This new viaduct and redoubling of the railway through Gowerton will remove the current bottleneck created by the stretch of single line and provide capacity to run more trains in the future.
This project joins a number of other rail improvement projects in South and West Wales that will help deliver better journeys and boost economic growth in the area.
As well as making it easier to travel to and from West Wales, they will help to boost local employment opportunities.
More top news
Britain's oldest supermarket worker Reg Buttress has passed away at the age of 95 - a few months after he retired.
Matthew Scully-Hicks passed the rigorous adoption process with "flying colours" and seemed "eminently suitable", according to judge.
Dyfed-Powys Police say it investigated reports of historical child sexual abuse by a monk at Caldey Island near Tenby.