People travelling by train in West Sussex are advised to expect significant delays after a major signalling failure this afternoon.
Southern said trains running between Ford and Southampton Central may be cancelled or delayed until 6pm.
Services are currently unable to run between Chichester and Barnham, also affecting routes to and from Horsham and Littlehampton.
A spokesman said: "Southern have been advised that a number of location across the west coast experienced power failure to the signalling system, as a result services in the immediate areas came to a stand as a safety precaution.
"Network Rail have managed to restore power in some areas, however Southern are unable to run any services past Barnham in the Portsmouth / Southampton direction.
In a post on social media, the rail provider said ticket acceptance has been arranged for a number of Stagecoach, Compass Travel and Metrobus routes (see above).