From December 10 there will be additional stops at Newhaven Harbour, Glynde and Berwick train stations.
On the Brighton to Seaford line there will be additional weekday stops introduced to create an hourly service all day, which is increased to half-hourly at peak times. Currently, it is only served broadly at peak times, until 09:00 and between 16:00 and 19:00.
There are also additional stops being introduced for Glynde and Berwick stations on the last train from Brighton to Eastbourne from Monday to Saturday
This currently departs Brighton at 23:32 and means that the last train of an evening from Brighton to Glynde and Berwick will no longer be the 21:56 departure.
Maria Caulfield MP said: “I very much welcome the improvements that Southern are making to train services in the local area, I have long been a campaigner on improving rail links across the constituency. I know that this latest improvement will be welcomed by residents.