The railway line between Eastleigh and Fareham will be shut until tomorrow (Sunday 3 July) while essential maintenance is carried out.
Passengers travelling between Portsmouth Harbour and London Waterloo via Basingstoke will be affected.
It's part of a nine-day closure running from Saturday 25th June to Sunday 3 July.
Engineers are installing retaining walls and fixing the slope and the cuttings outside a tunnel in Fareham, which has experienced failures in the last few years.
In 2016, Storm Frank's extreme weather meant temporary repairs had to be made, but the area now needs a permanent fix to keep trains running safely.
An inspection or the track, signalling and drainage systems in the area will also take place.
Replacement buses will be running between Eastleigh and Fareham during the closure.
South Western Railway services between London Waterloo and Portsmouth Harbour via Basingstoke will start and terminate at Eastleigh and Fareham.
On Sunday 3 July, some Great Western Railway trains and Southern services will be diverted via Netley and Swanwick.
Passengers being are advised to check their journeys before they travel.