Network Rail said the Borders railway project is now entering the main phase of track-laying on the route.
Transport Minister Keith Brown and Mark Carne, chief executive of Network Rail, visited the newly-constructed Shawfair station to launch the latest phase of the scheme.
By the end of the year, a state-of-the-art rail installation machine, capable of laying over 1km of track per day, will complete the Borders route. The machine, operated by main contractor BAM, will install rails on to 90,000 sleepers already laid out along the way.
The project will re-establish passenger services for the first time in over 40 years from Edinburgh through Midlothian to Tweedbank.