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The electrification of the Rhymney line is due to be completed in the coming days, Transport for Wales (TfW) has said.

According to the Welsh Government-owned company, the overhead wires are due to go live soon – although planned engineering works on Saturday December 6 and Sunday December 7 will mean rail replacement buses between Cardiff and Rhymney (full details below).

This final piece of work will see the 25km stretch of rail between Rhymney and Caerphilly electrified. 

The Cardiff Bay line is due to go live in early 2026, completing electrification of the South Wales Metro network.

Electrifying the upper Rhymney line enables TfW to introduce tri-mode trains (capable of running on electric, diesel, and battery power) replacing the last of the legacy diesel rolling stock currently operating on the line.

The electrical cabling is not continuous along the line however, with some sections of track unable to have it – such as Llanbradach station’s listed footbridge. This is where the newer trains will switch to battery power.

According to the website Rail Engineer, services will be able to run from Rhymney through Cardiff and onwards to Barry Island and Bridgend. As the track south of Cardiff Central is under the ownership of Network Rail – and not TfW – the new trains will run on diesel on the non-electrified track.

Dan Tipper, Chief Infrastructure Officer at Transport for Wales, said: “The electrification of the upper Rhymney line has been made possible by eight months of intensive work by our infrastructure teams, including installing 903 steel structures supporting over 33km of overhead wires and laying 30km of high-voltage cable. I’d like to thank our teams for working around the clock to achieve this major project milestone.

“We would also like to thank our local communities for their patience as this transformation work was carried out through the day and night, as well as during disruptive railway closures over the Easter and summer holidays.” 

TfW has recently launched a safety campaign reminding people that trespass on a railway line is illegal – and potentially lethal with electrified overhead lines carrying 25,000 volts.

According to the firm, there has also been a recent rise in cable theft along the Rhymney line and security has been boosted. It is also urging the public to remain vigilant and to contact British Transport Police if they spot any suspicious behaviour.

Engineering works on Saturday December 6 and Sunday December 7

The Rhymney line will be closed between Rhymney and Cardiff Queen Street on Saturday December 6 and Sunday December 7. During the closure, all railway stations, station footbridges, and level crossings from Rhymney to Caerphilly will be closed.

Rail replacement services will be in operation during the closure.

To avoid the Christmas shopping traffic in the city centre, on Saturday December 6, TfW will run buses from Cardiff Central to Bargoed (not stopping at Cardiff Queen Street) and from Cardiff Queen Street to Rhymney.  

On Sunday December 7, rail replacement services will depart from Cardiff Central as normal, stopping at Cardiff Queen Street.