First Capital Connect route to get 41 extra carriages.
More than £27 million funding will see more frequent and longer trains and extra seats for commuters on the First Capital Connect 'Great Northern' route into London.
The Great Northern route connects Moorgate and Kings Cross stations in London with stations to the north of the capital such as Welwyn Garden City and Hertford North.
41 extra carriages will see an extra 3,800 seats connecting Moorgate and an extra 2,750 connecting King's Cross.
The key improvements include four extra morning services into London Moorgate from either Gordon Hill or Welwyn Garden City, three additional evening services to either Gordon Hill or Hertford North from London Moorgate and the lengthening of a number of existing services serving London Kings Cross or London Moorgate.
In the longer term the Government and train operator also plan to increase the number of 12-car services on the line following the completion of supporting infrastructure works including power supply upgrades and the lengthening of platforms at six stations including Royston, Letchworth, Arlesey, Biggleswade, Sandy and Finsbury Park.
The Government have also pledged to introduce an extra 1,300 rail carriages onto the rail network.
Neal Lawson, Managing Director at First Capital Connect, said: "The extra trains will see significant increases in capacity for our customers, especially at the busiest times of day."
"We will be adding additional services and strengthening existing services to six, eight and twelve carriages long - bringing thousands of extra seats from this December onwards."
First Capital Connect