The government has said it intends to spend billions of pounds improving railways across England and Wales. Here's what you need to know about the announcement.
David Cheskin, PA Wire
Precisely how much is being spent?
The investment, which began in 2005 under the previous Labour government, will be completed by 2019 and will cost in total £9.4bn.
Does that figure include existing spending?
Yes. Today's announcement confirmed £5.2bn worth of funding for ongoing projects, such as Crossrail, Thameslink, and electrification of the Great Western mainline along with lines in the north-west and Yorkshire.
But it also included new schemes, totalling £4.2bn, work on which will begin in 2014.
What will the money be spent on?
Much of it will be used to electrify parts of the network, reducing the UK's dependency on diesel-operated trains.
Where will it be spent?
Here's an overview of the new projects planned for each region of England and Wales.
(Note: railways in Scotland and Northern Ireland are the responsibility of the Scottish parliament and Northern Ireland assembly respectively)
£322m of track and capacity upgrades across Manchester and Liverpool.
A series of upgrades to the East Coast mainline from London to Leeds and Newcastle worth £240m, in order to create faster journeys and increase capacity.
The £800m electrification of the Midland main line between Sheffield and Bedford will mean full electrification between Sheffield and Chesterfield and London.
The line between Micklefield and Selby will also be electrified.
An £800m electrification and upgrade of the Midland mainline from Sheffield to Bedford, via Derby, Nottingham and Leicester, completing the electrification of the entire line between Sheffield and London.
Electrification of the line between Walsall and Rugely.
Over £700m to be spent on the most congested routes in London and the south-east region.
A new £500m rail link between Slough and Heathrow Airport was announced earlier this month. It will connect with the Great Western main line, meaning passengers travelling from south Wales, the west of England and the Thames valley will no longer need to travel to Heathrow via London. It is expected to be in operation by 2021.
More spending on the Great Western mainline, including more track capacity on the approaches to Bristol.
Extension of the electrification of the Great Western mainline from Cardiff to Swansea, costing £600m, plus full electrification of all the Welsh valley lines. The ongoing main line upgrade to Cardiff, costing more than £1bn, is due to be completed by 2017. Electrification of the London-Swansea line was first announced by the former Labour government in 2009. The upgrade to Cardiff was only confirmed last year.
How will these new projects be funded?
Mostly by above-inflation fare rises, which were announced in 2012.
In January 2012, fares went up by the rate of RPI inflation plus 1% on regulated fares. These are set to rise by RPI plus 3% in January 2013 and again in 2014.
Transport secretary Justine Greening told the BBC: "We've got to get the money from somewhere so, for the time being, the passengers are paying."
What else has the government said about the plans?
David Cameron called it the "biggest modernisation of our railways since the Victorian era". Nick Clegg said the plans would help "close the north south divide". Justine Greening added: "We all know that diesel is massively expensive so if we can move over to electric trains, not only are they greener, they're also cheaper and also they are lighter too, so what that means is that when they are on the track they don't damage it so much, so maintenance costs go down too."
How has Labour responded?
Shadow transport secretary Maria Eagle said: "We welcome this investment, it was actually first announced under the last Labour government... but this won't help jobs and growth now, as there's not going to be a penny spent until after 2014."
What about the reaction from passenger groups?
Anthony Smith, chief executive of the watchdog Passenger Focus, said passengers would welcome the "scale and ambition" of the investment, but added: "Value for money remains a concern. Passengers will want to see the government avoid above-inflation fare increases. These investments must be delivered in a cost-effective way."
And what about the new high-speed line between London and Birmingham?
It wasn't mentioned directly by either David Cameron or Nick Clegg during their press conference. However the department of transport's statement about the railway investment states: "We are building HS2".