The paper will likely be launched on Tuesday against a backdrop of overcrowded carriages and above-inflation fare increases.

The UK's railways are nevertheless enjoying a boom as more and more travellers switch from cars and planes, due to congested roads and concerns about the environmental impact of flying.

"Thameslink is going to be approved," an industry source told Reuters on Friday. "That means tripling capacity from eight trains an hour to 24 trains an hour on the core route between Brighton and Bedford through London."

"You'll also get a rebuilt London Bridge station and a rebuilt Blackfriars station," said the source, adding the government would also approve the planned 500 million pounds reconstruction of Birmingham's New Street station.

London's urgent need to boost rail capacity was highlighted this week by the collapse of Metronet, which was handling a multi-billion-pound upgrade of the subway.

Rail consultant Malcolm Taylor of Faber Maunsell said he expected some word on the government's longterm plans for high speed rail in the UK.

"It won't be Japanese-style high speed trains at 350 kilometres per hour, but I suspect we'll see something about the slower Channel Tunnel-type high speed trains," he added.

PINCH POINT

Another industry source said Thameslink would be a priority project for the government.

"They'll be keen to get the first phase done ahead of the 2012 Olympics," the source added. "The east-west pinch point at Reading will also be addressed."

Easing congestion at Reading will help services from London's Paddington station, currently the worst performing in the country, as well as freight trains from the stone quarries in the Mendip hills to the west, said Chris Green of the Railway Forum.

"Reading is a colossal bottleneck -- the biggest in the country," he said, adding FirstGroup's First Great Western was seeing huge growth in commuter and intercity passengers on the route.

London's controversial Crossrail link, which would link towns to the west of London with others to the east, still needs parliamentary approval, so cannot be given the green light.

"But I'm sure they'll say some warm words about it," said one of the sources.

Taylor said Crossrail's main problem was finding the funding it needs, 8-9 billion pounds, which is almost double the government's entire yearly subsidy to rail.

"It's bound to feature in the plan because it would be so fundamental to life in London," he added.