New electric 'tri-mode' trains are being rolled out for the first time onto the South Wales Metro network.
Transport for Wales says the Class 756 trains - which can also use diesel or battery power on non-electrified routes - are being introduced on the Merthyr and Aberdare lines first, followed by the Treherbert line.
But passengers in the eastern Vale of Glamorgan will have to wait until late next year before the new fleet is brought into service locally.
TfW says the phased introduction will see fourteen 'tri-mode' trains introduced by next Spring on the electrified Valley lines - the first service of its kind in the UK.
James Price, TFW's chief executive, said: "Our teams and delivery partners have been working on transforming our rail infrastructure in South Wales for the last three years and this signifies the next phase of the South Wales Metro."
"We’ve been modernising and electrifying the railway line and we are now extremely proud to be able to introduce the first of our brand-new trains that will be powered by electricity."
"We’ve already introduced sixty-five brand-new trains to the whole of our network and we’re excited to now add our Class 756 electric trains that will offer customers more capacity, improved seating, modern air conditioning, power sockets, WiFi and passenger information screens with up-to-the-minute travel information. They’ll also feature automatic level boarding and space for up to six bikes."

From late 2025, the Class 756 trains will start moving over to the Rhymney and Vale of Glamorgan lines, when the new tram-trains enter passenger service on the Valley lines.
From then on, the 756s will run from Rhymney to Barry Island and Bridgend and from Coryton and Caerphilly to Penarth.
In June, major timetable changes saw new Class 231 trains removed from the Penarth line just over a year after they were introduced and moved to services covering Barry and Barry Island.
More recently, services to and from Penarth have also been affected by engineering works as part of the Metro project.
But TFW says the transformation of the Core Valley Lines will enable faster and more frequent services between Cardiff and the heads of the valleys.
Emil Hansen, commercial project manager for Stadler - which built the new trains - added: "We are thrilled to see the UK’s first FLIRT tri-mode enter passenger service in Wales."
"Using battery technology, these transformative rail vehicles represent a significant leap forward in Transport for Wales’ efforts to drive decarbonisation and underscore Stadler’s trail-blazing technology and commitment to clean energy."

Vueling withdraws winter flights to Aicante this winter
Playground in Barry forced to close after fire damages equipment
Campaigners Take Fight for Fairer Pathways in Welsh Women’s Football to Parliament
Vale Councillor Gwyn John Launches His First Novel at Llantwit Major Book Signing
Pink poppy display commences with celebration of life
Former Barry office block converted into new homes for people at risk of homelessness
Welsh Government publishes independent report on Level 4 intervention at Cardiff and Vale UHB
Three CoastSnap stations set to be installed along the Glamorgan Heritage Coast
Daffodil Runner statue installed at Marie Curie Hospice in Penarth
Woman Dies After Incident in Leckwith as Police Investigation Continues
Vale entrepreneur wins national Innovate UK award for sustainable construction technology
Cardiff Airport retains top accessibility rating as regulator reports record demand for assistance
Open Doors event to showcase hidden world of Glamorgan Archives
New details have emerged of a new tree-lined public square that will replace a traffic dominated junction
Dyffryn Gardens’ Edwardian rose garden blooms again after decade-long restoration
Barry’s Own Daniel White to Walk 190 Miles Back to Where His Round Table Story Began
1,300 people attend Flying Start Family Fun Day
Dispersal order put in place to tackle anti-social behaviour
Interim Chief Executive Appointed at Cardiff and Vale University Health Board
Cardiff Theatre Marks 50 Years of Service for Long‑Standing Staff Member