A limb of one state’s territory cutting through another state, usually for access. The most famous is the Polish corridor (Howkins (2006) J. Transp. Geog. 4, 4). A corridor of commerce extends along a line of communication, such as the Mekong River (Furlong (2006) Pol. Geog. 25, 4), or the UK ‘M4 corridor’ (Coe and Townsend (1998) TIBG 23, 3).