The Arun Valley line, also known as the Mid Sussex line, is part of the Southern- and Thameslink-operated railway services. For the initial part of the route trains follow the Brighton Main Line, and at a junction south of Three Bridges the route turns westwards. It then runs via Crawley, Horsham and Arundel, before meeting the West Coastway line at Arundel Junction. Trains on the Arun Valley line then mostly proceed to either Bognor Regis or Portsmouth Harbour, with an additional peak hour service which first proceeds to Littlehampton, and subsequently to Bognor Regis.