Around 4,500 engieneers will put in more than 50,000 hours this Christmas and New Year on projects around Scotland.
Over the festive period, signalling and overhead power lines will be renewed and replaced at locations around Glasgow. New tracks will be laid on sections of the west coast main line and on the main line between Edinburgh and Glasgow - while a junction in Lanarkshire will also be renewed.
Rail bosses have said that the work is taking place when the network is 50 per cent quieter than usual.
Work on the electrification of the network will also continue with new overhead powerlines and supporting equipment being installed on sections of the Stirling-Alloa-Dunblane route and further progress being made on the upgrade of tracks and platforms at Edinburgh Waverley.
Engineers will also be working to refurbish and maintain bridges, level crossings and tracks elsewhere across Scotland during the holidays.
Across Britain, more than 32,000 railway staff will be out delivering £160m-worth of work creating more reliable infrastructure, reducing journey times and improving facilities and services for passengers.
Mark Carne, chief executive of Network Rail, said: “Thousands of passengers are on the cusp of seeing their rail journeys transformed in the months ahead as our massive £50bn Railway Upgrade Plan reaches its final stages with the introduction of thousands of new services now just around the corner.
“This Christmas will see over 30,000 dedicated and hardworking railway people working round the clock to deliver a bigger and better railway for the millions of people who rely on it every day.
“While most of the network is open for business as usual, some routes are heavily affected and so we strongly advise passengers to plan ahead this Christmas.
“We know that our railway is up to 50% quieter than usual during the festive period so taking on and delivering these huge transformational schemes at this time of year minimises our impact on passengers who, so research shows, understand the need for such activity.”
More than 95 per cent of the GB-wide network will be unaffected by the work, however, some routes will see significant changes to services.