A £1bn scheme to electrify the track between Edinburgh and Glasgow is to be funded by Network Rail.
The company has agreed in principle to borrow money against the value of its assets.
The Edinburgh Glasgow Improvement Programme (EGIP) could cut journey times between the two cities to around 35 minutes allowing 13 services an hour.
A Network Rail spokesperson said: "Transport Scotland has asked Network Rail to use our Regulatory Asset Base to facilitate the funding of the Edinburgh-Glasgow Improvement Programme.
"This project has wide-ranging benefits for communities across the central belt of Scotland and we look forward to playing our role in delivering this ambitious programme."
The programme includes the electrification of the Dunblane and Cumbernauld lines.
In addition a new rail and tram interchange station at Gogar will be created.
The project is due for completion in 2016.
Scottish Government spokeswoman said further announcements will be made in due course: "The Scottish Government has ambitious plans for improving the country's rail network and is delivering the biggest transport construction programme seen in Scotland in a generation."
(GK/KMcA)
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