Construction of the mile-long path, alongside the A68 Edinburgh-Darlington road, started at the end of last month and will take around 12 weeks to complete.
Traffic lights are in operation from 7am to 5.30pm on weekdays while SB Contracts builds the path, from Earlston to Sorrowlessfield, on behalf of Scottish Borders Council.
Sustrans Scotland is picking up the £360,000 bill for the project.
The council’s executive member for roads and infrastructure, Selkirkshire councillor Gordon Edgar, said: “I am delighted this work is now getting under way, which will encourage more people to jump on their bike or pull on their walking shoes and get active.
“Sustrans Scotland specifically provides funding to ensure people across the country have access to safe walking and cycling routes, which this new shared path will do.
“There will inevitably be some disruption during the works for motorists, and we would advise motorists using the A68 regularly to give themselves a bit more time for their journeys.”
In a joint statement, Leaderdale and Melrose councillors Kevin Drum, Tom Miers and David Parker have welcomed the creation of the path, saying: “This cycleway-footway will provide local residents and visitors with a great facility which will allow them to link into the local paths network that has been developed by the Earlston Paths Group, thereby encouraging more people to get active and providing more opportunities for people to visit the local area.
“For many years, local residents, Earlston Community Council and Earlston Paths Group have campaigned to see this important link established, and we would like to pay tribute to the many people who have worked very hard to make this project a reality.
“Funding for the project is coming from Sustrans Scotland, and it is fantastic that £360,000 of external grant funding has been secured to deliver this project.”