Network Rail has thanked residents for their patience following the completion of upgrade work between Swansea and Port Talbot.
The work will make the railway more reliable for passengers.
Over the weekend, engineers worked throughout the day and night to remove old signal structures on the railway between Swansea and Port Talbot and to bring into use the new signalling system.
The £60m investment is the latest phase of the South Wales re-signalling programme and has seen the installation of 160 miles of new cable, 55 new LED digital signals, 160 metres of new track and new buffers at Swansea station.
There will be changes to some weekend services between Cardiff and Carmarthen on Saturday 9, Sunday 10, Saturday 23, Sunday 24, Sunday 31 March and Sunday 7 April, as Network Rail engineers undertake follow up works.
What did the officials say?
Mark Neate, project manager for Network Rail Wales and Borders, said:
“We would like to thank the local community and rail passengers for bearing with us whilst we delivered this work.
“The new signalling system between Swansea and Port Talbot will make the railway more reliable and resilient for passengers as it will allow railway traffic to be operated in either direction on the line. Although I understand disruption is never ideal, the work we have delivered will benefit rail users for many decades to come.”