Outer South London Line

The Outer South London Line is an unofficial name for the rail service in south London from Victoria to London Bridge via Gipsy Hill, operated by Southern. It is 16 miles (25.7 km) long and runs over the West End of London and Crystal Palace Railway between Balham and Crystal Palace to connect the two London branches of the Brighton Main Line. "Outer" distinguishes it from the official South London Line, which runs via Peckham Rye.

See also Inner South London Line

More information on the Wikipedia page.