Southern Rail is warning passengers that trains could be delayed due to an earlier points failure.
Trains were left unable to run either northbound or southbound at Billingshurst due to a points failure which has now been fixed, Southern Rail said.
The failure, south of the station, affected trains between London Victoria and Barnham, Bognor Regis, Portsmouth Harbour and Southampton Central.
Although both lines have now reopened Southern warned customers of delays of up to 20 minutes and alterations to services.
Disruption is expected to continue until 5.30pm.