Network Rail is carrying out a major upgrade, which will undoubtedly cause headaches for passengers who live between two key UK citiesRachel Vickers-Price UK and World News Reporter and Jon King07:40, 27 May 2026Significant works on a four-mile tunnel will temporarily shut down a stretch of railway line between two cities. Rail passengers are being advised to plan their journeys in advance as Network Rail undertakes a major upgrade at the Severn Tunnel from 23 May until 9 June.‌The rail network operator confirmed that its work alongside contractor ARQ would overhaul the tunnel's overhead power system to better withstand the tunnel's "harsh, corrosive" environment. Nia Watkins, Regional Asset Manager at Network Rail Wales and Borders route, said: "Running beneath the Severn Estuary, the 4.35-mile Severn Tunnel is one of the most challenging environments on the UK rail network."‌She stressed that carrying out the works was vital to sustaining safe, dependable services and securing the tunnel's long-term future.‌Ms Watkins added: "This complex and highly coordinated upgrade is being delivered at a world-first scale across the tunnel's full length - making the railway more resilient and reducing the risk of future disruption for passengers and freight."Network Rail describes the tunnel as one of the most demanding environments on Britain's railways, with moisture and saltwater accelerating the deterioration of equipment, reports the Express.‌Network Rail noted that since electrification, the overhead power system has been susceptible to electrical wear and corrosion.Its Wales and Borders team is deploying a single 7km copper contact wire supported by modified bridge arms to "eliminate" corrosion. According to Network Rail, the new system will run the entire length of the tunnel in a "world-first" at this scale.This encompasses 838 bridge arms to support the electrical cables, a total of 9,000 metres of replaced wiring and additional infrastructure improvements.‌Alongside the tunnel works, Network Rail confirmed it is also replacing track serving the new Bristol Brabazon station.Network Rail stated the station will mark the return of passenger services on the Henbury and Portishead lines for the first time since 1964.The works mean the railway between Newport and Bristol Parkway will temporarily close.‌Services will not operate between Newport and Bristol Parkway from Saturday, May 23 until the end of Monday, June 8. The line is expected to reopen on the morning of Tuesday, June 9.Replacement bus services will run between Newport and Bristol Parkway while some trains will travel between London and South Wales via Gloucester, except on Sunday, May 24. There will be a reduced service between London Paddington and Bristol Parkway.‌Trains will not be diverted via Gloucester on May 24, with services running solely between Paddington and Bristol Parkway as well as Newport and Swansea.Marcus Deegan, GWR's Station Manager at Bristol Parkway, said: "We know bus replacement services are a significant ask of passengers and we're genuinely grateful for their patience while this vital work is completed."This investment to improve and maintain the Severn Tunnel will make a real difference to the reliability and resilience of the route for many years ahead.Article continues below"The wider work taking place will also allow us to introduce train services to Bristol Brabazon later this year, and in time to Portishead and Pill - reconnecting people to rail and providing a vital economic catalyst across the area."