Train travel into and out of south Wales will be disrupted this weekend as work continues to electrify the main line.
There will be no trains to Cardiff and Newport, so buses will replace trains.
Part of the A465 Heads of the Valleys road is also closed this weekend.
As part of the £800m upgrade, the road between Abergavenny and Brynmawr is shut until 6am on Monday as work continues.
Trains from England to south Wales will start and terminate at Bristol Parkway, Cwmbran and Chepstow - and passengers will have to use buses to complete their journey.
Buses will also replace trains on the route between Ebbw Vale and Cardiff over the weekend.
The closures are due to Network Rail engineers installing overhead lines in the Newport, Cardiff and Bristol areas in order to prepare the route for electrification.
Passengers are advised to check before travelling this weekend.