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
The Taff Vale Railway had a branch line to Llancaiach, where there were productive collieries. This spate of railway building in South Wales, mirroring that in England, encouraged thoughts of a railway serving the Rhymney ironworks. An agreement was reached with the Taff Vale Railway that it would convey the Rhymney traffic over its line from Llancaiach. Separate dock facilities at Cardiff would be provided, at what became Bute East Dock.