Arriva Trains Wales operates a train from Cardiff to Aberfan hourly. Tickets cost $9 - $14 and the journey takes 41 min. Alternatively, you can take a bus from Cardiff to Aberfan via Merthyr Tydfil, Bus Station (Merthyr Tydfil Bus Station) in around 1 h 18 min.
From Cardiff Queen Street train to Merthyr Vale. 41 min £7. From Cardiff, Castle Stop KA (Cardiff Castle) bus to Merthyr Tydfil, Bus Station (Merthyr Tydfil Bus Station) then bus to Merthyr Vale, Station Square (Merthyr Vale Railway Station). 1 h 18 min £9. From Cardiff taxi to Aberfan. 27 min £51. From Cardiff drive to Aberfan. 27 min £3. From Cardiff Uber to Aberfan. 27 min £43.