RAIL services westbound have been halted after a passenger was taken ill at Shoreham.
Southern Rail reported the incident just after 10am and said the westbound lines, from Brighton and London to Worthing and Littlehampton, were currently blocked.
Trains into Hove and Brighton are also delayed.
A spokesman said: “A passengers has been taken ill on board a train at Shoreham and this is causing delays of up to 20 minutes to trains between Worthing and Hove/Brighton.”