Author: Dr. Jean-Paul Rodrigue
The physical environment imposes major constraints on transportation systems, in terms of what mode can be used, the extent of the service, its costs, capacity, and reliability.
1. Physical Constraints
Since transportation involves a set of technologies designed to overcome the constraints of space, particularly distance, physical constraints are the most fundamental to consider. Even if technological improvements have made the physical constraints of space less acute, they still play a considerable role in the location, path, construction and maintenance costs, and operational conditions of transportation systems.
Features such as mountains and valleys have strongly influenced the structure of transportation networks, the cost, and the feasibility of transportation projects. Land transport infrastructures are usually built where there are the least physical impediments, such as on plains, along valleys, through mountain passes, or, when necessary, through digging tunnels. When the first alpine tunnels began to be built in the 19th century, they were constructed at higher altitudes to make their length shorter but more difficult to access. By the mid-20th century, boring technology allowed the construction of base tunnels. Water depths and the location of obstacles such as reefs influence water transport. Coastlines exert an influence on the location of port infrastructure. Aircraft require airfields of considerable size for take-off and landing. Topography can impose a natural convergence of routes that will create a certain degree of centrality. It may help a location become a trade center as a collector and distributor of goods.
Topography can complicate, postpone, or prevent transport activities and investment. Physical constraints fundamentally act as absolute and relative barriers to movements. An absolute barrier is a geographical feature that entirely prevents a movement, while relative barriers impose additional costs and delays. The topography notably influences land transportation networks, as highways and railways tend to be impeded by grades higher than 3% and 1%, respectively. Under such circumstances, land transportation tends to be denser in areas with limited topography.
The properties, distribution, and circulation of water play an important role in the transport industry as hydrology is at the same time supporting and constraining transport activities. Maritime transport is influenced by the availability of navigable channels through oceans, rivers, lakes, and shallow seas. Several river systems, such as the Mississippi, the St. Lawrence, the Rhine, the Mekong, and the Yangtze, are important navigable routes into the heart of continents. Historically, they have been the focus of human activities that have taken advantage of their transport opportunities. While Europe, the Americas, and East Asia are well endowed with navigable rivers, Subsaharan Africa does not have navigable rivers over long stretches because of escarpments. This is particularly the case for the segments reaching the ocean with several rapids and waterfalls, making navigation impractical. Differences in hydrological endowments can therefore be associated with differences in economic opportunities.
Port sites are also highly influenced by the physical attributes of the site, where natural features (bays, sand bars, and fjords) protect port installations. Since it is at these installations that traffic is transshipped, the location of ports is a dominant element in the structure of maritime networks. Where barriers exist, such as narrows, rapids, or land breaks, water transport can only overcome these obstacles with substantial investments in canals or dredging. Conversely, waterways serve as barriers to land transportation, necessitating the construction of bridges, tunnels, and detours.
The main components of climate include temperature, wind, and precipitation, with their impacts on transportation modes and infrastructure ranging from negligible to severe. Freight and passenger movements can be severely curtailed by hazardous conditions such as snow, heavy rainfall, ice, or fog.
Air transportation is particularly vulnerable to weather disruptions, such as during winter, when a snowstorm can create cascading effects on air services. There is seasonality for global wind patterns. Jet streams are also a major physical component that international air carriers must take into consideration. For an aircraft, the wind speed can affect travel time and costs. Tailwind conditions can reduce scheduled flight time by up to an hour for intercontinental flights. For instance, due to strong jet stream conditions during winter, transatlantic flights between the American East Coast and Europe can gain between 30 to 45 minutes from the scheduled eastbound flight time. However, for westbound flights, unusually strong jet stream conditions will lengthen flight time. They may, on occasion, force a flight to do an unscheduled refueling stop in intermediary airports such as Gander (Newfoundland) or Bangor (Maine). Climate change is expected to increase the strength of the North Atlantic jet stream and could lengthen westbound flights between North America and Europe.
