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Class 231 FLIRT
Stadler's four-car diesel FLIRT, with its engines in a short power pack car in the middle of the train, away from the passengers. Transport for Wales's 11 work from Rhymney to Cardiff and Barry Island, Maesteg to Ebbw Vale, and Cardiff to Cheltenham; they are to be fitted with pantographs and become bi-modes.
Scale
265 ft (80.7 m) over couplers
Class 231 FLIRT · schematic drawing GB Trains · gbtrains.uk/stock/231/ · CC BY 4.0
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- Type
- Diesel-electric multiple unit
- Builder
- Stadler, Bussnang (Switzerland)
- Family
- FLIRT, with Class 745 FLIRT, Class 755 FLIRT, Class 756 FLIRT
- Built
- 2021–2022
- In service
- since 2023
- Operators
- Transport for Wales
- Formation
- 4 passenger cars and a short power pack car: 265 ft (80.7 m) over couplings
- Trains in fleet
- 11
- Fleets
- Transport for Wales: 11
- Top speed
- 90 mph (145 km/h)
- Power
- Diesel-electric: four Stage V diesel generator sets in the power pack car, 1,920 kW (1,500 kW at the wheel) · how it works
- Bogies
- Stadler FLIRT bogies, with Jacobs bogies between cars · drawn with the same bogie component as Class 745 FLIRT, Class 755 FLIRT, Class 756 FLIRT
- Train length
- 265 ft (80.70 m)
- Car height
- 12 ft 10 in (3.915 m)
- Car width
- 8 ft 11 in (2.72 m)
- Profile
- main-line
- Air-conditioned
- Yes
- Seats per train
- 170
- Total capacity
- 170 seats, 34 tip-up and 188 standing (Stadler); 204 seats including tip-ups (TfW)
- Status
- In service: 11 units, maintained at Canton, Cardiff. In June 2026 TfW confirmed that pantographs will be fitted over the coming years. Owned by SMBC Leasing and Equitix.
Car types
| Code | Car | Length | Doors per side |
|---|---|---|---|
| DMSO | Driving motor standard open (DMSO) | 69 ft 1 in21.05 m | 2 double |
| TSO | Trailer standard open (TSO) | 51 ft 6 in15.70 m | 1 double |
| PP | Power pack car (PP) | 23 ft 7 in7.20 m | |
| TSOW | Trailer standard open with wheelchair spaces and toilet (TSOW) | 51 ft 6 in15.70 m | 1 double |
Sources
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Show the 23 sources from Wikimedia Commons, Stadler, Transport for Wales Rail Ltd and 6 more
- BR Class 745 Triebdrehgestell (photograph, CC0) Wikimedia Commons (Plutowiki), 15 October 2018, at the Velim test circuitthe FLIRT motor bogie's layout (photograph: layout only)
- BR Class 745 Laufdrehgestell (photograph, CC0) Wikimedia Commons (Plutowiki), 15 October 2018, at the Velim test circuitthe FLIRT trailer bogie's layout (photograph: layout only)
- TfW 231008 articulated bogie (photograph, CC BY-SA 4.0) Wikimedia Commons (Geof Sheppard), 20 February 2023, Cardiffthe FLIRT Jacobs bogie's layout (photograph: layout only)
- FLIRT diesel-electric multiple unit, Transport for Wales (data sheet FWBDMU0423e) Stadler, April 202311 units; 265 ft (80,700 mm); width 8 ft 11 in (2,720 mm); height 12 ft 10 in (3,915 mm); floor 3 ft 2 in (960 mm); 170 seats, 34 tip-up, 188 standing; 1,920 kW diesel, 1,500 kW at wheel; 90 mph (145 km/h); Bo'2'2'2'2'Bo'
- CVL Vehicle Change notice: Class 231, Core Valley Lines (except Cardiff Bay), entry into service Amey Infrastructure Wales for Transport for Wales Rail Ltd, 8 September 2022formation DMSO1-TSO-PP-TSOW-DMSO2; doors; 154.3 t; 90 mph (145 km/h); maintained at Canton; first unit delivered November 2021
- Transport for Wales launches Class 231 Flirt DMUs Railway Gazette International (Rail Business UK), 29 March 2023launch at Caerphilly, 29 March 2023; first on the Rhymney line, replacing Class 769s
- A guide to our fleet of trains: fleet accessibility specifications (V3, updated June 2026) Transport for Wales, June 202611 units; 170 seats and 34 tip-up; routes (June 2026)
- Transport for Wales confirms '231' fleet will become bi-modes RAIL, 3 June 2026pantographs to be fitted to all 11, confirmed June 2026
- Case study: Wales & Borders, commercial and contract management Apex Rail, accessed 7 October 2026owned by SMBC Leasing and Equitix
- British Rail Class 231 Wikipedia, accessed 7 October 2026first passengers 18 January 2023; bodyshells from Szolnok (last resort)
- FLIRT diesel-electric multiple unit, Transport for Wales (data sheet FWBDMU0423e) Stadler, April 2023, p. 2side elevation (measured): doors, windows, car lengths, bogies
