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.
Hengoed Viaduct
The line opened as a double track as agreed in 1858. Integrated as part of the Great Western Railway during the railway grouping in 1921, in 1928 the entire length of the Taff Vale Extension was downscaled to a single track.