Rail passengers face delays between Horsham and Barnham until Friday (July 13) due to a signalling problem.
Yesterday morning, Southern were advised by Network Rail of a fault with a signal at Arundel station.
Engineers have attended the site and identified the fault.
However, due to the extensive nature of the work, it will take a number of days to repair without causing extensive impact to the train service.
As a result, trains travelling from Horsham towards the coast will have to stop at the affected signal at Arundel station and get verbal confirmation from the signaller before proceeding.
This can add up to five to 10 minutes to a trains journey.