South West Main Line

South Western Main Line
British Rail Class 444 with South West Trains livery at Poole railway station
Overview
Type	Commuter rail, Suburban rail
System	National Rail
Status	Operational
Locale	Greater London Surrey Hampshire Dorset South East England South West England
Termini	London Waterloo Weymouth
Operation
Opened	1838-1840
Owner	Network Rail
Operator(s)	South West Trains CrossCountry
Depot(s)	Clapham Junction Wimbledon Earlsfield Northam
Rolling stock	Class 444 "Desiro" Class 450 "Desiro" Class 455 Class 456 Class 220 "Voyager" Class 221 "Super Voyager"
Technical
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge
Electrification	750 V DC third rail
Operating speed	100 mph (160 km/h) maximum

The South Western Main Line (SWML) is a major British railway between London Waterloo and Weymouth on the south coast of England. A predominantly passenger line, it serves many commuter areas including suburbs of London such as around Hampton Court Palace and the conurbations based on Southampton and Bournemouth. It runs through Greater London, Surrey, Hampshire and Dorset.

It briefly runs alongside the Windsor and Reading Lines (the "Windsor lines") which terminate also at London Waterloo. It has many branches, including a line to Dorking, the three lines to Guildford one of which proceeds to Portsmouth and the West of England Main Line which spurs off after Basingstoke in Hampshire to terminate officially at Exeter. Together with these, it forms the core of the network built by the London and South Western Railway, today mostly operated by South West Trains. Network Rail refers to it as the South West Mainline.

Much of the line is relatively high-speed, with large stretches cleared for up to 100 mph (160 km/h) running. The London end of the line has as many as eight tracks plus the two Windsor Lines built separately, but this narrows to four south-west of Wimbledon, London and continues this way until Worting Junction west of Basingstoke, from which point most of the line is two tracks. A couple of miles from the Waterloo terminus, the line runs briefly alongside the Brighton Main Line west branch out of London Victoria, including through Clapham Junction – the busiest station in Europe by railway traffic. Tourist special services to a lesser frequency use the line such as the Cathedrals Express and the Alton terminus is a rail connection to a shorter heritage service, the Watercress Line.