Transport for Wales (TfW) has marked a major milestone in the delivery of the South Wales Metro, partnering with Campaign for Better Transport to showcase the transformation of the Treherbert line—one of the UK’s most significant recent rail infrastructure upgrades.
Once characterised by legacy systems and ageing rolling stock, the Treherbert route has been comprehensively modernised, evolving into a fully electrified railway with cutting-edge signalling, new trains and upgraded passenger facilities.
Until early 2023, operations on the line relied on a Victorian-era ‘Token Exchange System’. Under this system, drivers were required to leave their cabs to collect a physical token before entering single-track sections and return it at the other end. While historically reliable, the method was increasingly incompatible with the demands of a modern, high-frequency railway.
As part of TfW’s wider investment programme across the Valleys network, the removal of this outdated system became a critical step. The line was closed for nine months to allow intensive engineering work, including the installation of a modern digital signalling system. This is now controlled remotely from TfW’s £100 million depot and control centre at Taff’s Well.
The transformation also reflects a shift towards smarter ticketing and passenger convenience. Contactless pay-as-you-go has rapidly gained traction, with over 4.5 million journeys recorded across the South East Wales Metro network as passengers adopt tap-in, tap-out travel for best-value fares.
A key component of the upgrade has been the electrification of the Core Valley Lines, delivering overhead line equipment to the Treherbert route for the first time in its history. This has enabled the deployment of brand-new Class 756 trains.
Built by Stadler and introduced to the line in February 2025, the Class 756 Fast Light Intercity and Regional Trains (FLIRTs) are powered by 25kV overhead electrification. Notably, these ‘tri-mode’ units are the first passenger trains in the UK capable of operating using diesel, battery or electric power, offering flexibility across mixed infrastructure.
Alongside electrification and new rolling stock, the upgrade programme has delivered:
- Revised track layouts and passing loops
- Renewed sections of rail infrastructure
- Extended platforms to accommodate longer trains
- New ‘Access for All’ footbridges
- Enhanced passenger information systems
TfW is now preparing for the introduction of fully electric tram-trains between Pontypridd and Cardiff Bay later this summer, marking a further step towards a turn-up-and-go Metro-style service for communities across South Wales.
Marie Daly, Chief Operating Officer at Transport for Wales said:
“The Treherbert line is one of our biggest transformations as part of the South Wales Metro and we’re pleased to welcome representatives from Campaign for Better Transport to Wales and offer them the opportunity to visit the line and experience the wider South Wales Metro.
“We’ve been on a journey of transformation with rail in Wales and have replaced some of the oldest railway infrastructure with some of the most modern in Europe. Through this investment, we’ve also been able to remove older trains from the network and introduce brand-new, modern fleets, alongside electrification and upgraded infrastructure.
“Just a few years ago, ‘pacer’ trains were running on these lines; today customers are benefiting from faster, more reliable and accessible services that are designed around their needs. This transformation is already making a real difference—improving journey times, increasing capacity, and providing a more comfortable and sustainable experience for the communities we serve.
“None of this would have been possible without the dedication, resilience and professionalism of our amazing teams and partners, who have worked tirelessly to deliver such a complex programme of change while keeping services running for our customers.
“Most importantly, these improvements are helping to connect people to education, jobs and each other, creating stronger, more inclusive communities across South Wales.”
The visit coincides with Better Transport Week (15–21 June), an annual initiative led by Campaign for Better Transport to highlight how accessible, affordable and sustainable transport networks can support communities and economic growth. The event brings together stakeholders from across government, industry, business and passenger groups.
Michael Solomon Williams, from Campaign for Better Transport, said:
“I’m delighted be here in South Wales to celebrate this amazing transformation. Good public transport networks help connect us to the people we love, the things we need and the places that matter, creating thriving places and stronger communities, and building a fairer future for everyone.”
Image credit: Transport for Wales
