Friday 8 May 2026
Innovative Severn Tunnel upgrade to transform key rail link between South Wales and England
Region & Route: Wales & Western: Wales & Borders
Working inside Severn Tunnel
Passengers are advised to plan ahead as Network Rail carry out major upgrade in the Severn Tunnel and Bristol area, with replacement buses and diversionary routes in place to keep people moving from late May to early June.
This vital project will see Network Rail, and contractors ARQ, complete the transformation of the Severn Tunnel’s overhead power system, designed specifically to withstand the tunnel’s harsh, corrosive environment - making it more resilient, reducing the frequency of maintenance, and helping to minimise disruption for passengers.
The work will take place around the clock from
Saturday 23 May until the early hours of Tuesday 9 June, with
the railway closed between Newport and Bristol Parkway during this time.
The new system
Running beneath the Severn Estuary, the 4.35-mile Severn Tunnel is one of the toughest environments on the UK rail network, where moisture and saltwater accelerate wear on equipment.
Since electrification, the overhead power system has been prone to corrosion and electrical wear, leading to more frequent maintenance.
To address this, Network Rail’s Wales and Borders team has developed and successfully trialled an innovative new system.
It uses a single 7km copper contact wire supported at regular intervals by modified bridge arms, to eliminate previous corrosion issues and improve performance.
Engineers will now install this system along the full length of the tunnel - using a world-first approach on this scale - to create a more resilient railway and reduce the need for frequent maintenance.