A landslip between Haywards Heath and Brighton means trains are unable to run between these stations.
Disruption is expected until the end of the day.
Customer Advice
A reported landslip in the Hassocks - Burgess Hill area has been confirmed by Network Rail colleagues.
At this time, advice is to allow plenty of extra time for any journeys, or if possible, to delay travelling until later today when the situation is more stable.
Teams are working to assess what services can run, but you can expect a number of alterations to services.
There will be a limited number of trains able to run directly though to Brighton.
Services, where possible, will divert via Horsham and the West Coast, or via Lewes.
You can also expect services to terminate and restart earlier in their journeys, such as Haywards Heath or Three Bridges for example.
You will be able to use your ticket between Southern and Thameslink services, as well as METROBUS services between Brighton and Gatwick Airport.
Live departure boards can be found here.
You can view a live map of the network here.
You can also see an alternative route guide here.
Can you tell me more about the incident?
Currently, the information from the site of the landslip suggests that some repair works are needed before the line can reopen. Until these are done, it won't be possible to run all trains through the affected area.
Teams are working with Network Rail to ensure this is done as quickly and safely as possible.
Landslips can happen for a number of reasons, including severe weather. Areas at risk of landslips are monitored proactively to make sure the track is safe, and we also receive reports from train crews of any risks to the railway.
Check before you travel:
You can check your journey using the National Rail Enquiries real-time Journey Planner
Compensation:
You may be entitled to compensation if you experience a delay in completing your journey today. Please keep your train ticket and make a note of your journey, as both will be required to support any claim.