London Underground ticketing destinations and most interchange stations are in zone 1, meaning that most journeys over similar distances will cost the same. A few stations in the north east of the network, on the Central line, outside Greater London (in the Epping Forest district) are in zones 4, 5 and 6. In the north west of the network, on the Metropolitan line, zones 7, 8 and 9 (formerly A - D) cover stations outside Greater London including Amersham and Chesham in the Chiltern district of Buckinghamshire. Unlike the lower numbered zones, these ancillary areas do not encircle the capital. Some stations are
M25 motorway from in Potters Bar to in Byfleet. Three Greater London boroughs (Enfield, Hillingdon and Havering) have realigned their boundaries to the M25 for minor stretches; while in others, most notably in Essex and Surrey, the radial gap between Greater London and the motorway reaches , neither of which coincide with the Metropolitan Green Belt. Major towns listed as destinations (right), in various counties, adjoin the M25. North Ockendon is the only settlement of Greater London situated outside the M25. In 2004, following an opinion poll, the London Assembly mooted for consultation alignment of the Greater London boundary with the M25.