British Rail Class 231
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| British Rail Class 231 FLIRT | |
|---|---|
 Class 231 unit at Lisvane and Thornhill in 2023 | |
 Interior | |
| In service | 18 January 2023 – present |
| Manufacturer | Stadler Rail |
| Assembly | Stadler Bussnang AG |
| Built at |
|
| Family name | FLIRT |
| Replaced | |
| Constructed | 2021–2022 |
| Number built | 11 |
| Number in service | 11 |
| Formation | 4 cars per unit: DMS-TS-PP-TSW-DMS |
| Fleet numbers | 231001–231011 |
| Capacity | 170 seats, plus 36 tip-up & 180 standees |
| Owners | SMBC Leasing |
| Operators | Transport for Wales Rail |
| Depots | Canton (Cardiff) |
| Specifications | |
| Car body construction | Aluminium |
| Train length | 80.7 m (264 ft 9 in) |
| Width |
|
| Height | 3.915 m (12 ft 10.1 in) |
| Floor height | 960 mm (3 ft 2 in) |
| Doors | Double-leaf sliding plug, each 1.300 m (4 ft 3.2 in) wide (total 6 per side) |
| Wheel diameter |
|
| Wheelbase | Bogies: 2.700 m (8 ft 10.3 in) |
| Maximum speed | 90 mph (145 km/h) |
| Weight | 154.3 tonnes (151.9 long tons; 170.1 short tons) (4-car set) |
| Traction system | IGBT |
| Prime mover(s) | 4 × Deutz 16-litre V8 turbo-diesel |
| Power output | 1,500 kW (2,000 hp) at wheel |
| Tractive effort | Starting: 160 kN (36,000 lbf) |
| Acceleration | 0.9 m/s (2.0 mph/s) |
| UIC classification | Bo′2′2′2′2′Bo′ |
| Safety system(s) | |
| Multiple working | Within class (max. 3 units) |
| Track gauge | 4 ft 8+1⁄2 in (1,435 mm) standard gauge |
The British Rail Class 231 is a class of eleven diesel-electric multiple units of the FLIRT family, which have been built for Transport for Wales by Swiss rolling stock manufacturer Stadler Rail. The first units entered service on 18 January 2023.
History
The previous Wales & Borders rail franchise operator, KeolisAmey Wales ordered the new trains. Although KeolisAmey was removed as the franchise operator and replaced by an operator of last resort Transport for Wales Rail, owned by the Welsh Government, the scheduled full fleet replacement continued.
The units began testing in Switzerland in July 2021 and in November 2021 the first two units were delivered to Cardiff Canton depot.
Operators
Transport for Wales
The Class 231 units are currently used for services on the Rhymney line and the Vale of Glamorgan Line. They mostly operate between Rhymney/Bargoed and Barry Island from Mondays to Saturdays, and between Rhymney/Caerphilly and Barry Island on Sundays.
Sometimes they operate on other valleys lines as well such as the Merthyr/Aberdare Lines, the City Line and the Treherbert Line.
It is expected that they will operate the following services from around late 2025 or early 2026:
- Maesteg to/from Ebbw Vale Town via Cardiff
- Newport to/from Ebbw Vale Town
- Cardiff Central to/from Cheltenham Spa.
The official revenue launch of the Class 231 took place on 29 March 2023 at Caerphilly.
Technical details
Class 231 units have four passenger vehicles, along with a separate "Power Pack" vehicle at the centre of the unit that contains four diesel generator sets. The diesel generators comply with EU Stage V emissions regulations. All vehicles are linked by unpowered Jacobs bogies, while the outermost bogie at each end of each unit carries the traction motors.
As of October 2024, TfW are planning to convert their Class 231 units to hybrid units with pantographs (meaning they would become bi-mode units more like Class 755s), and have mobilised a project team to support the implementation of the conversion with Stadler.
Fleet details
| Subclass | Operator | Qty. | Year built | Passenger cars | Unit nos. |
|---|---|---|---|---|---|
| 231/0 | Transport for Wales Rail | 11 | 2021–2022 | 4 | 231001–231011 |
Illustration
Named units
- Unit 231001 is named Sultan. It was suggested by a local school as part of a competition run by TfW, and is named after a statue at Ystrad Mynach of the pit ponies used in the local coal mines.
- Unit 231005 is named Gavin & Stacey. It was suggested by a local primary school that participated in the Christmas Event at Barry Island which is part of the final episode of Gavin and Stacey.
| British Rail Class 231 FLIRT | |
|---|---|
Class 231 unit at Lisvane and Thornhill in 2023 | |
Interior | |
| In service | 18 January 2023 – present |
| Manufacturer | Stadler Rail |
| Assembly | Stadler Bussnang AG |
| Built at |
|
| Family name | FLIRT |
| Replaced | |
| Constructed | 2021–2022 |
| Number built | 11 |
| Number in service | 11 |
| Formation | 4 cars per unit: DMS-TS-PP-TSW-DMS |
| Fleet numbers | 231001–231011 |
| Capacity | 170 seats, plus 36 tip-up & 180 standees |
| Owners | SMBC Leasing |
| Operators | Transport for Wales Rail |
| Depots | Canton (Cardiff) |
| Specifications | |
| Car body construction | Aluminium |
| Train length | 80.7 m (264 ft 9 in) |
| Width |
|
| Height | 3.915 m (12 ft 10.1 in) |
| Floor height | 960 mm (3 ft 2 in) |
| Doors | Double-leaf sliding plug, each 1.300 m (4 ft 3.2 in) wide (total 6 per side) |
| Wheel diameter |
|
| Wheelbase | Bogies: 2.700 m (8 ft 10.3 in) |
| Maximum speed | 90 mph (145 km/h) |
| Weight | 154.3 tonnes (151.9 long tons; 170.1 short tons) (4-car set) |
| Traction system | IGBT |
| Prime mover(s) | 4 × Deutz 16-litre V8 turbo-diesel |
| Power output | 1,500 kW (2,000 hp) at wheel |
| Tractive effort | Starting: 160 kN (36,000 lbf) |
| Acceleration | 0.9 m/s (2.0 mph/s) |
| UIC classification | Bo′2′2′2′2′Bo′ |
| Safety system(s) | |
| Multiple working | Within class (max. 3 units) |
| Track gauge | 4 ft 8+1⁄2 in (1,435 mm) standard gauge |
Last updated 24 June 2025. All information and images sourced from the relevant Wikipedia article(s) unless stated otherwise. If any information is incorrect, please let us know by emailing us: [email protected]. Text is available under the Creative Commons Attribution-ShareAlike License 4.0; additional terms apply.