The new transport secretary, Chris Grayling, says he does not intend to scrap the high-speed HS2 rail project.
The initial plan is for a new line from London to Birmingham, with later extensions to Manchester and Leeds.
Mr Grayling told BBC Radio 4's The World This Weekend: "I have no plans to back away from the HS2 project."
The new transport secretary also said he wanted to reach a quick decision on where a new runway should be built to meet growing demand for air travel to and from London.
On rail, Mr Grayling told the BBC: "The thing that's important for people to understand is that HS2 is not simply a speed project, it's a capacity project.
"We have lines at the moment which have seen huge increases in the number of passengers, the amount of freight in recent years."
He said the West Coast main line was becoming "really congested" and was limiting the capacity of services to places such as Northampton and Milton Keynes.
Mr Grayling added: "Of course it makes sense if we're going to build a new railway line for it to be a fast railway line, to increase travel times or reduce travel times from north to south - that's logical.
"But actually we need a better transport system for the 21st century and HS2 is part of increasing the capacity of our transport system."
On flight capacity for the South East, the Airports Commission published a report last year that said a new runway was needed by 2030, and recommending that Heathrow's plan for a third runway should go ahead.
An alternative option would be to build a second runway at Gatwick - an idea supported by London's mayor, Sadiq Khan. Another suggestion has been doubling an existing runway at Heathrow.
Mr Grayling said: "I am very clear that I want to move rapidly with a decision on what happens on airport capacity. It is a decision that will be taken collectively by the government.
"We have a quasi-judicial role so I'm not going to say today whether I prefer Gatwick or Heathrow, there's two options at Heathrow. I'm going to look at this very carefully in the coming weeks."
MPs are due to vote on the first phase of the HS2 project later this year. Their approval of the bill should allow construction to start on the London to Birmingham section.
The company building the line, HS2 Ltd, is also set to hand out £11bn worth of contracts in the coming months.