Network Rail have announced planned engineering work between Gloucester and Chepstow from Monday May 12 until Friday May 16.
This work will see all lines closed between Lydney and Gloucester during the duration of the works.
They are closing the lines due to major track improvements but will be providing late-night rail replacement bus services travelling in both directions.
The closure will ensure that the new 700 yards of track near Lydney can be laid out and work can be completed safely and efficiently.
The buses will run from Severn Tunnel junction and Gloucester/ Cheltenham Spa.
You can find out more information about the rail replacement buses and how this will affect your journey on the Network Rail website.