Transport for Wales has switched the Treherbert line from Victorian-era token-exchange signalling to digital control from its new £100 million depot at Taff's Well, following a nine-month closure that delivered full electrification.

What did the upgrade change on the ground?

Until early 2023, drivers on the Treherbert line left their cabs to collect physical tokens before entering single-track sections and returned them at the other end. The procedure dated to the 19th century. TfW closed the line for nine months to install modern signalling, lengthen platforms, build Access for All footbridges and renew track layouts and passing loops.

The line now carries 25 kV overhead wires for the first time. The wires feed Stadler's Class 756 FLIRT trains, which entered passenger service on the route in February 2025. TfW describes the Class 756 as the first UK passenger trains able to draw power from overhead wires, onboard batteries, or a diesel engine on non-electrified sections. The tri-mode configuration is branded FLIRT, or Fast Light Intercity and Regional Train.

How are passengers using the new infrastructure?

Contactless pay-as-you-go ticketing has recorded more than 4.5 million tap-in journeys across the South East Wales metro since launch. TfW attributes the figure to passengers moving from legacy fares to best-value contactless products.

The wider South Wales Metro programme has removed the Class 150-era "pacer" units from the Core Valley Lines and replaced them with the Class 756 fleet operating under the new overhead electrification.

What comes next on the Metro?

TfW is preparing to introduce its first new tram-trains on Pontypridd to Cardiff Bay services this summer. The tram-trains will share Core Valley Lines infrastructure with the Class 756 fleet, supporting turn-up-and-go frequencies the operator says are designed around valley communities rather than commuter peaks.

The Taff's Well depot and Control Centre, completed as part of the South Wales Metro investment, now oversees signalling across the upgraded Core Valley Lines section, with TfW staff controlling train movements from a single facility.

What do the operators and campaigners say?

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."

She added: "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."

Daly also said: "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."

Michael Solomon Williams of 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."

When did the visit take place?

The visit occurred during Better Transport Week (15–21 June 2026), the Campaign for Better Transport's annual event. Last year's edition drew support from more than 100 organisations, including the Department for Transport, local authorities, transport operators, NGOs, businesses and passenger groups.

The campaign, registered charity 1101929, operates in England and Wales and advocates for sustainable transport that reduces inequality and supports a decarbonised economy.

The Pontypridd–Cardiff Bay tram-train launch this summer will test whether Core Valley Lines infrastructure, much of which only emerged from token signalling in 2023, can sustain Metro-style frequencies on a sustained basis.