This line linked up with the TVR line from Cardiff to Pontypridd and the Llantrisant (Pontyclun) on the GWR.
More details on the dates of construction and abandonment can be found here (RAILSCOT website). The main purpose of this page is to show what is left of this route. The table on the right details the current state of the line. There is a photogallery at the bottom of the page.

The map exerpt below shows railways in the Llantrisant area from a 1982 1:200,000 O.S. road atlas (Crown Copyright) and the original Llantrisant & Taff Vale Junction Railway insignia, prior to merger with the TVR

	The section between the TVR main line and Tonteg was abandoned in the 1930s due to its high gradient. A loop was built to connect with the Barry railway at Tonteg, with a new halt being built. The joint railway joined the main line at Treforest, on the Llantwit Road Station site (opposite the university).
	On the original route, abandoned in 1938, little remains between the Tonteg bridge and Llantrisant Junction. The Tonteg Road Bridge was removed in the 1990's for road widening / straightening works. Maes Mawr Road Bridge (by the site of the original Tonteg Halt), formerly an iron girder bridge has been partially removed. only the stone abutments remaining. Nothing of the halt remains and the trackbed is muddy and overgrown towards the Barry Railway Bridge.
	The loop between the Barry Railway Bridge and Tonteg Junction is also somewhat overgrown. The section just south of the Maes Mawr road bridge is relatively clear. The track is at a higher level than the Barry Railway track.The new Tonteg halt platform is still extant, but heavily oergrown. Access is via the fromer station acces path. North of Maes Mawr road, the Barry/ TVR loop trackbed is private property, used for keeping horses.
	From Tonteg Bridge to Crown Hill Road bridge, including the stations at Church Village and Llantwit, the trackbed has been substantially overbuilt with new development. The bridges have been removed and thr stations demolished.
	To the west of Llantwit, the cutting is still accessible but overgrown to the footpath bridge. This bridge appears to have been re-topped post war with concrete parapets. The line is accessible for a short distance, including the site of the old Cwm Colliery junction. A section of about 1/4 mile from here to the new Cwm Colliery junction is private, overgrown and has been built on. From Cwm new junction to Beddau halt, the trackbed is walkable, with concrete sleepers in places.
	The track is accessable at Heol Dowlais Br but is overgrown and muddy. This is also the site of Beddau Halt. Apart from a gap between the bridge abutment and the trees where the stairway was, there is no sign of the halt now. Continuing to the west, the site of Beddau halt is not obvious, but some sleepers and the occasional rail remain. The trackbed continues, overgrown to A473 Llantrisant Rd bridge, walkable with difficulty to Common Branch Junction.
	The triangle fromed by Common Branch Junction is heavily overgrown on the western limbs, however the Llantrisant Branch itself is relatively clear. Sleepers and some track remains, including an old style footpath level crossing.
	Between Common Branch Junction and Maesraul Junction, including Cross Inn station the track is variably overgrown by brambles and young trees, especially near Maesraul Junction. Sleepers are in place for the whole section, which is complete with rails south of Cross Inn Station. The platform is still there, and the old station house now serves as a motor service establishment. The entire section from Beddau Bridge to Cardiff Rd Bridge is walkable, probably easier in the spring before the brambles grow - good blackberry picking though...
	Maesraul Junction has track for the TVR branch, but treack for the GWR quarry spur has been lifted. The trackbed of the GWR is being built upon. The section between Cardiff Rd Bridge and A4119 Llantrisant road is heavily overgrown. Mwyndy Junction....?
	Section between Mwyndy Junction and Llantrisant/Pontyclun station is abandoned but tracks are still in place, including level crossing gates on A473 Llantrisant bypass.