Source: adapted from J.H. Ausubel, C. Marchetti, and P. Meyer (1998) “Toward green mobility: the evolution of transport”, European Review, Vol. 6, No. 2, pp. 137-156.
The growth of modal transport systems, as the case of the United States exemplifies, went through phases of growth, maturity, and decline. Growth usually involves massive investments in infrastructures, while maturity and decline often involve a rationalization of the modal network in terms of geographical coverage and level of service. There is also a substitution of passengers and freight from one mode to another, particularly when it involves higher speed, capacity, and efficiency. However, this does not necessarily mean that a prior mode will be abandoned altogether but that its growth potential is limited. A paradigm shift represents an event that marks a specific modal transport system prominence, often characterized by completing a significant infrastructure project that starts to impact economic and spatial systems. A peak year is when a modal system is about to reach maturity and experience a slow down in its growth.
The above figure provides a schematic representation of the modal developments in the United States from the 19th to the 21st century. The first concerns the canal system, which lasted 30 years (ΔT, the time it takes for the modal transport system to grow from 10% to 90% of its full extent) and peaked around 1836. Its paradigm shift took place in 1825 with the opening of the Erie Canal, and its maturity and decline were caused by the emergence of a more flexible and efficient inland transport system, rail. Rail took off in the latter part of the 19th century with the completion of the transcontinental railway in 1869, marking its paradigm shift. By the late 19th and early 20th centuries, most of the American territory was serviced by rail.
Road transportation emerged at the beginning of the 20th century, especially after the introduction of the Model T in 1913, the first mass-produced automobile. The growth of the road transport system marked the maturity and downfall of rail transport for passengers, especially for short and medium distances. The development of the Interstate Highway System marked the maturity of the road transport system as the national trade was increasingly taking place along major high capacity road corridors between major metropolitan areas, lessening the need for regional road construction. The latest wave of development is related to air transportation, which peaked around 2001 and is expected to last about 70 years. A key event that marked the dominance of air transport was the introduction of the Boeing 747 in 1969, which opened air travel to the masses since beforehand, air travel was mostly for the elite. The next transport technology is likely to be Maglev (Magnetic Levitation), but little is known about its potential impacts and which event would trigger a paradigm shift.