Author: Dr. Jean-Paul Rodrigue
The mega-urban region is a complex regional entity articulated along transport corridors linking a series of metropolitan areas.
1. Large Scale Urbanization and the Mega Region
Globalization, urbanization, and the emergence of urban regions are intractably linked. Up to the 20th century, several factors prevented the setting of large cities above 1 million inhabitants, and even more so of urban regions. One of the most salient constraints was the technical inability to support the large volume of people and merchandise flows such an entity would generate, particularly food supply. Prior to 1950, only two cities surpassed 8 million inhabitants; New York and London. Thus, large-scale urbanization is a process that began or at least started to be acknowledged after World War II when the global urban population entered a phase of accelerated growth and when new technical means became available. Through a series of stages, motorization, particularly the diffusion of the automobile, the construction of highway systems, and regional air transport networks, all favored the geographical expansion of the urban real. Despite its spatial diffusion, urbanization was able to maintain a level of cohesion with increased interactions. The distribution of urban-related activities over a large territory created a new transactional space and a new frame of reference for what could be considered urban. The result was a fundamental change in the spatial structure of what can be considered a city at the global, regional, and local scales:
- Globally, a complex network of gateways is interacting in a system of flows of people, freight, and information, composing spheres of production, consumption, and circulation. Conventionally, urbanization is considered the outcome of socioeconomic processes occurring nationally, but global economic processes are among the strongest forces shaping contemporary urbanization. This has been accompanied by expanded forms of global mobilities, including migration, business travel, and leisure. Distribution networks have expanded, namely through the division of production, manufacturing, and consumption. This has been accompanied by a growth in the quantity of freight being shipped and more complex supply and distribution chains. These are derived from strategic considerations where issues such as production and subcontracting planning and the choice of hubs and routes are considered for implementing global supply chains.
- Locally, the urban structure of most cities has evolved from a nodal single-center structure to a multi-nodal one, with suburbanization being the dominant paradigm. Additional demands for space and lower locational costs have been leading forces behind this process. This has often resulted in a fragmented system of movements and a complex lattice of interactions within a metropolitan area. Many activities related to freight distribution have been impacted by the construction of new transport terminals and distribution centers in response to growing space requirements as well as from the imperatives of fragmented supply chains. From their traditional location around central areas with prevalent port and rail linkages, transport terminals, and distribution centers have shifted to peripheral locations where road and airport linkages are more predominant.
- Regionally, a functional specialization of interconnected urban centers has emerged with a division of economic activities regulated by hubs and regional transport infrastructures. The prevailing spatial structure of regional accumulation and distribution is thus articulated by a corridor dotted by major urban centers.
The regionalism of urbanization implies that some cities have become metropolitan areas, but that individually or as a group, they have become a complex functional regional entity, the mega-region. It is the outcome of a historical process of urban expansion and interconnection, as a mega-region cannot exist without an underlying urban system that defines its structure and interactions. However, the term mega-region requires some nuances because of the size and spatial scale it may take and because it usually does not discern between single and multiple metropolitan areas regions. They are dynamic entities linked with economic, infrastructural, and technological processes. Three scales can therefore be suggested to describe the mega-region:
- Metropolitan Area. A single large city is often officially defined and named a jurisdictional and statistical unit that functions as a labor, consumption, and production market. It can be considered as the basic economic unit of the global economy. The metropolitan area is not necessarily continuously developed and can include rural, non-urban (when there is no agriculture), or discontinuous urban development areas. Although a metropolitan area is composed of multiple jurisdictions, it is structured by the commuting range of the core city, from which radiates highways and urban transit lines.
- Extended Metropolitan Region (EMR). A continuum of urban activities, often interwoven with rural activities, that includes a large urban agglomeration (several million) and a network of secondary (satellite) cities. It combines many different economic activities and land uses, including agricultural activities, large-scale housing projects, and industrial estates. The EMR usually extends beyond the standard definition of a metropolitan area to include rural areas.
