Overview
The British Rail Class 171 is a member of the Turbostar family of diesel multiple units (DMUs) introduced for regional and suburban services in the United Kingdom. Operated primarily by Southern, these units serve routes that include non-electrified sections and complement the operator’s electric fleet. The Class 171 combines the basic Turbostar design with specific changes to suit Southern’s operational needs.
Design and characteristics
Mechanically and internally the Class 171 shares much with other Turbostar types. It features a modern welded aluminium or steel body, flexible multiple-unit controls, and passenger amenities appropriate for short- to medium-distance routes. Typical features include seating for commuters, vestibules for standing passengers, and provisions for accessibility. Performance is comparable to sibling types, with cruising and top speeds suitable for mixed urban and regional timetables.
Key differences and compatibility
The most notable distinction between the Class 171 and its close relative the Class 170 is the coupling equipment. While many Turbostar units use the BSI coupling, the Class 171 was fitted with a Dellner coupler. This deliberate change allows mechanical, pneumatic and electrical connections to be made with Southern’s third-rail electric units when required. In practice this enables emergency rescue or towing and limited operational coupling with specific electric trains such as the Class 377.
Characteristics at a glance
- Family: Turbostar series
- Type: Diesel multiple unit (DMU)
- Coupling: Dellner, enabling compatibility with Southern EMUs
- Typical use: commuter and regional passenger services on partially non-electrified routes
History and operational role
The Turbostar family was introduced to replace older diesel units and to provide a standardized, modular design that operators could adapt. The Class 171 reflects this approach: rather than a separate design, it is a tailored variant produced to meet the interface and rescue needs of one operator. Southern has used these units to ensure continuity of service on routes that connect to electrified lines, benefitting from the ability to couple to electric units in exceptional circumstances.
Importance and notable facts
The Class 171 demonstrates how a common train family can be modified to meet network-specific requirements. Its Dellner couplers improve operational resilience by allowing emergency joining with compatible electric multiple units, which is particularly useful on a network that mixes third-rail electrification with diesel-operated branches. For more information on the Turbostar family and related types, see resources about the Turbostar, diesel multiple units in general via DMU references, the closely related Class 170, and the electric Class 377 used by the same operator.