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The British Rail Class 168, also known as the Chiltern Turbostar, is a diesel multiple-unit passenger train.
Fleet Background and Operational History
According to railway fleet records from Modern Railways, the British Rail Class 168 was introduced to the United Kingdom rail network starting in the late 1990s to modernize Chiltern Railways’ rolling stock. Designed as part of the Bombardier Turbostar family—one of the most successful post-privatization diesel multiple-unit designs in the UK—the trains were ordered to replace older locomotive-hauled Mark 2 coaching stock and aging diesel multiple units.
Chiltern Railways introduced the first batch of Class 168 units in 1998. Over subsequent decades, the fleet expanded through additional manufacturing batches and transfers from other operators, including former TransPennine Express equipment, to accommodate growing passenger numbers along the London-to-Birmingham corridor. Today, the fleet comprises multiple sub-classes—including the Class 168/0, Class 168/1, and Class 168/2—each featuring minor variations in interior configuration, seating capacity, and technical specifications.
Technical Specifications and Performance
The British Rail Class 168 units are powered by underfloor diesel engines supplied by Cummins, paired with hydraulic or mechanical transmissions depending on the specific sub-class. According to rolling stock data published by Rail Business Daily, the trains are cleared for a maximum operating speed of 100 miles per hour (160 km/h), making them well-suited for high-speed inter-urban running on the Chiltern Main Line.
Key technical features of the Class 168 fleet include:
- Configuration: Formed primarily as 2-car, 3-car, or 4-car formations, with gangway connections allowing passenger movement between units during multi-unit operation.
- Passenger Amenities: Equipped with air conditioning, power sockets at seats, onboard Wi-Fi, and designated bicycle and luggage storage areas following successive interior refurbishments.
- –Accessibility: Features universal-access toilets and wheelchair spaces to comply with modern rail accessibility regulations.
Routes and Passenger Services
The Class 168 fleet operates primarily on Chiltern Railways services connecting London Marylebone with High Wycombe, Bicester, Banbury, Leamington Spa, Warwick, Stratford-upon-Avon, and Birmingham Moor Street. According to operational updates from National Rail, these units also occasionally operate services on the Oxford to London Marylebone route following infrastructure upgrades completed under the Chiltern Railways Evergreen project.
Because of their rapid acceleration, 100 mph capability, and reliable diesel performance, the Class 168 trains remain vital for maintaining tight timetable schedules on mixed-traffic tracks shared with freight and intercity services.
Fleet Upgrades and Refurbishment
To maintain service reliability and passenger comfort, Chiltern Railways and rolling stock owners have undertaken several interior and mechanical upgrade programs for the Class 168 fleet. According to corporate announcements from Arriva UK Trains, these overhauls have included seat reupholstering, the installation of modern passenger information systems, and engine overhauls to reduce emissions and improve fuel efficiency across the fleet.
As the UK rail network progresses toward long-term decarbonization goals, the Class 168 remains a cornerstone of non-electrified regional transport in the Chilterns, bridging the gap between legacy diesel fleets and future zero-emission rail technologies.