- Mega-Urban Region (MUR). A large-scale corridor is composed of several metropolitan areas (some of which are EMRs) structured by transportation infrastructures and terminals supporting an intense system of regional economic and social interactions. The term megalopolis has also been used to characterize such an entity spanning several hundreds of kilometers. MURs also have a substantial rural population, but agricultural activities are highly conditioned by the proximity of large urban markets. Although there is no formal convention about the minimum size, MURs have at least 10 million inhabitants, mostly concentrated in a few large multimillion metropolitan areas (or EMR). The MUR is a specialized and interdependent entity that acts as a comprehensive system of production, consumption, and distribution. It serves as the main gateway between global, national, and regional systems of accumulation and distribution.
Urban regions form an extended but cohesive territory, creating a new transactional and circulation space that has become a global competitive unit internally and externally. Internally, the vast accessible market it confers incites competing firms to service the urban region with goods and services efficiently. Externally, the mega-region becomes a more efficient production unit because of its economic, innovative, and labor potential coupled with access to global markets through large-scale transport terminals. A share of the competitiveness of an urban region can thus be attributed to its transport infrastructure that supports its internal flows as well as its relations with external markets.
2. The Structure and Articulation of Mega-Urban Regions
The emergence of mega-urban regions as a distinct spatial structure began to be acknowledged in the 1950s as they appeared in the developed world, namely in North America, Western Europe, and Japan. More recently mega urban regions have emerged in the developing world, particularly in East Asia. Megaregions have become a common pattern of global urbanization, which reflects a homogenization of infrastructure, production, and consumption. The structure of mega-urban regions can be better understood through the concepts of articulation nodes, corridors, and flows:
- Articulations nodes are where the organization and regulation of passenger transportation and freight distribution are taking place through a set of terminals and related added-value activities. As hubs or gateways, they provide an interface between global and regional flows and are built upon the convergence of transport networks.
- Corridors with a linear accumulation of transport infrastructures servicing a set of articulation nodes. They support by their physical capacity the mobility of passengers and freight. Corridors usually emerge in phases of infrastructure and economic development, creating an increasingly interconnected region.
- Flows are the expression of work, production, distribution, consumption, and social activities. An urban region has a complex web of flows ranging from metropolitan commuting ranges to intermodal flows connecting the market of an urban region to global supply chains.
An articulation node is a concrete geographical node within a wide variety of transport chains servicing global and regional transport systems. It involves a concentration of transport terminals, each hub servicing its respective transport chain. The hierarchy and sequence of global, regional, and local mobility are reflected in the hierarchy and sequence of articulation nodes. The importance of an articulation node is measured by the volume and the nature of the traffic it handles and the geographical extent of the mobility it supports. For instance, an international articulation node (gateway) handles a substantial amount of maritime, land, and air traffic and has a hinterland that encompasses several regional articulation nodes. The world’s largest articulation nodes are usually the anchor points of large urban regions. A regional articulation node will handle traffic mostly related to land transportation and will be characterized by a smaller hinterland. For urban regions, freight articulation nodes are particularly important in shaping their dynamics and spatial structure through three functions:
- Freight Transshipment. Involves a set of intermodal activities transshipping freight from one mode to the other. Dominant articulation nodes handle substantial amounts of freight through their transport terminals. This function is particularly important for gateways providing an interface between urban regions and the global economy.
- Freight Integration. Involves activities related to the logistics of freight circulation, the most common being the composition, warehousing, and decomposition of freight shipments. Distribution centers are the common expression of this function of articulation, often linked with transshipment activities taking place at major terminals. It underlines the role of the articulation node as a distribution platform for the urban region.
- Freight Transit. Involves freight flows bound to another location but transiting through an articulation node because of its intermediacy within a regional transport network.
A commonality of many mega-urban regions is their orientation and development along corridors where transport, economic, and demographic processes are linearly articulated and integrated. Corridors offer better accessibility and connectivity and have consequently shaped urbanization in many parts of the world. This involves three dimensions:
- A mega-urban region is considered to be a hierarchy of functions, and the corridor is a structure organizing interactions within this hierarchy, from large metropolitan areas to small satellite towns.
- Cities can have a level of interaction and transportation could be more than a factor of market accessibility, but also of regional specialization and comparative advantages. 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.
- The mega-urban region is a system of flows reflecting local, regional, and global passenger and freight mobilities. The corridor is the structure regulating these flows.
