The railway line through Welshpool and Newtown could be closed for two weeks in May to allow a major overhaul ready for the introduction of new trains later this year.
Network Rail said that it will carrying out “essential infrastructure improvements” including a complete track renewal near Montgomery.
Rail passengers travelling between Montgomeryshire and the Borders are encouraged to plan ahead, as essential engineering works will affect services between Aberystwyth and Shrewsbury.
The Cambrian line work is expected to take place from Friday, May 8 until Friday, May 22.
The work will prepare the line for the introduction of Class 197 trains later this year, and will help to maintain a safe and reliable railway for both passenger and freight services in the future.
Network Rail said that the programme of work has been carefully planned to minimise disruption, with the line set to fully reopen in time for the May half term.
The work will include:
Gwyn Rees, Programme Director at Network Rail Wales and Borders, said: “These essential upgrades will help us maintain a safe and reliable railway for passengers and freight services across mid Wales and the Borders. We’ve carefully planned this work to minimise disruption, wherever possible, with the line due to fully reopen in time for the May half term
“We’d like to thank passengers for their patience while we carry out these important improvements.”
During this period TfW has organised rail replacement buses to ensure customers can continue to travel, including dedicated services to support local schools and colleges along the affected routes.
Colin Lea, Planning and Performance Director at Transport for Wales, said: “We know this will be a disruptive period for customers travelling across mid-Wales and the borders, and we’d like to thank everyone for their patience while these essential improvements are carried out.
“With different sections of the railway closed on different days between May 8-22, it’s really important that customers travelling between Aberystwyth, Pwllheli, Shrewsbury, Hereford and Llandrindod plan ahead and check their journey before travelling, using our website or app.
“These upgrades are a vital step towards introducing our brand-new Class 197 trains on the Cambrian line later this year, which will bring improved comfort and capacity for customers.”