The Grange Hill 'loop' is the circle of line at the east end of the Central Line, which doubles back on itself east of Leytonstone. Even simple moves such as shunts and straddles will have different effects to the same moves on a standard line. In fact, it is possible here to straddle to the same line. Successful players almost always require a good knowledge of Grange Hill loop workings.
(I think loops and the associated stations should be split into separate entries. - [SM])