Britain's railways and signals operator, Network Rail, has asked the government for an extra £7 billion in funding to invest in the future.
The firm, which also runs 17 of the country's major stations, believes that substantial changes are needed in order to meet the challenge of an increase in passenger numbers.
And it has asked the government to help fund these changes, with much of the money being earmarked for use in and around London.
"About £3 billion of [the money] will go towards the Thameslink programme, which has been in gestation now for many years and is absolutely essential to meet increasing demand in London," Network Rail chief executive John Armitt told the Today programme.
"London Waterloo Station needs to be redeveloped. Birmingham New Street Station needs to be redeveloped. We need to improve the freight lines between Southampton and the north of the country.
"In Scotland there are major projects at both airports that are required. Those are just some of the larger schemes. There are a whole series of smaller ones."
He added: "They carry an absolutely critical element of the travelling public, which is the commuters which go every day in and out of London, Manchester and Birmingham. Main cities in the north and in Scotland also carry a very large proportion of the inter-city transport in this country."
Mr Armitt added that today's request represented the start of a two-year discussion between the firm, the government and the Office of Rail Regulation and that Network Rail was aiming to reduce the running costs of the railway system by about £1 billion a year.
Network Rail recently revealed pre-tax losses of £232 million in 2005-06, an increase of £185 million from 12 months earlier.