While passenger flows are derived from economic and social interactions, freight flows are dominantly derived not only from the location of production and consumption activities but from the complex web of intermediate activities, such as warehousing and transshipment. Combined, they form a regional transactional space in which many actors in the supply chain, from producers to consumers, interact. These elements place the emphasis on the intermodal capacity of hub centers having an interface with multimodal transportation systems as well as with the logistical management of this complex distribution system where the local is integrated with the global. The corridor is then a sequence of distribution activities supporting a vast array of functions within the urban region; a logistically integrated axis.
3. Modal Corridors in Mega Urban Regions
The mega-urban region is interfacing with the global economy mainly through its port and airport terminals and regionally organized through modal corridors including road, rail, and on some occasion, fluvial systems:
- The maritime corridor operates at a scale that is very different than those of land-based modes and usually does not play an important role in the internal structure of urban regions, with the exception of those along a coastal area serviced by short sea shipping (e.g. Tokaido). Maritime corridors are structured by the integration of port cities (maritime services and transshipment functions) into port systems (maritime distribution functions), forming a global trade network. Containerization has particularly impacted maritime corridors with the emergence of global maritime trade routes servicing the world’s largest markets (urban regions). However, the growth in the size of ships tends to favor the concentration of traffic at large gateways, which is shaping the development of maritime shipping networks.
- The fluvial / coastal corridor corresponds to waterways linking markets, industrial areas, and resource-producing regions. For many urban regions, the fluvial corridor is the main defining spatial structure (e.g. Shanghai-Nanjing, Pearl River Delta, Rhine / Scheldt Delta) as it historically the river was the main trade corridor. This support is relatively less important in the current context, but the structuring effect of the fluvial corridor created a spatial structure that was reinforced with land corridors. Other urban regions are structured along a coastline (e.g. BostWash, Tokaido, Southern California) as they initially emerged as a system of independent port cities that eventually became interconnected through land corridors.
- Land corridors can be divided into two modes having separate but often integrated logistics; road and rail. Land transportation infrastructures are the core contemporary element structuring mega urban regions, mostly by connecting major articulation nodes. Rail corridors and highway systems have a strong spatial imprint in shaping corridors, a force that has been more recently reinforced by the setting of high-speed rail systems. However, the structuring effects of rail vary because mega-urban regions have a different modal split between passenger and freight rail.
- Air corridors have lesser structuring effects because they were more recently established (particularly in developing countries) and concern smaller volumes than their road and rail counterparts. Due to the shorter distances within the mega-urban region, regional air transportation involves only the largest urban centers. Yet, the development of high-frequency air shuttles is salient between large city pairs in relative proximity (300 kilometers or more), but also with smaller centers large enough to justify services. Thus, air traffic within mega urban regions can be extensive since it is related to business interactions and the demand has steadily risen. However, the development of high-speed train networks has been able to successfully compete with air corridors in several mega-urban regions, such as in Europe, Japan, South Korea, and China.
Corridors have become the object of intense modal competition with the growth of movements of passengers and freight. For passengers, highways, (high speed) rail and air transportation respectively have a market share that is a function of the distances involved, the capacity of the corridors, cost, and convenience. Conventionally, freight flows within corridors tended to be fragmented and segmented since each mode tried to exploit its own advantages in terms of cost, service, reliability, and safety. In many cases, trucking benefited, taking a significant share of regional freight transportation. More recently, as congestion increased along corridors and as productivity and efficiency improvements were sought within supply chains, modal complementarity improved. Because of the intensity of the interactions they support and their concentration along corridors congestion, delays and pollution are common externalities associated with mega urban regions.
Corridors represent a setting where integrated transport systems are particularly suitable to improve the mobility of passengers and freight. As either distance or congestion increases, the efficiency of road transportation along corridors is challenged. Improvements can be achieved by shifting passengers and freight to other modes that are less congested or by using existing modes in a combination where they are respectively the most efficient. The later opens opportunities for freight diversion where a terminal located along the corridor is used to transfer freight to a mode that lessens congestion inbound or outbound a metropolitan area. Such strategies are already been used by distributors that are opting for a strategic location along a corridor to service a whole urban region.
The mega-urban region has become a fundamental component of the global economy since they account for a large account of production and consumption. While their development appears to have peaked in developed economies (a process linked with their demographic profiles), the developing world will continue to see the emergence of regional urbanization structures that will condition future investment in transport infrastructure along corridors.
