The British Rail Class 158 Express Sprinter is a diesel multiple-unit (or DMU), built specifically for British Rail between 1989 and 1992 by BREL at its Derby Works They were built to replace many locomotive-hauled passenger trains, and allowed cascading of existing Sprinter units to replace elderly 'heritage' DMUs. The Class 159 DMUs are almost identical to the Class 158s, having been converted from Class 158 to Class 159 in two batches.
A total of 182 units were built. The majority were built as two-car sets. 17 units were built as three-car units; eight of these units have since had the centre car transferred to different units of the class, whilst another eight have been upgraded to be Class 159s The final ten units were built specifically for West Yorkshire PTE Metro services around Leeds
There were three varieties of unit when built. The standard batch, two- and three-car units (158701—158814 and 158901—158910) had 350 hp (260 kW) Cummins engines. The next batch (158815—158862) were built as non-standard to enable 350 hp (260 kW) Perkins engines to be fitted. The final batch (158863—158872) were given higher-powered Cummins engines of 400 hp (300 kW), as it was originally intended that these units would work the steeply graded Welsh Marches Line Another 22 of these higher-powered units were built, and became three-car Class 159s. Over time, the units have become mixed up as franchises changed, and higher- and lower-powered units can be seen working on the same routes. All units use P4-4A and T4-4A bogies.