- Class 231 FLIRT unit at Ninian Park, Cardiff, 11 April 2022 (photograph, CC BY 2.0) Wikimedia Commons (Jeremy Segrott, from Flickr), 2022door layout and livery (layout and colour only)
- 756 001 at the depot in Barry, 28 April 2023 (photograph, CC BY-SA 4.0) Wikimedia Commons (Geof Sheppard), 2023livery placing and colours, the same as the 756s' (layout and colour only)
- Transport for Wales Class 756 FLIRT TMU (photograph, 27 May 2025, CC BY-SA 4.0) Wikimedia Commons (Samson Ng, D201@EAL), 2025the power pack car's livery (layout and colour only)
- 756 117 at Aberdare, 19 November 2024 (photograph, CC BY 4.0) Wikimedia Commons (Anamyd), 2024livery colours (colour only)
- Class 175 Livery Design [Driving Vehicles] and [Centre Vehicles] Transport for Wales Rail Ltd (released under FOI: 'Livery designs for current rolling stock'), released 9 September 2021TfW's livery colours (the drawing's fills, as on the Class 175)
- Class 769 Transport for Wales Livery Concept, Option 6, DG8-SK-92454 Issue C Transport for Wales Rail Ltd (released under FOI: 'Livery designs for current rolling stock'), 8 February 2019 (released 11 August 2021), p. 1paint references for TfW's red and grey scheme
- Class 150 Transport for Wales Livery Concept C, Option 1, DG8-SK-92444 Issue B Transport for Wales Rail Ltd (released under FOI: 'Livery designs for current rolling stock'), 21 November 2018 (released 11 August 2021), p. 1paint references for TfW's red and grey scheme
- FLIRT tri-mode multiple unit, Transport for Wales (data sheet FWBTRI0922e) Stadler, September 2022, p. 2the cab front as one smooth curve fitted to the body shell, the lamp hood, wiper and fittings masked (set CA, ca-flirt; measured)
- FLIRT tri-mode multiple unit, Transport for Wales (data sheet FWBTRI0922e) Stadler, September 2022, p. 2the cab's joints and the lamp lens, side on (set FL5)
- Class 745 Cerhenice.jpg (photograph of 745001 on test, Plutowiki, CC0) Wikimedia Commons, 26 April 2019the cab side window's dark rubber frame, about 30 mm (set FL5)
- Caerdydd Canolog - Northern 150269 a TfW 231005.JPG (photograph, CC BY-SA 4.0) Wikimedia Commons (Geof Sheppard), 28 April 2023the cab coupler: its kind, place and heights (set BC6, 20 October 2026; layout only for photographs)
- Caerdydd Canolog - TfW 756106 llaes 231006.JPG (photograph, CC BY-SA 4.0) Wikimedia Commons (Geof Sheppard), 25 June 2025, p. photographthe window band's top beside the door, about 9 ft 3 in (2,825 mm; set T11)
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- Car lengths: measured off Stadler's side view, not printed (Stadler gives only the 265 ft (80.7 m) unit): 69 ft 1 in (21.05 m) driving cars, 51 ft 6 in (15.70 m) trailers and a 23 ft 7 in (7.20 m) power pack car between bogie centres, the same as the Class 755's within 5 mm
- Build years: TfW received the first unit in November 2021 and expected the eleventh in September 2022 (2022 notice); Wikipedia says the bodyshells were made at Szolnok, Hungary
- First passengers: Wikipedia, citing The Railway Magazine, gives 18 January 2023; the formal launch was on 29 March 2023 (Railway Gazette)
- Owners: SMBC Leasing and Equitix, from a consultant's case study (Apex Rail)
- Height: Stadler prints 12 ft 10 in (3,915 mm); the drawing's roof is 11 ft 11 in (3,643 mm), its fairings 3,770, the cab top 3,837 and the power pack car's roof 3,850, so 3,915 is presumably over roof equipment
- Drawing: which trailer has the toilet isn't visible from outside (Stadler draws a wheelchair sign on both); the cars are named in the order of TfW's 2022 notice, DMSO1-TSO-PP-TSOW-DMSO2
- Livery: the colours are the fills of TfW's Class 175 livery drawings (FOI), as on the site's 175; no drawing or paint reference for the FLIRTs was found; the placing of the black window panels, red roof, orange line and red front is from photographs (mostly of 756s, in the same livery)
- The power pack car's livery is from photographs of a 756's; the 231's looks the same in Stadler's and Commons photographs
- The grey boxes under the driving cars' low floor are drawn as on the Class 755 (from a photograph of 755 334): indicative
- The cab front: one smooth curve fitted to the body shell on Stadler's Class 756 sheet (FWBTRI0922e, p. 2), the lamp hood, wiper and fittings masked and a 27-33 mm dip above the lamp bridged; the dome's top comes out at 12 ft 8 in (3,850 mm; 3,837 before); compared with photographs of 756001 (nearly side-on) and 745001 for its shape only
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