NIR Class 450

Northern Ireland Railways Class 450
8459 passing the site of Barn Halt.
In service	1985-2012
Manufacturer	BREL
Family name	BR Second Generation (Mark 3)
Entered service	1985–1987
Number built	9 sets
Number scrapped	8 sets
Formation	3-car sets (DM-T-DT)
Fleet numbers	Originally: 451–459, Now: 8451–8459
Capacity	184 seats
Operator(s)	Northern Ireland Railways
Line(s) served	At time of withdrawal: Belfast-Larne Coleraine-Portrush Formerly: Belfast-Bangor Belfast-Newry
Specifications
Maximum speed	75 mph (121 km/h)
Prime mover(s)	English Electric 4SRKT
Safety system(s)	AWS, TPWS
Track gauge	1,600 mm (5 ft 3 in)

The Class 450 is a type of diesel multiple unit (DMU) formerly used by Northern Ireland Railways. They were affectionately nicknamed 'Thumpers' and 'Castles' (Also known as the Castle Class) by rail enthusiasts.

In the mid 1980s, Northern Ireland Railways was in the process of upgrading its rolling stock. Having already purchased three new locomotives, it then proceeded to purchase replacements for its Class 70 diesel multiple units. A total of nine three car trains were constructed by BREL between 1985 and 1987 intended to supplement the existing Class 80 DMUs then in service. The trains were constructed using underframes of existing Mark 1 coaching stock, altered to 1,600 mm (5 ft 3 in) and new Mark 3 bodyshells. Because of this, they bear a strong resemblance to the British Rail Class 150, British Rail Class 210 (based on), British Rail Class 317, British Rail Class 318 and British Rail Class 455, as they use Mark 3 bodyshells. These were combined with refurbished power units and traction motors from the withdrawn Class 70 units (there were only eight Class 70 units available to be salvaged, so the equipment for the ninth train came from a withdrawn Class 80 train, powercar 88).

The power cars of the Class 450 units are named after various Northern Irish castles. They entered service in a cream, orange, and red livery.

On 9 March 1995, a 450 Class train was used to form a royal train when Queen Elizabeth II officially opened the Dargan Bridge, composed of two cars from 455 coupled to two cars from 459.

The Class 450 operate on the same principle as the prototype Class 210 DMUs on the British network, in that they consist of a single power car containing the traction and generating equipment (numbered 45x), an intermediate trailer car (numbered 79x) and a driving trailer (numbered 78x) as permanently formed 3 car sets. An additional "8" was added to the start of all the cars so that they can be used by Translink's computer system.