Work on the South Wales Metro project will continue this Autumn, but Transport for Wales is urging passengers to check before travelling due to route closures.
Brand new electric trains are set to operate on the Merthyr, Aberdare and Treherbert lines from the Autumn.
Following the June change, more trains are already running between Pontypridd, Caerphilly, Rhymney and Cardiff.
Significant work is now needed this Autumn, which will mean rail replacement buses operating on some Valley lines.
The route from Merthyr Tydfil, Aberdare, Treherbert to Radyr will close and no trains will be running between 28th September to Sunday 6th October.
Instead, rail replacement buses will operate. Trains that do run will start and terminate at Radyr.
On the 6th of October, an extra bus service will run for the Cardiff Half Marathon, as well as an additional morning rail service from Radyr to Cardiff.
This closure is a mere 9 days rather than the 23 days previously communicated with passengers.
During the closure, engineers are set to carry out work that is essential to allow Transport for Wales to increase train frequency to four per hour from the head of each valley.
Planned work will include track and signalling upgrades to Pontypridd station, the removal of the Treforest footbridge for donation to a heritage railway and trackside cleaning throughout the network.
Later on in October, engineering work will take place at Cardiff Queen Street in preparation for more trains to run through the station.
The work is set to take place between Sunday 27th October and Sunday 3rd November and as the station is a major junction for the Valley, City and Cardiff Bay lines, a number of services will be affected.
No trains will run on the Coryton, Rhymney and Penarth lines.
Please check with Transport for Wales for the latest travel information.
