New tri-mode trains are set to be introduced on the Vale of Glamorgan Line next year.
The Class 756 trains, which can run on electric, diesel or battery, were rolled out on the Penarth line in the summer as part of the South Wales Metro.
TfW says it has seen improvements on the line since the new trains were introduced with more reliability and fewer cancellations, having previously admitted services to and from Penarth were not good enough.
Kelsey Barcinella, a stakeholder manager at TFW told Bro Radio's 'The Vale This Week': "Next year, we'll be rolling out some of our new trains on the Merthyr, Aberdare and Treherbert lines, which then frees up the 756 trains onto other parts of the network such as the Rhymney line and the Vale of Glamorgan."
"You'll start to see more services using our newer trains, and then, from our next timetable changes through next year, we'll start to see the uplift in frequencies and realiability across the network."
Other timetable changes, taking effect on Sunday, include a new early morning service from Bridgend to Cardiff - calling at all stations - and post-midnight trains running to Cardiff to Treherbert, Aberdare and Merthyr aimed at boosting the nighttime economy.
Transport Secretary Ken Skates said: "Rail connectivity is absolutely vital in driving prosperity."
"These changes will make a real difference to customers, who will benefit from more services and greater connectivity. This has been made possible by our £800m investment in brand-new trains for the Wales and Borders network."
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