The work is set to impact the route until 10.59pm tomorrow (Sunday), according to a statement from Southern Rail.
It added that engineering work is taking place between Chichester and Ford, closing all lines, the routes affected are: Great Western Railway between Great Malvern / Cardiff Central / Bristol Temple Meads / Romsey / Southampton Central and Brighton Southern between Southampton Central / Portsmouth Harbour / West Worthing and Brighton / Haywards Heath / London Victoria
And engineering work in the Romsey area tomorrow morning will see the 8.19am Romsey to Brighton start from Southampton Central with a 7.55am bus replacement from Romsey to Southampton Central.
As a result Great Western Railway services to / from Brighton will terminate / start from Chichester. Replacement buses will run between Chichester and Littlehampton to connect with Southern services to / from Brighton.
On Southern, trains will not run between Chichester and Barnham. Buses will replace trains between Chichester and Barnham / Littlehampton and buses will also replace trains on the Bognor Regis branch between Bognor Regis and Barnham.
On Saturday, trains which usually run between London and Portsmouth / Southampton Central / Bognor Regis will be diverted to Littlehampton. On Sunday, trains on these routes will not run. However customers can use South Western Railway services between Southampton Central and Havant all weekend.
It is advised to check before you travel using the National Rail Enquiries Journey Planner and noting that non folding bicycles are not allowed on rail replacement bus services at any time. Folding bicycles are allowed if fully folded.
For more information on the work, click HERE