British Rail Class 115

British Rail Class 115
A Class 115 at Marylebone in April 1981.
In service	1960–1998
Manufacturer	BR Derby
Number built	41 four-car sets
Formation	DMBS–TCL–TS–DMBS
Capacity	DMBS: 78 Second; TCL 30 First, 40 Second; TS: 106 Second; 4-car total: 30 First, 302 Second
Operator(s)	British Rail
Line(s) served	Chiltern Main Line, London to Aylesbury Line
Specifications
Car length	63 ft 6 in (19.35 m)
Width	9 ft 3 in (2.82 m)
Maximum speed	70 mph (110 km/h)
Weight	135 long tons (137 t; 151 short tons) trainset
Prime mover(s)	Two 230 hp (172 kW) BUT (Leyland Albion) per DMBS
Power output	920 hp (686 kW) per set
Auxiliaries	Albion
Safety system(s)	AWS
Multiple working	■ Blue Square
Track gauge	4 ft 8 1⁄2 in (1,435 mm)

The British Rail Class 115 diesel multiple units were 41 high density sets which operated the outer-suburban services from Marylebone usually to destinations such as High Wycombe, Aylesbury and Banbury which are on the Chiltern Main Line and Great Central Main Line (now the London to Aylesbury Line). Sometimes, these sets used to operate 8-12 car long expresses to Nottingham Victoria in the final years of the GCML. Coincidentally, Class 115 units operated services under Table 115 in the British Rail timetable.

Based on the basic Derby high density design, the sets are similar to Class 127 but were internally superior as the class had larger windows, better furnishings, lighting and wall surfaces.

Some sets were also built for the CLC line between Liverpool and Manchester. These were later transferred to Marylebone. They also worked from Tyseley in the later years.

The Marylebone sets, which were later transferred to Bletchley but remained on Chiltern Line duties (and finally to Old Oak Common), were declared surplus after the introduction of Class 165s, from 1991 onwards. While at Bletchley and Old Oak Common depots the class found use on the Gospel Oak to Barking Line, units being formed as power twins. They were, in turn, replaced on this line by Class 117 power twins, displaced from Paddington suburban duties.