Southern said that between Monday, December 1, and Friday, December 5, work will be taking place in the Earlswood and Salfords area, as well as between East Croydon and Oxted.
This means that some lines will be closed and will affect services travelling between London Victoria and Gatwick Airport, Brighton and Worthing, as well as between London Victoria and East Grinstead, Oxted and between London Bridge and Uckfield.
Lines between East Croydon and Oxted will be shut from 11.59pm from Monday, December 1, to Thursday, December 4.
This means that the 10.07pm London Bridge to Uckfield train will terminate at Oxted, with a replacement bus service running from Oxted to Crowborough and Uckfield.
The 11.53pm London Victoria to Oxted service will terminate at East Croydon, with a replacement bus service running from East Croydon to Oxted.
Journey times will be increased when using replacement buses.
Some lines in the Earlswood and Salfords area will be shut from 11.59pm from Monday, December 1, to Friday, December 5.
As a result, Southern said that trains will run to an amended timetable with extended journey times between London Victoria and East Croydon, and between East Croydon and Purley and Gatwick Airport.
Thameslink has said that from 10.45pm to 5.25am each night, no trains will call at Earlswood or Salfords.
Replacement buses will run between Redhill and Horley, and will call at Earlswood and Salfords.
