A replacement bus service has been laid on between Horsham and Three Bridges after a person was hit by a train in Crawley.
Rail operator Southern has warned passengers to add up to 60 minutes to their journey times.
A spokesman said the replacement buses would run between Barnham and Horsham and also between Horsham and Three Bridges.
Some trains which usually travel via Horsham / Crawley will be diverted via Brighton and not call at stations between Ford and Three Bridges.
Passengers may use their tickets on the following operators:
First Capital Connect on reasonable routes
First Great Western between Redhill and Guildford
London Buses between Redhill and Croydon
London Underground on reasonable routes
Metrobus between Horsham and Three Bridges / Redhill
Southeastern on reasonable routes
South West Trains between Portsmouth and London Waterloo
Replacement buses have been requested to run between Barnham / Horsham and Three Bridges but there is no estimate for when these will be available.
A spokesman for Southern said: “Services resumed going on the Horsham to Three Bridges line at just after 11.20am.
“We’re looking at getting the rest of the line going but that will depend on the investigations.
“There was some damage to the train which is why it’s still there.”
Police, firefighters, the Kent, Surrey and Sussex Air Ambulance and paramedics were called to the Horsham Road level crossing, in West Green, shortly before 10am today (September 5).
A spokesman for the South East Coast Ambulance Service said: “Sadly we were unable to help the person who was pronounced dead at the scene.”