The Severn Tunnel has reopened to passengers following a six-week closure to prepare it for the electrification of the line in 2019.
Closed since September 12, Network Rail has been installing a conductor rail system throughout the 130-year-old tunnel.
The project is central to the electrification of the Great Western Main Line between London Paddington and Cardiff.
In all, 14 kilometres of conductor rail have been installed during the closure. Other preparatory works, including removing more than 40 tonnes of soot within the tunnel, were also carried out.
Mark Langman, Network Rail’s Western route managing director, said: “We are delighted to have delivered this vital milestone in the project to electrify the Great Western Main Line as part of our Railway Upgrade Plan to give passengers a bigger and better railway.
“We would like to thank passengers for their patience over the last six weeks as we completed this essential upgrade.”
Dan Tipper, project director at Network Rail, added: “It has been a phenomenal team effort, involving over 250 engineers and close working with our principal contractors ABC Electrification and Babcock as well as numerous suppliers, designers and sub-contractors including Amco, Keltbray and Arup, to deliver this essential stage of the electrification project.
“I would like to thank every single member of the team that has worked on this iconic project for their hard work and dedication to deliver this upgrade successfully and on time.”