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 (where there is a junction with the Portsmouth Line) and Arundel, before meeting the West Coastway line at Arundel Junction. Trains on the Arun Valley line then proceed to either Bognor Regis, Portsmouth Harbour or Southampon Central Many stations on this line retain the short platforms which were originally built, not being extended by the Southern Railway when the line was modernised in the 1930s. This causes operational difficulties to this day, which require frequent platform and on-train announcements, telling passengers they must travel in the correct part of the train. History The line was opened in three stages by the London, Brighton and South Coast Railway (LB&SCR) between 1848 and 1863, creating what was then known as Mid-Sussex route to Portsmouth. Three Bridges–Horsham A single track branch line was opened on 14 February 1848, with passing places at the intermediate stations at Crawley and Faygate. The line was doubled throughout in 1862. The stations now at Ifield and Littlehaven were not opened with the line, both being opened on 1 June 1907: Ifield as Lyons Crossing Halt and Littlehaven as Rusper Road Halt; both serving the outskirts of their nearby towns. An additional stop was opened at Roffey Road Halt', however this station was closed in the 1937, as the land next to the station had remained undeveloped. Horsham–Pulborough The Midhurst Railways line from Horsham to Pulborough, Petworth and Midhurst was opened on 10 October 1859. The section from Hardham Junction to Midhurst was closed between 1964 and 1966. The Steyning Line from Horsham to Shoreham by Sea was opened on 1 July 1861 branching off at Itchingfield Junction south of Horsham. It closed in 1966. Pulborough–Arundel The line between Hardham Junction south of Pulborough, and Arundel Junction on the coast line via Arundel was finally opened on 3 August 1863 creating a through route to Portsmouth. Originally, the main LB&SCR route from London to Portsmouth used the Portsmouth line to reach Horsham. However, with the increase in demand at Gatwick Airport, the mainline services were re-routed in 1978 to serve the airport and then travel via Three