Llantrisant and Taff Vale Junction Railway
In time the Canal became overwhelmed by the volume of traffic, and encouraged by the successful opening of railways with more advanced technology than the horse tramways of previous years, the Taff Vale Railway was promoted. It was authorised by Parliament in 1836 and it opened between Merthyr and Cardiff docks in 1841. The line passed close to the Maesmawr workings but did not make a connection.
Rhymney Railway
In 1871 another, short branch was opened: it was from Ystrad Mynach on the RR main line to Penalltau Junction on the Taff Vale Extension line. By this time the Great Western Railway had taken over the Newport, Abergavenny and Hereford Railway (through its successor, the West Midland Railway) so the Taff Vale Extension was GWR territory. The line had been extended to Middle Duffryn in the Aberdare Valley, and connected there with the Vale of Neath Railway, also now controlled by the GWR. As part of the deal when the Taff Bargoed line was agreed with the GWR, the Rhymney Railway had secured running powers through Aberdare to Hirwain.