Transport for Wales to Convert Class 231 Fleet into Hybrid Trains

Transport for Wales (TfW) has confirmed plans to upgrade its Class 231 fleet, with the diesel-electric trains set to be converted into hybrid units as part of the organisation's long-term decarbonisation strategy.

The move follows an agreement between TfW, the Welsh Government and manufacturer Stadler to activate a Hybrid Variation Agreement, paving the way for the installation of pantographs and the introduction of electric operating capability across the fleet.

The Class 231 fleet, comprising 11 trains built by Stadler, currently operates on a range of services across South Wales alongside TfW's Class 756 units and Class 150 trains. Once converted, the trains will be capable of drawing power from overhead electrification where available while retaining the flexibility to operate beyond electrified sections of the network.

The upgrade is expected to play a key role in supporting the next phase of the South Wales Metro programme, which will see Class 398 tram-trains introduced on core valley routes over the coming years.

As newer vehicles enter service, the Class 231 fleet is expected to be redeployed onto longer-distance routes, including services on the Vale of Glamorgan Line and other main line corridors across the Welsh rail network.

TfW says the conversion programme will deliver both operational and environmental benefits. By making greater use of electric traction, the trains will reduce diesel consumption, lower carbon emissions and decrease noise levels, particularly in urban areas and around stations.

Alexia Course, Chief Commercial Officer at Transport for Wales, said work is now being prepared following funding approval from the Welsh Government and agreement with delivery partners.

She said the project would help reduce reliance on diesel-powered operations while providing greater flexibility in how the fleet is deployed across the network.

The programme will be delivered in stages over several years, allowing trains to remain in service while modifications are carried out.

The decision reflects a wider trend across the UK rail industry, where operators are increasingly looking to retrofit existing rolling stock rather than replace entire fleets. Hybrid technology is seen as a cost-effective way of accelerating decarbonisation while making use of existing infrastructure investments.

For Transport for Wales, the conversion of the Class 231 fleet represents another step towards its ambition of creating a cleaner, more sustainable railway while improving operational efficiency and supporting the wider transformation of rail services across Wales.