British Rail Class 159

159 019 in Network SouthEast livery departing from Southampton in 1996

In the late 1980s, the locomotive-hauled stock on Network SouthEast's West of England route from London Waterloo to Salisbury, Yeovil Junction and Exeter St Davids was in urgent need of replacement. The British Rail Class 50 locomotives were not suited to the stop-start nature of the route, and frequently broke down.[9] Because of the long sections of single track west of Salisbury following the Beeching cuts, a single breakdown could cause chaos. Various options were considered including electrification, shortened HSTs, construction of new locomotives and stock (a passenger version of the proposed Class 48), or the proposed Class 171 (which would been part of the Networker family, an intercity version of the Class 165 – not to be confused with the later Turbostars). A study found the best options were electrification or new DMUs.[10]

With the UK economy in decline in the early 1990s, it was found that Regional Railways had over-ordered Class 158s at the same time as Network SouthEast was looking for a similar number of new diesel trains. NSE agreed to take on the surplus Class 158s.[10]

The original 22 units were built as Class 158 units, but were rebuilt by Babcock Rail in Rosyth Dockyard before entering traffic. This entailed fitting first-class accommodation and retention toilets, and various other modifications. The rebuild was required because it was not possible for Network SouthEast and the newly privatised BREL to agree terms on the variation order to NSE specification.[11]

The first unit (159004) was handed over to NSE on 6 January 1993.[1]

The 1992–1993-build units are numbered 159001-022, with individual cars numbered 52873-894 and 57873-894 for driving motor vehicles, and 58718-739 for intermediate motor vehicles. The entire class is maintained at a purpose-built depot at Salisbury.[3][2]

In 2007, eight further Class 159 units were created through the rebuilding of surplus Class 158 units displaced from TransPennine Express.[12]

All units use P4-4A and T4-4A bogies.

The units feature BSI couplers. This enables them to work in multiple with Class 158 and Class 170 units, as well as units of the same class.

• On 4 January 2010, Class 142 diesel multiple unit 142029 collided with a train composed of two Class 159 units at Exeter St Davids. Nine people were injured.[13]

A refurbished Class 159/0 No. 159012 at Plymouth

The units were dedicated to the West of England sector of Network South East, operating services between London Waterloo and Exeter; they also worked services between Salisbury and Southampton and on the Reading to Basingstoke line, replacing elderly DEMUs. They then transferred to the South West Trains shadow franchise in readiness for privatisation.

Upon the privatisation of British Rail, the West of England route passed in 1996 to the South West Trains franchise, which was won by the Stagecoach Group.[14] Starting in 2000, units were progressively refurbished and repainted from Network SouthEast's blue, red and white livery into South West Trains' express livery. Other post-privatisation modifications included clearer LED destination displays, upgraded air-conditioning, and more openable windows.

Currently, the Class 159s operate mainly from London Waterloo to Salisbury/Exeter in three- or six-coach formations, and between Salisbury and Exeter in three- or six-coach formations. Until the December 2009 timetable change,[15] some trains continued beyond Exeter to Paignton, Plymouth and Penzance; these usually operated as three-coach units, though at weekends there were some six-coach formations. These services are now operated by the Great Western Railway. The service to Bristol Temple Meads is now also in the hands of Class 159s.

Since 2006, the original Class 159 fleet of 22 has been supplemented by eight three-coach 158s (renumbered into the 159/1 series) and 11 two-coach Class 158s. The decision to standardise on 158s and 159s allowed the nine Class 170 'Turbostar' units to be transferred to other operators.[12] Eight went to First TransPennine Express, with the remaining unit going to Southern for integration into Class 171 Turbostars.