Victoria line
For many years there have been proposals to extend southwards from Brixton one stop to Herne Hill. Herne Hill is a railway station that can link passengers to Kent and other places. The tube station would be on a large reversing loop with one platform. This would remove a problem of having too many trains by getting rid if the need for trains to reverse at Brixton. However, this would cost too much money for how little it would actually help passengers.  Given that the line is very overcrowded, this is the only extension that could ever happen.