Source: Adapted from Rodrigue, J-P, C. Comtois and B. Slack (1997) “Transportation and Spatial Cycles: Evidence from Maritime Systems”, Journal of Transport Geography, Vol. 5, No. 2, pp. 87-98.
Since transportation technology is widely standardized, cycles represent different scales of spatial change of a transport system. However, some transportation systems have limited potential for spatial diffusion simply because of their operational scale and the nature of the markets they service. A public transit system covers at most a metropolitan area and cannot be expanded further. Transport development and spatial diffusion are closely linked. The growth and contraction of transport systems are commonly taking place through a hierarchical diffusion process influenced by the existing network structure. As highly dynamic entities, networks are the agents and, at the same time, the recipients of spatial diffusion.
The above figure provides a synthetic representation of a cycle impacting two transport systems, one which is local in character and the other that is transborder in nature. Cycle C1 represents the diffusion of a transit system closely related to urban growth, but also with competition from other modes. From A to B, cycle C1 experiences periods of introduction, growth, and maturity, while after B, there is a potential for obsolescence and competition causing a decline in ridership. Devolution has been the fate of public transit in several North American cities since the 1960s. Cycle C2 is more indicative of a transport system servicing international trade, like container shipping. With an initial state affecting a service area of limited geographical coverage (a few ports; C), growth and maturity provide a transportation system covering a global scale and often taking shape of a hub-and-spoke network to minimize operation costs while maintaining a good market (spatial) coverage (D). Transport systems enter a phase of decline and eventually obsolescence only if they cease to have a commercial utility.