02 Dec 2025

Transport for Wales has taken another major step towards completing the electrification of the South Wales Valley lines, as the overhead wires across the Rhymney railway line are switched on.

This major step in the electrification of the South Wales Metro network follows the completion of engineering work on the 25km stretch between Caerphilly and Rhymney. The final section along the Cardiff Bay line is due to be electrified in early 2026.  

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 across the line.  

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.” 

As the electrification of the Rhymney line marks another milestone for the South Wales Metro project, TfW reminds the public that trespassing on the railway line is illegal and poses serious risks, especially on electrified lines, as they carry 25,000 volts. Due to the increased dangers of electrocution, no one should attempt to trespass onto the railway.  

Through its No Second Chances safety campaign, TfW is continuing to highlight the risks of trespass with young people across the Valleys. With the help of its education provider Bollo, over 42,000 students would have received a session on railway safety by the end of 2025.   

TfW is also encouraging the public to remain vigilant due to a recent rise in cable theft attempts along the Rhymney line. Whilst enhanced security patrols are now in place, any suspicious activity, including anyone attempting to access the railway, should be reported to the British Transport Police on 0800 40 50 40 or text 61016. For emergencies, call 999.