Rail services are experiencing “major disruption” with journeys cancelled or suspended due to “urgent repairs” needed on a bridge on Sunday and into Monday.
The work near Cardiff Central station has affected a number of routes run by Great Western Railway, Transport for Wales and CrossCountry, according to National Rail.
Rail replacement transport is being organised between Newport and Cardiff Central, and Cardiff Central and Caerphilly.
“Major disruption is expected until the end of the day on Monday 21 April,” said National Rail.