The British Rail Class 170 Turbostar is a British diesel multiple unit (DMU) passenger train built by Adtranz and later Bombardier Transportation at Derby Litchurch Lane Works. Introduced after privatisation, these trains operate regional as well as long-distance services, and to a lesser extent suburban services. A total of 139 units were built, but some were later converted to and units. These trains are currently in use with West Midlands Trains (formerly London Midland), CrossCountry, East Midlands Railway, Transport for Wales Rail, ScotRail and Northern Trains. Design The class is a development of the design used in the British Rail Class 165 and 166 DMUs known as the Networker Turbos and built by British Rail Engineering Limited and later ABB Transportation Ltd before that company became part of Bombardier. Notable features shared are the aluminium alloy frame and Voith transmission as well as the general body shape (the cab ends are similar to those of the Class 168, but not Class 165/166), interior design and door fittings. The final drive is sourced from ZF instead of Gmeinder and the diesel-engine supplier is MTU. The engine and transmission are located under the body. One bogie per coach is powered. All coaches in the set are powered when in use (there are no unpowered trailers). The units can work in multiple with trains in the 15X series, i.e. Sprinters and 14X Pacers (the latter empty only), and with other units of the same class. They are unable to operate in multiple with units in the 16X series due to different wiring arrangements. Seating arrangements are of both 2+1 (first class) and 2+2 (standard class) formation, and give a seated passenger capacity of between ~100 and ~200 per three-car set (depending on the specifications of the operator). 2-car sets are also operated. Subclasses Class 170 units have been categorised into six (originally seven) sub-classes; the basic specifications remain the same (engine, length, transmission, etc.), the differences being the seating arrangements specified by the different operators. Because of the different interior fittings the sub-classes differ in weight from one another by a small amount, up to around 2tonnes. All the sub-classes were built at Derby works either under Adtranz or Bombardier Transportation ownership. The change of ownership occurred in 2001, but early Bombardier units (such as the 2002 two-car 170/2 Phase 2 units) still display ADtranz branding, such as on the window glazing, due