In March 2007 the latest in a series of infrastructure improvements on the Valley Lines was announced, which included lengthening of platforms between Rhymney and Penarth to allow Class 150 units to operate in multiples of 3 (6 cars).

However, this is postponed indefinitely due to the sub-lease by the Department for Transport, to Great Western Railway, of the units that would have allowed this extra capacity.

The line currently has a 15-minute daytime headway between Bargoed and Cardiff, with most journeys terminating at Barry Island or Bridgend.

North of Bargoed, two trains per hour runs over the single track, including the passing loop at Tir-Phil, to Rhymney.

The Sunday service operates over the entire length of the line every 1 hour since 2019, though this now runs all the day since Dec 2005.

[6][7] Preliminary re-signalling work on the route, which saw the remaining manual signal boxes at Heath, Ystrad Mynach and Bargoed abolished in favour of remote control from the new Cardiff Rail Operating Centre, was completed in early September 2013.

[9] However, as part of Welsh Government's South Wales Metro this line has been taken over,[10] and will soon be electrified[11] in preparation for new Class 756 rolling stock.