Southern has confirmed train lines between Barnham and Brighton are reopened in both ways due to an earlier signalling fault at Angmering (February 7).
Train services are still expected to be delayed by up to 20 minutes, Southern has warned.
Southern also said some services are likely to be revised.
A rail replacement bus service is expected to operate from Barnham, Worthing and Angmering with an estimated start time of 12.30pm. This service is due to be in place until 2pm.