During the next two weekends, engineers will be working to replace two miles of track at various locations around Cove Bay, Montrose, and Arbroath.
Network Rail teams will be removing the old track before laying new stone ballast, sleepers, and rails.
Due to the complexity of the engineering work, these projects cannot be delivered without some short-term closures of the line.
Passengers are being urged to check their journey before travelling and more information on the changes to services over these weekends can be found on www.nationalrail.co.uk, or individual operators’ websites.
Liam Sumpter, Network Rail route director for Scotland, said: “Our engineers will be working around-the-clock to complete these projects as quickly as possible.
“Helping to make our infrastructure more resilient and more reliable, the work we are doing is part of a five-year, £4bn investment in our railway.
"However, such complex improvement work cannot be delivered without some short-term disruption of the railway and we’re urging passengers to plan ahead and check their journey in advance.”
Network Rail owns, operates and develops Britain's railway infrastructure - 20,000 miles of track, 30,000 bridges, tunnels and viaducts and the thousands of signals, level crossings and stations.
It runs 20 of the UK's largest stations while all the others, over 2,500, are run by the country's train operating companies.
Usually, there are almost five million journeys made in the UK and over 600 freight trains run on the network.
People depend on Britain's railway for their daily commute, to visit friends and loved ones and to get them home safe every day.
The company manages and delivers thousands of projects every year to respond to growth and demand the railway has experienced - a doubling of passenger journeys over the past 20 years.