The climate is also having an impact on transportation networks by influencing construction and maintenance costs. Since a large share of the global population lives in temperate climates, they are exposed to notable temperature variations between the summer and winter months. Large temperature variations have a taxing impact on transportation infrastructures with thermal expansion and contraction cycles that may damage infrastructure made from or resting on concrete and asphalt. Infrastructures such as bridges, railways, and pipelines require expansion joints to absorb thermal expansion and contraction of their materials. For instance, land covered by permafrost offers unique constraints for the construction and maintenance of transportation infrastructures. In temperate climates, the freeze-thaw cycle can damage transport infrastructure such as road surfaces, particularly during spring, when they are more continuous. Even volcanic eruptions, by altering atmospheric conditions, can impact transport operations. For instance, in 2010, a volcanic eruption in Iceland released large amounts of ashes into the atmosphere. This forced the closing of most airports in northwestern Europe as well as the cancellation of many transatlantic flights out of concern that the ash could damage jet engines.
From a geometrical standpoint, the sphericity of the earth determines the great circle distance; the shortest distance line between two points on a sphere. This feature explains the paths followed by major intercontinental maritime and air routes.
2. Overcoming the Physical Environment
Rapid technological developments have enabled transportation to overcome the physical environment. Before the industrial revolution, most road paths were adapted to topography. Since then, efforts have been made to pave roads, bridge rivers, and cut pathways over mountain passes. Engineering techniques in terms of arches and vaults used in Byzantine and Gothic church constructions in the twelfth century permitted building bridges across wider streams or deep river valleys. Thus, road building has been at the core of technological efforts to overcome the environment since they support local and even long-distance travel.
Road building has transformed the environment from the efforts to mechanize road transport modes to the development of integrated multilane highways. Innovations in maritime transport can be found around the world. The earliest developments came in the transformation of waterways for transportation purposes through the development of canal locks coping with adverse natural gradients. Further improvements in navigation came with the cutting of artificial waterways. Some of the earliest examples can be found in the Martesana canals of Lombardy (15th century), the Dutch canals (17th century), the Canal de Briare in France (17th century), or the Grand Canal of China (mainly from the 7th to the 16th centuries).
Further improvements in navigation technology permitted to increase in the speed, range, and capacity of ocean transport. However, the increasing size of ships has prevented canals such as Panama and many ports from servicing the largest ships. Several port authorities have thus embarked on expansion programs to cope with these new technical requirements. Passages through the Arctic Ocean are being investigated to create new international connections. Artificial islands are also built to expand port installations in deep waters.
As level ground over a long distance is important for increasing the efficiency of railway routes, the transport industry has come to modify the earth’s features by building bridges and tunneling, by embanking and drainage. From the early steam engines to the first high-speed trains, increasing motive power has permitted physical obstacles to be overcome by rail.
The role of technology has been a determinant in the development of the air transport sector. From the experiments of the Montgolfier brothers to the advent of jet aircraft, the aerial crossing of rugged terrain over a considerable distance became possible. Technical innovation in the aeronautic industry has permitted planes to avoid adverse atmospheric conditions, improve speed, increase range, and raise carrying capacity. Unlike maritime shipping, polar air routes have been a reality since the 1990s, allowing to connect North America and Pacific Asia. With the rapid rise in air passenger and freight transport demand, emphasis has been given to the construction of airport terminals and runways. As airports occupy large areas, their environmental footprint is substantial. The construction of Chek Lap Kok airport in Hong Kong led to leveling mountainous land for the airport site. Kansai airport servicing Osaka has been built on an artificial island.
