Network Rail has awarded three contracts worth £100m for the construction of the new Airdrie-Bathgate Rail Link.
An £80m contract to build new stations at Caldercruix, Armadale and Drumgelloch, and a range of other new structures and earthworks has been given to Carillion, a leading UK-based construction company.
BAM Nuttall has received a £14m contract to deliver a new station at Bathgate, a new platform at Airdrie and a range of bridge works and earthworks, while C Spencer will build the new light maintenance depot in Bathgate with the remaining £6m.
The contracts are part of £300m investment by the Scottish Government to add to the current three routes with four trains an hour in each direction.
Network Rail director for Scotland Ron McAulay said the link will provide enhanced accessibility and mobility to a growing population in the Central Belt and creating an additional rail link between the country's two largest cities.
The project will be complete by the third quarter of 2010, before reopening in December 2010.