Balfour Beatty has completed the work to electrify the 77km Bristol-Cardiff rail line on the Great Western Railway (GWR) line.
It carried out the work on behalf of Network Rail as part of the Greater West Electrification Programme. The programme aims to electrify 275km of the rail line between Cardiff and London.
Around 750 Balfour Beatty operatives were a part of the final works. They installed the overhead cables at Cardiff Central Station.
Balfour Beatty erected more than 4,200 masts and booms, which support 643km of electric cabling along the 77km route.
The first electrified train operated on 6 January from Cardiff Central Station.
Balfour Beatty Rail business MD Mick Rayner said: “We are proud to have successfully delivered part of the largest modernisation project on the Great Western Railway, which we have been working on for the past three years.
“Delivering this important upgrade to the Welsh rail network will provide a more sustainable way of travelling for tens of thousands of commuters.”
Network Rail route managing director Mark Langman said: “I am delighted that services can now run on electricity between Bristol and Cardiff, linking the two capital cities for the very first time via an electric railway.
“This is the culmination of the largest modernisation project on the Great Western railway since it was built in Victorian times, which we have been working on over the last 10 years.”
Last year, a joint venture (JV) comprising of Balfour Beatty, Vinci and Systra won a contract from High Speed 2 to manage the construction of Old Oak Common station.
The JV is responsible for the design, construction and commissioning of the station located in north-west London.
Balfour Beatty also secured a contract worth around £220m from Transport for London (TfL) to deliver London Underground track renewal works.