Three spatial models relate urbanization, transportation and corridors:
- The location and accessibility model (A) considers an urban region as a hierarchy / order of services and functions and the corridor a structure organizing interactions within this hierarchy. The urban-system and central places theory mainly view cities as structurally independent entities that compete on overlapping market areas (also known as hinterland). Transport costs are considered a dominant factor in the spatial structure as the hinterland of each center is the outcome of the consumers’ ability to access its range of goods and services. Because of higher levels of accessibility along the corridor, market areas are smaller, and the extent of goods and services being offered is broader. Thus, market accessibility is the highest along the corridor.
- The specialization and interdependency model (B) considers that cities have a level of interaction and that transportation can be more than a factor of market accessibility, but also of regional specialization and comparative advantages. The Megalopolis concept introduced by Gottmann in 1961 underlines the creation of large urban corridors structured by transportation infrastructures and terminals. Accessibility and economies of scale, both in production and consumption, are factors supporting the development of such entities where urban areas are increasingly specialized and interdependent. The main assumption is that the accessibility provided by the corridor reinforces territorial specialization and interdependency along its main axis, and, consequently, the reliance on a regional transport system. However, the cost structure tends to be higher in metropolitan areas and along corridors servicing them. This provides an incentive for low added-value and land-consuming activities to locate the more peripheral areas.
- The distribution/flow model (C) considers that a major gateway of an urban region acts as the main interface between global, national, and regional systems. Under such a paradigm, three core structural elements define a regional corridor. The first are gateways regulating freight, passengers, and information flows, including flows at the international level, an issue that was not considered by the previous models. The second is transport corridors with a linear accumulation of transport infrastructures servicing a set of gateways. They provide for the physical capacity of distribution. The third are flows, their spatial structure, and the underlying activities of production, circulation, and consumption.