The British Rail Class 156 Super Sprinter is a diesel multiple unit passenger train. A total of 114 sets were built between 1987 and 1989 for British Rail by Metro-Cammell's Washwood Heath works. They were built to replace elderly first-generation DMUs and locomotive-hauled passenger trains. Background By the beginning of the 1980s, British Rail (BR) operated a large fleet of first generation DMUs, which had been constructed in prior decades to various designs. While formulating its long-term strategy for this sector of its operations, British Rail planners recognised that there would be considerable costs incurred by undertaking refurbishment programmes necessary for the continued use of these ageing multiple units. Planners instead examined the prospects for the development and introduction of a new generation of DMUs to succeed the first generation. The initial specification was relatively ambitious, calling for a maximum speed of and acceleration comparable to contemporary EMUs. This specification led to the experimental British Rail Class 210 DMU. However, it was found to be expensive, and it was recognised that a production model assembled from proven components would possess greater reliability and lower maintenance costs; an availability rate of 85 percent was forecast. By 1983, experiences with the Class 210 had influenced BR planners to favour procuring a new generation of DMUs, but to also adopt a new specification that were somewhat less demanding than before. Specifically, it was decided to drop the top speed from , as testing had revealed the higher rate to deliver no perceivable improvement in journey times due to the typically short spacing of the stations the type was intended to serve. The requests for compatibility with other rolling stock were eliminated, although auto-coupling and auto-connecting functionality was added. In addition to a good ride quality, the specification included a sound level of 90 dB when at full speed, an operational range of , and an interval between major overhauls of five years or . The bid submitted by British Rail Engineering Limited (BREL) was heavily based on its successful Class 455 EMU, sharing its body and the majority of its running gear, albeit equipped with two different power trains. The resulting Class 150 was viewed as unsatisfactory for more-upmarket services. Studies showed coaches could be stretched, providing more internal volume and thus enabling the somewhat cramped two-by-three seating arrangement of the Class 150 to be substituted with a more roomy two-by-two counterpart. These