Stouffer (1940) Am. Soc. Rev. 5, 6 argues that the spatial distribution of competing (alternative) intervening destinations influences decision-makers’ choices (Cascetta et al. (2007) Papers Reg. Sci. 86, 4). See Alix et al. (1999) J. Transp. Geog. 7, 3 on Montreal as an intervening transhipment opportunity between Quebec and Europe.