Gateways and Hubs
Gateways and hubs are locations where flows converge and the foremost expression of global connectivity. However, they differ in terms of the nature of their connectivity. While a hub is a central location in a transport system with many inbound and outbound connections of the same mode, a gateway commonly implies a shift from one mode to the other (such as maritime / land). A gateway is performing an intermodal function (between modes) while a hub is mostly transmodal (within a mode). Transport corridors are commonly linking gateways to their hinterland. Gateways tend to have a temporal stability as they often have emerged at the convergence of inland transport systems and through the long term accumulation of infrastructure and investments.
The importance of a hub can change rapidly based upon the commercial strategies of its users. For instance, a transport company (e.g. maritime shipping or air carrier) may decide to switch form one hub to another if it improves its operations or commercial opportunities. Flows, origins, destination and the modes used can therefore change. In this context, a hub can lose a share of its connectivity as the network it is part of is reorganized, which is rather common in the airline industry. The functions of gateway or hub are not mutually exclusive since a location can assume both functions if it fits the commercial strategies of carriers.
The functions of centrality and intermediacy are particularly relevant to the emergence of a global nodal space since centrality focuses on nodes as an origin or destination of flows while intermediacy focuses on nodes as intermediate locations where transshipment is performed. While central locations obviously correspond to large metropolitan areas, intermediate locations have developed a rather unique geography where the importance of a location is more derived from its relative accessibility (in terms of other locations) than its intrinsic characteristics.