Class 170

Class 170
Name	Class 170
Service	1998–present
Manufacturer	Bombardier Transportation (Derby Litchurch Lane Works)
Family	Turbostar
Yearconstruction	1998–2005
Numberbuilt	139 sets
Formation	2/3 cars per set
Operator	Transport for Wales, ScotRail, CrossCountry, London North Eastern Railway, West Midlands Trains, Northern Trains
Lines	West Coast Main Line, East Coast Main Line, Cross Country Route, West Midlands rail network, Welsh Marches line
Carbody	Aluminium
Doors	Double-leaf sliding plug
Traction	Diesel-hydraulic
Maxspeed	100 mph (160 km/h)

Class 170 is a family of diesel multiple unit passenger trains built by Bombardier Transportation at Derby Litchurch Lane Works as part of the Turbostar family. Introduced in the late 1990s, they have been used by multiple UK operators on regional and intercity services across routes including the West Coast Main Line and the Cross Country Route. The units replaced older diesel fleets such as the British Rail Class 156 and British Rail Class 158, and have seen refurbishments, reconfigurations, and transfers between operators over decades.

Design and construction

The design evolved from the Turbostar concept developed by ADtranz and Bombardier Transportation at Derby Litchurch Lane Works, incorporating aluminium car bodies, double-leaf sliding plug doors, and modular interiors similar to Class 168 and Class 159 derivatives. Construction used assembly techniques refined from work on Class 170's forbidden name-related families, with bogies derived from Bombardier B5000 designs and diesel powerpacks influenced by MTU Friedrichshafen installations used in continental multiple units. Prototype testing occurred on the Network Rail test circuits and the Old Dalby Test Track, overseen by regulators including the Office of Rail Regulation.

Technical specifications

Typical sets are formed as two-car or three-car formations with aluminium off-centre cab longitudinal designs, seating layouts fitted for regional services, and HVAC systems meeting Rail Safety and Standards Board guidelines. Each car is equipped with a MTU diesel engine rated to deliver acceleration and a maximum speed of 100 mph, braking systems based on Knorr-Bremse air equipment, and safety systems compatible with Train Protection & Warning System and route signalling on the West Coast Main Line and East Coast Main Line. On-board features include passenger information systems interoperable with standards used by Transport for Wales and ScotRail, accessibility provisions complying with the Rail Vehicle Accessibility Regulations 2010, and multiple-unit coupling compatible with other Turbostar family members.

Variants and subclasses

Operators acquired different batches with interior and mechanical variations, leading to subclasses distinguished by formation, interior fit-out, and minor technical differences similar to subclass differentiation seen between British Rail Class 158 and British Rail Class 159. Some batches were built with higher torque engines for steep-gradient routes on networks such as the West Highland Line, while others had first-class sections and catering provisions intended for longer-distance services like those on the Cross Country Route. Depot allocations and fleet numbers followed practices established at depots such as Tyseley TMD, Cardiff Canton Depot, and ScotsGarner Depot.

Operations and deployment

Units have operated with a range of operators including Transport for Wales, ScotRail, CrossCountry, London North Eastern Railway, West Midlands Trains, and Northern Trains, serving routes such as the Welsh Marches line, Cumbrian Coast Line, and inter-regional links connecting Birmingham New Street, Cardiff Central, Manchester Piccadilly, and Newcastle. They frequently replaced older British Rail DMUs and were cascaded as electrification projects like Great Western Main Line electrification and regional timetable changes altered rolling stock allocations. Maintenance cycles are conducted at regional depots including Swansea and Saltley Depot, coordinated with Network Rail timetabling and Office of Rail and Road oversight.

Refurbishment and modifications

Several operators have carried out interior refurbishments, new seating, accessible toilets, and installation of modern passenger information systems, following examples of mid-life updates seen on fleets like Class 158 refurbishment programmes. Modifications have included retrofitting of full-width gangways for unit coupling compatibility inspired by practices on Turbostar family members, fitting of ex-service sets with controlled emission toilets to meet environmental standards promoted by the Environment Agency, and repainting liveries to reflect franchising changes involving Arriva and FirstGroup branding.

Incidents and safety

Throughout service, some units have been involved in operational incidents, collisions, and derailments investigated by the Rail Accident Investigation Branch and sometimes prompting recommendations to the Office of Rail and Road. Investigations have cited factors including signalling failures on routes like the West Coast Main Line and infrastructure defects under Network Rail management, leading to safety advisories and fleet modifications such as enhanced cab protection and revised maintenance regimes at depots like Tyseley TMD.

Preservation and heritage units

A small number of vehicles and components have been preserved by heritage groups and museums including institutions similar to the National Railway Museum and volunteer societies that preserve diesel multiple unit heritage. Preserved examples are occasionally used in heritage events and galas on preserved lines associated with organizations like the Heritage Railway Association and regional trusts connected to North Yorkshire Moors Railway and other heritage railways.

Category:British diesel multiple units