MAJOR work is due to start on the rail line between Swansea and Llanelli on March 24.
Arriva Trains Wales is advising passengers there will be changes to services until April 8.
The train operator said some trains will be diverted and will not call at Swansea.
There will be a limited train service between Cardiff and Swansea.
Replacement bus services will be in operation between Swansea, Gowerton and Llanelli.
Buses will connect to train services to and from Cardiff and West Wales and the Heart of Wales line.
Network Rail is carrying out the two weeks of work.
Posters about the service changes have been put up at train stations.