Major work for an ongoing £160m project to replace worn-out 1970s signalling will take place form Dec 25 until Jan 3.
During this period, no trains will run between East Croydon and London Victoria, with most trains diverted to London Bridge.
Rail bosses say it will bring 'greater reliability to passengers on the busy London Victoria to East Croydon route'.
Over 90 new signals will be erected, new points put in place, new train detection equipment installed along with upgrade power supplies and control moved to a state-of-the art control centre at Three Bridges.
Katie Frost, Sussex route Director, Network Rail, said:
“Nine days is a long time to close a main line railway and I know that a lot of people will be asking why we’ve got to do this now.
"The truth is that with fewer people travelling during the festive period this is still the best way for us to do large-scale improvements and if we had to do this work at weekends, we would be closing the railway far more often and disrupting far more people.
“So I’d like to that our passengers and neighbours for their patience with us, and urge people who are travelling over the festive season to plan their journeys before they leave.
“This project will have a huge impact on the reliability of the railway for years to come and it will be worth the wait.”
Chris Fowler, Customer Services Director for Southern, said:
“These engineering programmes are essential to give our customers the reliable, on-time services they rightly expect.
"We’re working closely with Network Rail and other transport partners to ensure our customers can get where they need to be when services are affected. Some journeys will take considerably longer than normal, so please check routes and times in advance.”
Over the 10-day closure, Pouparts Junction, an important stretch of railway near Battersea, will be completely rebuilt and signal gantries to house the signalling equipment, cables routes and power supply points will be installed along the lines from Balham to London Victoria.
By doing the work in a week-long chunks called “blockades” Network Rail can avoid the alternative of a long series of weekend or bank holiday closures over a number of years
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