Class 155

Class 155 is a designation used for a family of diesel multiple units associated with regional United Kingdom services and has also appeared in other national railway contexts. The designation links to rolling stock developments tied to manufacturers, operators, and regional authorities such as British Rail, Network SouthEast, ScotRail, Northern Trains, and private groups like Arriva and Stagecoach Group. The type is notable in connection with design programs undertaken by firms including British Rail Engineering Limited, Metro-Cammell, Bombardier Transportation, and preservation efforts by organizations like the National Railway Museum, Heritage Railway Association, and independent preservation societies.

Design and development

The design and development phase involved collaborations among industrial stakeholders such as British Rail Engineering Limited, Metro-Cammell, and design consultancies linked to projects like the InterCity 125 and Sprinter family programs. Engineering teams engaged with regulatory bodies including the Rail Safety and Standards Board and infrastructure authorities such as Network Rail and regional transport executives like Transport for London and Transport for Greater Manchester. Prototype activities referenced earlier initiatives such as the Mark 2 coach upgrades, the TOPS classification system, and lessons from fleets like the Class 150 and Class 156. Project milestones intersected with procurement frameworks used by Ministry of Transport and later by devolved administrations including Scottish Executive and Welsh Government. Industrial design drew influence from collaborations between Rolls-Royce plc powerplant divisions and suppliers like Voith and Cummins for transmissions and engine management.

Technical specifications

Technical specifications aligned with standards promulgated by British Standards Institution and rolling-stock compatibility considerations from Network Rail route gauging and signalling standards like TPWS and AWS. The units typically featured drivetrain components from firms such as Cummins and MTU Friedrichshafen GmbH and hydraulic transmissions by Voith. Bogie designs referenced developments used on the Mark 3 coach and the suspension technologies trialed on prototypes from British Rail Research Division. Onboard electrical systems were influenced by suppliers such as Siemens and Alstom, while braking systems were comparable to those fitted on Class 158 and Class 159 units. Passenger accommodation standards referenced the Rail Vehicle Accessibility Regulations and interior suppliers including Fife Fabrications and Balfour Beatty contracts for depot support. Weight, speed, and seating capacity conformed to performance envelopes similar to the Sprinter family DMUs and compatibility with regional depots like Heaton TMD and Tyseley TMD.

Operational history

Operational history includes deployment across routes administered by franchises such as Regional Railways, Arriva Trains Northern, FirstGroup, and legacy operations under British Rail. The units served lines connecting cities like Manchester, Leeds, Glasgow, Edinburgh, Birmingham, and commuter corridors into London Liverpool Street and Bristol Temple Meads. Service patterns intersected with timetable changes overseen by the Office of Rail and Road and franchise agreements awarded to companies including Northern Trains, ScotRail, and East Midlands Railway. Operational experience drew lessons from contemporaries such as Class 150, Class 156, and Class 170, and maintenance regimes were influenced by depot practices at locations like Leeds Neville Hill depot and Haymarket depot. Incidents in service prompted reviews by investigators from Rail Accident Investigation Branch and policy responses discussed in parliamentary committees including the Transport Select Committee.

Refurbishment and upgrades

Refurbishment and upgrades were implemented under contracts with engineering firms like Bombardier Transportation, Alstom, and independent contractors such as Knorr-Bremse and Wabtec Corporation. Upgrades addressed accessibility in line with Rail Vehicle Accessibility Regulations, introduced passenger information systems from suppliers like Thales Group and Siemens, and involved seating, HVAC, and lighting improvements referencing best practice from refurbishments of Class 150 and InterCity 125 fleets. Onboard safety systems were retrofitted to comply with TPWS, AWS, and later national standards; depot upgrades mirrored investments in facilities funded by programs connected to Department for Transport grants and regional transport bodies including Transport for Wales.

Accidents and incidents

Accidents and incidents involving units in this designation prompted investigations by bodies such as the Rail Accident Investigation Branch and responses from operators including Network Rail and franchise holders like Arriva and FirstGroup. High-profile events were debated in forums including the Transport Select Committee and influenced regulation by the Office of Rail and Road. Technical faults identified led to parts replacements sourced from manufacturers like Voith and Cummins and to operational changes documented in industry publications such as Railway Gazette International and Modern Railways.

Preservation and current status

Preservation and current status reflect transfers to heritage organisations including the National Railway Museum, regional societies such as the Keighley and Worth Valley Railway and North Yorkshire Moors Railway, and private preservation groups operating at locations like Severn Valley Railway and Mid Hants Railway. Remaining units saw varied fates: continued service with operators like Northern Trains and ScotRail, overhaul programs supported by engineering firms including Alstom and Bombardier, or static preservation at museums connected to institutions such as the Science Museum Group. Future prospects remain linked to fleet replacement strategies overseen by bodies including the Department for Transport and regional authorities such as Transport Scotland and Transport for Greater Manchester.