The work, which includes double-tracking the line between Gretna and Annan, will be carried out by contractor Balfour Beatty Rail Projects Limited and is due for completion in February 2008. The upgrade will include re-decking of several bridges along the length of the line - Stonehouse road bridge, Bellevue Road bridge, and Stonehouse farm access bridge. New signalling and telecommunications systems will be installed and a new platform built at Gretna station.

Described by Network Rail as one of the single biggest improvements to the rail network in the Dumfries area for many years, the double tracked line is expected to cut delays and raises the possibility of shorter journey times and additional services in the future.

Ron McAulay, director Scotland for Network Rail said: "Gretna to Annan is an increasingly busy stretch of line in the Scottish rail network both for freight and passenger trains. Doubling the track will reduce delays and make passenger and freight trains faster and more efficient. Preparatory work has been progressing for the last 12 months and by summer 2007 we will have spent £35m on improving the rail network in the area, with benefits being widely felt."

The eight mile stretch between Gretna and Annan is an important passenger route from Carlisle via Dumfries to Ayrshire and on to Glasgow Central. It is also the main route for the transportation of coal from the freight terminal at Hunterston in North Ayrshire and the opencast sites in South Ayrshire to power stations in England. Increased line capacity will allow peak time freight transport to be accommodated with greater ease.

In addition, the double-tracked line will provide a new diversionary route for local trains on the Glasgow and South West route as well as for Virgin Pendolino trains traveling up the West Coast Main Line.