The new Transport Secretary has backed the high-speed HS2 rail project.
Chris Grayling vowed not to scrap HS2, easing fears of those concerned it may have been scrapped by new Prime Minister Theresa May's Government.
Mr Grayling emphasised that the line is as much about capacity as it is about speed and said it would help ease congestion on overcrowded trains.
"I have no plans to back away from the HS2 project," he told BBC Radio 4's The World This Weekend.
"And 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.
"The West Coast mainline for example is becoming really congested, it's limiting the capacity of services to places like Northampton and Milton Keynes.
"HS2 has always been a capacity project as much as a speed project.
"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."
Meanwhile, Mr Grayling said he wants to make a rapid decision on airport capacity.
His predecessor Patrick McLoughlin warned that the timetable for a new runway set out by the Airports Commission might only be met if a decision on whether to back projects at Heathrow or Gatwick is taken by October.
In 2009 it was reported that Mr Grayling, who is MP for Epsom and Ewell, Surrey, privately voiced concerns over the Conservative Party's then-opposition to Heathrow expansion.
Mrs May's constituency, Maidenhead, is near the Heathrow flight path and she has previously raised the issue of noise and the environmental impact of a third runway at the airport.
The Airports Commission published its final report in July last year stating that a new runway was needed by 2030 and recommending that Heathrow's plan should go ahead.
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."
He added: "What I'll be saying to the business community today is I think we need to take a rapid decision to provide certainty on what's going to happen and that will be my objective."
A spokesman for Heathrow said: "We welcome the Transport Secretary's comments promising a rapid decision on airport expansion today.
"Heathrow expansion has significant business and political support across the country and is the best way to keep the UK a great trading nation post Brexit."