The start of driver training marks the latest milestone for the Borders Railway, signalling the £350 million project is largely complete.
ScotRail will begin running its Class 158 trains, which are due to carry passengers from 6 September between Edinburgh and Tweedbank, south of Galashiels.
The training runs for the 60 drivers will involve some four return journeys a day.
The reopening of the northern third of the Waverley line to Carlisle – named after the Walter Scott novels – comes 46 years after it was shut in what was regarded as the most notorious of the Beeching cuts.
The closure of the line, which had opened in 1849, left the central Borders as the most remote area in Britain in terms of distance from a railway.
The 35-mile route will have seven new stations and includes an existing five-mile section to Newcraighall on the edge of the capital.
It will be the longest line yet to be reopened in Britain.
Network Rail, which is building the line for the Scottish Government, said the “core” railway was now complete, with remaining work including the stations.
Construction has been on time and budget, unlike the overall project, which is some £50m over budget and will be finished four years later than planned when it was approved by MSPs in 2006.
Passengers will enjoy the longest daily service on any line in Scotland, with trains running for almost 20 hours from 5:20am until nearly 1am.
A giant artwork will also be unveiled near the platforms at Waverley Station in Edinburgh to be used by Borders trains.
Project director Hugh Wark said: “The core engineering works have been completed, with the track and signalling needed to run trains now in place.
“We look forward to seeing driver training begin next week, and our engineers are continuing to work hard as we complete passenger facilities ahead of the line opening to the public.”
A ScotRail spokeswoman said: “This significant landmark brings us one step closer to the opening of the new line, something which is greatly anticipated by our staff and customers alike.”
Campaign for Borders Rail chairman Simon Walton, said: “Driver training is another tangible step on the way to bringing rail services back to the Borders, but also a tangible example of the social and economic opportunities the railway represents.
“Like those who will use the line, many of the staff are based in the Borders, bringing economic benefit to the region.”
David Spaven, rail consultant and author of Waverley Route: The battle for the Borders Railway, said: “It’s great to hear the start of driver training remains on schedule – this is another key milestone towards the reopening in early September.
“The level of interest being generated UK-wide by the Borders Railway is growing in leaps and bounds, and no wonder.”