Network Rail’s upgrades will take place from Monday 6 July until Sunday 2 August, with further work scheduled over Saturday 8 August and Sunday 9 August. The work will affect services between Swindon and Bristol Parkway.
Trains will continue to run throughout the engineering programme, but journeys between London Paddington and South Wales are expected to take around 25 minutes longer.
Services between Swindon and Bristol Parkway will also be reduced to one train per hour while the work is carried out. There will be no rail replacement buses during the disruption.
Great Western Railway (GWR) said it will operate additional services between London Paddington and Swindon to provide more travel options for passengers travelling on that section of the route.
Some trains will also have revised stopping patterns to help maintain a reliable service during the engineering work.
The project includes track renewals west of Swindon and major structural improvements inside Chipping Sodbury Tunnel. Network Rail said the investment will improve reliability and help protect the railway from the effects of extreme weather.

Marcus Deegan, GWR’s Station Manager for Swindon and Bristol Parkway, said:
“This is an important investment in the future of the route, and we want customers to feel the benefit of it for years to come.
“We know longer, less frequent journeys are an inconvenience in the short term, so we’re doing everything we can to help, including extra services to and from Swindon and we’d encourage everyone travelling this summer to plan ahead and check before they go.
“Trains will continue to run throughout the work, and our teams will be on hand to help customers complete their journeys.”
Michael Pinkerton, Network Rail portfolio manager, said: “This work will make the railway more resilient and reliable for passengers long into the future.
“Our teams will be working day and night throughout the summer to deliver these upgrades as efficiently as possible, minimising disruption while we strengthen the route against extreme weather.”
Passengers are being advised to check their journeys before travelling and reserve seats where possible.
The work forms part of a wider programme to improve the resilience and reliability of the Great Western main line, with the aim of reducing delays and delivering a more dependable service in the future.

















