A new ticket barrier, booking office and customer information screens are among new developments at Cardiff Central Station designed to make travelling smoother for commuters.
The changes will help with crowd control during peak periods - for example handling visitors to the Rugby World Cup - but also during the day-to-day running of the station.
The new station entrance at the south side of the station - the busiest in Wales - has been designed give passengers more space.
Wales Office Minister Alun Cairns said:
With the Rugby World Cup here in Cardiff, it is crucial that our rail network can manage the pressure and move thousands of people around quickly and comfortably.
It is great to see how Network Rails improvements will keep Cardiff Central station functioning at maximum capacity and continue to keep up with our vibrant capital city.
Tom Bye, project manager for Network Rail Wales, said:
The railway in Wales is carrying almost 50 per cent more passengers than it was 10 years ago and that number is predicted to grow significantly in the years ahead.
As we see more business investment on the south side of Cardiff Central station, we are seeing an increase in the number of passengers using the entrance. The wider station entrance will give passengers more space, allowing even more people to use the busiest station in Wales.
Wed like to thank passengers for their patience while work was being carried out and were delighted the new entrance opened in time to welcome fans from all over the world to Cardiff for the Rugby World Cup.
The art-deco booking hall sign, which dates back to the early 20th century, has been restored with help from the Railway Heritage Trust, and now hangs in the new booking office.
The Penarth Road car park has also been reinstated to its original layout.The south-side of Cardiff Central has been viewed as the rear of the station in the past, but Network Rail has made improvements to the entrance to cater for the increasing numbers of passengers using the entrance.
There are more businesses at the south-side of the station and more people using this entrance now than ever before to get to work or to the new Cardiff and Vale College, just 200m from Cardiff Central station. With further business investment as part of the Enterprise Zone anticipated, this passenger demand is expected to increase further.
The new entrance at the south-side of the station was opened in time for the Rugby World Cup, which kicked off last week.
Network Rail is also installing new track, new signalling and a new platform at the station, whilst causing the minimum disruption possible to passengers, as part of the Cardiff Area Signalling Renewal (CASR) project.