The first batch was classified 168/0 underTOPS and resembled theClass 165 units previously built byBREL York. The Networker-design cab was an interim solution pending the design of a completely new cab for further Turbostar batches. Subsequent builds, subclassed as 168/1 and 168/2, were constructed at the same time as theClass 170 Turbostar and thus are part of theTurbostar family of trains.
Network SouthEast originally planned the Class 168 for its expansion of service on theChiltern Main Line toBirmingham Snow Hill orNew Street. These units were planned to have a higher top speed of 100 mph (160 km/h) and better acceleration than the Class 165 Networker Turbo DMU trains. In the event, privatisation intervened before Network SouthEast acquired any trains.[16]
In 2023, Chiltern announced the refurbishment of the entire class 168 fleet, costing £10.7 million. The units are receiving new carpets, reupholstered seats, 5G Wi-Fi & charging points, as well as a new revised livery.[17] The first unit to be refurbished was unveiled on 10 October 2024.[18]
Three different variants of the 168 were produced - 168/0, 168/1 and 168/2. Both Classes 168/1 and 168/2 are actually of the same design as theClass 170 Turbostar DMU trains, mainly due to the redesigned cab ends. The nine Class 170s that Chiltern obtained fromFirst TransPennine Express were converted byBrush Traction to operate with the Class 168 fleet, and redesignated as Class 168/3.[19] 168329 has been converted by Porterbrook into adiesel/battery hybrid. It was tested in 2021 on theEcclesbourne Valley Railway[20] and entered service as "HybridFlex" in February 2022.[21] it was reverted back to a regular diesel unit later that year after failed operations.[22]
^"Turbo Star" Class 168: Chiltern Railways Diesel Railcars with Voith T 211 rzze Turbo Transmission (07/2000 ed.). Heidenheim: Voith Turbo GmbH & Co. KG. G 1520 e.
^"Hybrid Powerpacks for Railcars".Rail Solution Guide(PDF) (01/22 ed.). Friedrichshafen: Rolls-Royce Power Systems AG. 26 August 2022. p. 13.Archived(PDF) from the original on 14 December 2022. Retrieved14 December 2022.
"First post-privatisation new train enters service on Chiltern Lines".RAIL. No. 332. EMAP Apex Publications. 16 June 1998. p. 11.ISSN0953-4563.OCLC49953699.