Transport for Wales (TfW) has unveiled plans to add space for an additional 6,500 passengers each week from December.
It also announced plans to introduce more trains across the Wales and Borders rail network.
As per the plan, the Valley Lines will receive additional four-carriage trains during peak hours, which will help it transport additional 6,500 passengers per week.
Modern Class 170 trains will be introduced on the line between Cheltenham and Maesteg, as well as between Cardiff and Ebbw Vale.
In addition to more space, these trains will feature on-board passenger information systems, air conditioning, accessible toilet, Wi-Fi and power sockets.
Some services between North Wales and Manchester will use ‘Mark 4 intercity’ carriages. Additionally, a loco-hauled service will be provided on the Holyhead-Cardiff route, which links North and South Wales.
To make up for the delayed Class 769s, Porterbrook will supply additional Class 153 trains till the Class 769s are available.
Porterbrook CEO Mary Grant said: “Some of TfW’s plans depend on our innovative Class 769 trains, whose introduction into service has been subject to delays for which we apologise.
“In the meantime, we have accelerated delivery of our Class 170 units and are also supplying additional trains to cover for the Class 769s and provide support to TfW and their passengers.”
TfW has planned to keep the Pacer trains in service for a short period next year.
Once the Class 769s are available for service, TfW will gradually remove the Pacers and Class 37 loco-hauled trains from service.
TfW CEO James Price said: “We have always focused on delivering what our customers want, and we will do all we can to provide further capacity, which is their key priority. We must remain responsive to the needs of all of our customers, even if this means changing our plans.”