page_title: British Rail Class 171
section_title: Design
hierarchical_section_title: British Rail Class 171 / Design
caption_attribution_description: The difference between Class 170 and 171 - Class 170 on the left has a BSI Compact coupler whereas the Class 171 on the right has a Dellner coupler for emergency compatibility with the Southern EMU fleet.
context_page_description: The British Rail Class 171 Turbostar is a type of diesel multiple-unit train built by Bombardier Transportation at its Derby Litchurch Lane Works in England, which is identical to the Class 170, except for the replacement of the BSI coupler with a Dellner coupling. This provision was made to allow emergency joining with Class 377 DC third-rail electric units, which Southern runs extensively on most lines. The vehicles work on the southern regions of the British railway system, operating services from London Bridge to Uckfield and from Eastbourne to Ashford International, these routes being unelectrified between Hurst Green Junction and Uckfield and between Ore and Ashford International, respectively.
  The fleet is operated by Govia Thameslink Railway for Southern services.
context_section_description: The Southern fleet is fitted with coupling devices (Dellner) different from other Turbostars, and is classified as Class 171 for this reason. The four-car units were built with the new couplers, but Class 170 two-car units were fitted at a later date, and reclassified as Class 171/7 after the modification. Three more two-car units were later acquired, but these were built from new with the new couplers.
  Southern gained the 170 392 unit from South West Trains. The coupler on this unit has also been changed to the Dellner type. The unit has been reclassified and renumbered from 170 392 to 171 730. This unit was first delivered carrying Southern livery and the number 170 727 (because SWT needed another 170 and it was cheaper to place another unit on the Southern order than place a new order). It never operated in this form and was transferred to South West Trains where it became 170 392.
  These trains have electronic onboard displays and automated next station announcements.
caption: Class 170 on the left has a BSI 'Compact' coupler whereas Class 171 on the right has a Dellner coupler.
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