Transport for Wales has completed the full electrification of the Core Valley lines, at the heart of the South Wales Metro.
The final 800 metre section between Cardiff Queen Street and Cardiff Bay was officially energised on Sunday 22 March, bringing the entire 170km network to 100% electrification and completing a six-year transformation programme that began in 2020. There will, however, be temporary service revisions to integrate the new programme.
Dubbed the ‘Welsh Tube’, the £1bn project brought electric tri-mode trains to the South Wales Valleys for the very first time in 2024. This spring, TfW will introduce the first of its 36 fully electric Class 398 tram-trains. The new fleet will initially operate between Pontypridd and Cardiff Bay, providing greener, more frequent services as part of the South Wales Metro.
Passengers are benefitting from these improvements with the Core Valley lines being one of the most punctual and reliable networks in Great Britain over the past 6 months.
Since work began in 2020, TfW and its partners have delivered an intensive programme of specialist engineering which includes:
- 5 miles of overhead wires installed
- Over 3,100 steel posts and 8,200 small steel parts installed to hold the wires in place.
- 14 railway track lowers completed to install wires under bridges.
- Five substations installed.
- Extensive vegetation clearance and fencing renewals to keep the network safe from trespass.
Working closely with partners Amey Infrastructure Wales, TfW introduced a world-leading Smart Electrification System that combines wired and wire-free sections made possible by innovative tri and bi-mode trains, capable of switching seamlessly between overhead electric power and battery.
The approach has delivered carbon and cost reductions compared with traditional fully wired systems, while avoiding the need for lengthy and disruptive bridge closures.
Timeline:
- 2020: Work begins to install Overhead Line Equipment (OLE) across the Core Valley Lines.
- 2023: First lines electrified through Aberdare, Merthyr, and Pontypridd to Cardiff
- Early 2024: Treherbert line electrified following nine months of extensive engineering works.
- 2025: Coryton and Rhymney lines electrified, marking 99% of the CVL network electrified.
- 22 March 2026: Cardiff Bay section officially energised, marking 100% electrification of the CVL network.
- The Core Valley Lines include the Treherbert, Aberdare, Merthyr, Coryton, City, Rhymney and Cardiff Bay lines.
- The electrification supports the introduction of new Class 398 tram trains on the Treherbert, Aberdare, Merthyr and Cardiff Bay lines, alongside the introduction of Class 756 tri mode trains on the Rhymney, Coryton, Penarth, Barry Island and Vale of Glamorgan lines.
- Through its No Second Chances safety campaign, TfW has already delivered rail safety sessions to more than 42,000 young people across the Valleys.
- Once the rollout of new rolling stock is complete and final signal upgrades are complete, this will enable faster journeys and more frequent services across the Core Valleys Lines.
Cabinet Secretary for Transport and North Wales, Ken Skates said, “This is a landmark day for rail in South Wales. We are finally seeing our ambition become a reality thanks to our unprecedented investment of more than £1bn to transform the CVL, with £800 million on new trains, and years of hard work and commitment from TfW.
“New, faster, modern trains, offering increased capacity and more frequent services helping to transform passenger experiences.
“This is another significant milestone on our mission to transform our railways.”
Dan Tipper, Chief Infrastructure Officer at Transport for Wales, added, “Completing the electrification of the Core Valley Lines is a landmark achievement for our infrastructure teams and construction partners. This has been one of the most complex engineering programmes undertaken in Wales in recent decades and delivering it safely and efficiently is a testament to the skill and dedication of everyone involved.
“I’m immensely proud of the work delivered and the benefits it will unlock for passengers across the Valleys, with greener and faster services connecting communities.
“We’re hugely grateful to our communities who have at times been heavily impacted by the work. They will now be able to reap the benefits of the improvements through faster, greener, more frequent and reliable services.”
Temporary changes to Cardiff Bay services
- TfW will be making temporary changes to services from 22 March until Friday 22 May to support the introduction of the first tram-trains which will initially run from Pontypridd to Cardiff Bay.
- During this period, the half-hourly Pontypridd to Cardiff Bay service will not run. However, the Cardiff Queen Street to Cardiff Bay shuttle service will continue to operate, with its frequency increased to four services per hour to maintain connections to Cardiff Bay.
- Passengers travelling from the Valleys to Cardiff Bay will need to change at Cardiff Queen Street, where Cardiff Bay services will depart from Platform 1. TfW are advising all passengers travelling to and from Cardiff Bay to check before they travel whilst these temporary changes are taking place.
