The Barry Railway had been able to access the Rhymney Railway since 1891, using the running powers on the Taff Vale Railway from Cogan to Taffs Well. As volumes of traffic increased, crossing the busy Taff Vale main line at Walnut Tree Junction became increasingly difficult and subject to delays. If the Barry Railway could make a more direct connection, it could also connect with the Sirhowy Valley line of the London and North Western Railway, and a huge new route would be opened up, enabling a general merchandise traffic between Cardiff and the West Midlands and North West of England as well as bringing down the mineral resources of the upper valleys.