 80 units and expand the fleet by up to seven trains. The go-ahead was given on the publication of the draft budget of the Department for Regional Development, which allocated £137 million over three years to Translink, including for 20 trains.