Southern has said that it is unable to provide a train service to and from Chichester for the rest of the day (Monday).
Trains have been unable to run between Chichester and Barnham all day due to a fault with the signalling system. Read more here
Providing an update on Twitter at 2.30pm, Southern wrote: "We're unable to provide a train service to and from Chichester today.
"We are running a replacement bus service that will operate every 15 minutes between Barnham and Chichester. Disruption between the two stations is expected until the end of the day."
Meanwhile, Network Rail Kent and Sussex said engineers are working to resolve this issue 'as soon as possible'. It added: "Please bear with us."
Southern said 'multiple signalling issues' were discovered during planned engineering work in the Barnham area this week, and were traced back to a faulty cable.
It said engineers had found the fault with the equipment and 'are now working on fixing the issues'.
Today's issues on the railway coincide with the major, nine-day West Coastway engineering project, to allow for 2.3km of new track to be laid and improvement works at several level crossings.
During the weekdays, from Monday, October 28 to Friday, November 1, buses will replace trains between Havant and Chichester. On the weekend dates, the line between Havant and Barnham will be closed, meaning buses will replace trains between those stations on each date affected.
Due to today's signalling problems, replacement buses have been in operation between Barnham and Chichester, as well as between Chichester and Havant.