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| Class 168 | |
|---|---|
| Name | Class 168 |
| Service | 1998–present |
| Family | Turbostar |
| Operator | Chiltern Railways |
| Formation | 3-car or 4-car sets |
| Yearconstruction | 1998–2004 |
| Maxspeed | 100 mph |
Class 168 is a British diesel multiple unit train type introduced in the late 1990s for regional and intercity services. Built as part of the Turbostar family by manufacturers associated with Adtranz, Bombardier Transportation, and later Alstom, the sets were procured for operators including Chiltern Railways and have operated on routes connecting London Marylebone, Birmingham Moor Street, Oxford, and Banbury. The design reflects developments in post-privatisation rolling stock procurement involving Railtrack, Strategic Rail Authority, and later Network Rail infrastructure contexts.
The design evolved from concepts tested in the 1990s with influences from previous stock such as the Class 165 and Class 170, aligning with procurement strategies of operators like Central Trains and First Great Western. Development involved engineering teams that had previously worked on projects for British Rail successors and leveraged manufacturing facilities in Derby and components from suppliers with contracts under Railtrack era specifications. Key stakeholders included franchising authorities during the Privatisation of British Rail and major rolling-stock leasing companies such as Angel Trains and Porterbrook. The external styling and structural layout were influenced by crashworthiness standards promulgated after inquiries such as the Railway Safety Regulations revisions and by industry bodies including RSSB.
Units were built with aluminium alloy bodies over steel underframes, employing bogies related to those used on other Turbostar family members. Propulsion is provided by turbocharged diesel engines meeting emissions guidance in force at delivery, coupled to hydraulic transmissions and multiple-unit control compatible with TOPS classifications. Maximum speed is 100 mph, braking systems combine air brakes with dynamic retardation, and passenger doors use electric sliding mechanisms interfacing with platform detection systems at stations like Leamington Spa and High Wycombe. Onboard systems integrate passenger information displays, vehicle-trainlink communications compatible with lineside signalling governed by AWS and TPWS installations overseen by Network Rail.
The fleet was delivered in multiple configurations reflecting operator requirements and leasing arrangements. Early batches shared components with the Class 165 family while later batches incorporated refinements comparable to the Class 170 and subsequent Turbostar derivatives. Variants differ by formation length, interior specification commissioned by Chiltern Railways or former franchises, and by traction equipment tuned for services on the Northolt Line and the Cherwell Valley Line. Some units were modified to operate in push-pull formations with driving trailers compatible with depots such as Tyseley Depot.
Primary operation has been on services radiating from London Marylebone, serving regional centres including Birmingham Snow Hill, Oxford, Wolverhampton, and commuter markets to Leamington Spa. Deployment was shaped by timetable changes negotiated between franchise holders and the Department for Transport, and by infrastructure upgrades like the Bicester chord and resignalling projects at Banbury. Units have been maintained at facilities under contracts with ROSCOs and operators, and have been sub-leased or cascaded in response to rolling stock cascades involving fleets such as the Class 172 and Class 168-family neighbours.
Passenger accommodation was specified for regional and semi-fast services, with features such as high-backed seating, luggage racks for routes serving Heathrow Airport connections, and passenger information systems for stations including High Wycombe and Princes Risborough. Accessibility improvements were progressively introduced to comply with standards influenced by legislation like the Disability Discrimination Act and guidance from bodies such as the Office of Rail and Road. Onboard comfort systems include HVAC units and retention toilets meeting depot servicing regimes at locations such as Aylesbury.
Over their service life, sets underwent interior refurbishments commissioned by operators including Chiltern Railways to provide refreshed seating, LED passenger information displays, and improved CCTV supplied by firms contracted under national procurement frameworks. Modifications addressed reliability improvements in traction control and HVAC systems, and some units received liveries updated to align with franchise branding agreements governed by the Department for Transport franchise specifications. Upgrades to meet evolving safety mandates involved retrofitting of modern train protection equipment and enhancements tied to Rail Accident Investigation Branch recommendations following incidents across the network.
Individual units have been involved in service incidents reported in the context of national investigations by the Rail Accident Investigation Branch and safety oversight by the Office of Rail and Road. Notable occurrences prompted recommendations on operating procedures at junctions such as those near Banbury and signalling reviews at interlockings serving Birmingham Moor Street. Investigations led to technical and operational changes implemented across regional fleets, with lessons shared in industry forums including meetings of the RSSB.
Category:British diesel multiple units