The first of the Turbostars delivered were the Class 168/0, brought into service in 1997. Adtranz (later Bombardier) of Derby produced these high quality trains for middle-distance services, but their 1/3 2/3 doors make them equally useful for commuter services. Class 168 is subdivided into /0 (the first batch), /1 (The Class 170 design) and /2 (fitted with a databus system). The /1 is classed as a 168 due to coupling compatibility, which matches the 16X series rather than 17X. This can easily be changed if required by a wiring modification; the mechanical coupling head is the same. The fleet has grown steadily with traffic requirements, hence the detail differences between them, but all are compatible and provide the same high quality interior environment.