More than 4,000 extra daily peak rail seats into London will be available from 2018 after First Group extended its deal to run services on the Great Western network until 2019.
First Great Western will pay the government around £68m to run the franchise - which operates services between London, the Cotswolds, South Wales and the South West - from September 2015 until April 2019.
As well as increased seat availability on morning peak times there will be 3 million additional seats a year by 2018 across the First franchise, faster journeys between Penzance and Paddington and London to south Wales, Oxford and Bristol.
There will be a £30 million investment to improve stations and car parks, including 2,000 more car park spaces and the introduction of electric train services for the first time on the network, starting with services in the Thames Valley.
Transport Secretary Patrick McLoughlin said: “I am determined that passengers in the west, Thames Valley and South Wales get a railway that is fit for the 21st century. This is a fantastic deal which will give them more seats, more services and brand new fleets of modern trains.
“This government knows the importance of our railways. That is why they are a vital part of our long term economic plan, with over £38 billion being spent on the network between 2014 and 2019.”
First Group has operated the Great Western network on its own since 1998 when it took 100% ownership of the franchise.