First Great Western is encouraging customers travelling over the Bank Holiday weekend to check journey times and routes.
Network Rail is completing £45 million works to redouble the railway line between Swindon and Kemble, as well as carrying out additional improvement works.
As part of this, the line between Bristol Parkway and Swindon will be closed on Saturday and Sunday.
This means the line will also be closed:
• Between Swindon and Didcot Parkway;
• Between Swindon and Gloucester;
• The Transwilts route - Swindon to Chippenham and Chippenham to Westbury via Melksham - will be closed;
• And the line between Hereford and Worcester Shrub Hill will be closed for rail improvement work.
Rob Mullen, FGW general manager, Central, said: “These are vital infrastructure works to help pave the way for increased capacity and reduced journey times, and better performance and punctuality that electrification and new electric trains will bring for future services.
“We have worked closely with our colleagues at Network Rail to keep disruption to a minimum.”