The work will affect trains on Saturday and Sunday (March 22 and March 23).
We have compiled the details for you to plan your journey this weekend.
Saturday and Sunday (March 22 and March 23):
Engineering work is taking place between Three Bridges and Horsham, closing all lines.
Buses will replace trains between Three Bridges and Horsham.
Trains will run between Horsham and Bognor Regis.
Trains between London Victoria and Portsmouth Harbour will run to an amended timetable with extended journey times and will be diverted via Hove.
Sunday (March 23):
Replacement buses will run between Sutton and Epsom and Dorking on Sunday.
Trains will also run to an amended timetable between East Croydon and Purley.
Trains between London Victoria and Reigate will be amended to run between Redhill and Reigate only.
Passengers should change at Redhill for alternative Southern services between Redhill and London.
Engineering work is taking place between Purley and Gatwick Airport, closing all lines via Redhill early on Sunday morning.
Before approximately 7am, trains that usually run via Redhill will be diverted to run on alternative lines.
Replacement buses will run between East Croydon and Redhill and Horley.
