Spatial characteristics of transportation hubs: centrality and intermediacy

Centrality and intermediacy are identified in this article as spatial qualities that enhance the traffic levels of transportation hubs, and hence indicate which places are strategically located within transportation systems. The local, regional, national, continental or hemispheric centrality of a city has a fundamental impact on the city's own size and function and on its traffic-generating powers. Intermediacy, while it may reflect a natural geographical ‘in betweenness’, is a spatial quality that needs to be defined in the specific context of contemporary or prospective transportation systems and networks. Intermediate places can be given extra traffic if they are favoured by transport carriers as connecting hubs or relay points in the system. Passenger traffic data at US airports and container traffic at US and foreign seaports are used to illustrate these concepts of strategic commercial location. In many instances we are able to differentiate between true origin-destination and connecting traffic, giving a rough idea of the comparative contributions of the centrality and intermediacy factors to the traffic totals. It is no surprise that all large transportion hubs possess, at some scale and to some degree, both locational attributes — centrality and intermediacy.