Wales' busiest railway station will be "significantly" upgraded and a new station will link the west to the south, it has been announced.
UK Transport Secretary Chris Grayling said £58m would be spent on revamping Cardiff Central and West Wales Parkway would be built in Felindre, Swansea.
The move will also see journey times between Wales' two biggest cities cut by up to 14 minutes.
Mr Grayling said people in Cardiff "deserve a modern, accessible station".
The Department for Transport said the upgrades would ease crowding and congestion during peak periods.
Mr Grayling said: "This funding has the potential to deliver just that, ensuring more reliable, comfortable and faster journeys into and out of the capital."
Annual passenger numbers are predicted to rise from 12.7 million in 2016 to 32 million by 2043.
Transport expert Prof Stuart Cole said Cardiff Central had become a victim of the city's success as an "events holder".
"It's a 1930s station which was never built for the task it now does with commuters, but also sports events and concerts," he added.
"The Wales-England rugby match this year saw 37,000 people moved by train very successfully, but very slowly, over four hours."
As well as £40m from Cardiff's city deal, the project was dependent on funding from UK and Welsh governments.
Welsh Secretary Alun Cairns added: "The way in which the station operates is not fit for purpose in terms of a modern day capital city.
"We are also committing to progressing plans for a West Wales Parkway station, which will deliver time savings of up to a quarter of an hour from Pembrokeshire to Cardiff and increase local connectivity around Swansea to provide greater opportunities for the whole of the Swansea Bay City region."
Prof Mark Barry, who drew up the first proposals for the south Wales Metro project, said: "In general, any further investment or money for Welsh railways is to be welcomed."
But he added: "If you want faster journeys to west Wales you can run a fast train, as has been discussed on the Swansea District Line, and run it non-stop.
"To stop the train in Swansea slows down journeys to west Wales.
"So I support the parkway concept, but it has to be developed in respect of a broader proposal for the whole of the Swansea bay."
The West Wales Parkway scheme - estimated to cost about £20m - would be built on a line mainly used for freight and it is hoped it will cut the number of cars on the M4.
Mr Cairns said he was "really excited" about the project, adding it would connect communities that previously had limited access to rail links with Swansea, south Wales and Cardiff.
The Welsh Government said: "Being six times busier than any other railway station in Wales, Cardiff Central is in desperate need of investment to improve the experience for its users, to enhance its capacity and to future-proof it."