3. Transportation and the Spatial Structure
The concepts of site and situation are fundamental to geography and transportation. While the site refers to the geographical characteristics of a specific location, its situation concerns its relationships with other locations. For instance, a port site relates to attributes such as the suitability of its harbor. In contrast, a port situation relates to its connectivity with its foreland (other ports) and hinterland (the inland market it serves). Thus, all locations are relative to one another, but the situation is not a constant attribute as transportation developments change accessibility levels, and the relations between locations. The development of a location reflects the cumulative relationships between transport infrastructure, economic activities, and the built environment.
The following factors are particularly important in shaping the spatial structure:
- Costs. The spatial distribution of activities is related to distance factors, namely its friction. Locational decisions are taken to minimize costs, often related to transportation.
- Accessibility. All locations have a level of accessibility, but some are more accessible than others. Thus, because of transportation, some locations are perceived as more valuable than others.
- Agglomeration. There is a tendency for activities to agglomerate to take advantage of the value of specific locations. The more valuable a location, the more likely agglomeration will take place. The organization of activities is essentially hierarchical, resulting from the relationships between agglomeration and accessibility at the local, regional, and global levels.
Many contemporary transportation networks are inherited from the past, notably transport infrastructures. Even if since the industrial revolution, new technologies have revolutionized transportation in terms of speed, capacity, and efficiency, the spatial structure of many networks has not much changed. Two major factors can explain this inertia in the spatial structure of some transportation networks:
- Physical attributes. Natural conditions can be modified and adapted to suit human uses, but they are a challenging constraint to escape, notably for land transportation. Thus, it is not surprising that most networks follow the easiest (least cost) paths, which generally follow valleys and plains. Considerations that affected road construction a few hundred years ago are still in force today, although they are sometimes easier to circumscribe with civil engineering work.
- Historical considerations. New infrastructures generally reinforce historical exchange patterns, notably at the regional level. For instance, the current highway network of France has mainly followed the patterns set by the national road network built early in the 20th century. This network was established over the Royal Roads network, mainly following roads built by the Romans. At the urban level, the pattern of streets is often inherited from an older pattern, which may have been influenced by the pre-existing rural structure (lot pattern and rural roads).
While physical and historical considerations are at play, the introduction of new transport technology or the addition of new transport infrastructure may lead to a transformation of existing networks. Recent developments in transport systems such as container shipping, long-range aircraft, and the extensive application of information technology to transport management have created a new transport environment and a new spatial structure. These transport technologies and innovations have intensified global interactions and modified the relative location of places. In this highly dynamic context, two processes are taking place at the same time:
- Specialization. From a situation of diversification, linked geographical entities can specialize in producing goods for which they have an advantage, and trading for what they do not produce. As a result, efficient transportation systems are generally linked with higher levels of regional specialization. Economic globalization underlines this process as specialization occurs as long as the incurred savings in production costs are higher than the incurred additional transport costs.
- Concentration. The continuous evolution of transportation technology may not necessarily have expected effects on the spatial structure, as two forces are at play; concentration and dispersion. Linked geographical entities may see the reinforcement of one at the expense of others, notably through economies of scale. This outcome often contradicts regional development policies aiming at providing uniform accessibility levels within a region.
A common fallacy is to relate transportation solely as a force of dispersion, favoring the spatial diffusion of activities. This is not always the case. In numerous instances, transportation is a force of concentration and clustering, notably for business activities. Since transport infrastructures are generally expensive to build, they are established first to service the most important locations. For instance, even if it was a substantial dispersion factor, the automobile has also favored the clustering of several activities in a suburban setting.
4. Space / Time Relationships
One of the most fundamental relationships supported by transportation involves how much space can be overcome within a given amount of time. The faster the mode, the more significant is the distance that can be overcome within the same amount of time. Transportation, particularly improvements in transport systems, changes the relationship between time and space. When this relationship involves easier, faster, and cheaper access between places, the outcome is a space/time convergence because the amount of space that can be overcome for a similar amount of time increases significantly. It is, however, a spatially and socially uneven process since it will impact the accessibility of locations differently. For instance, infrastructure will not be laid up uniformly, and segments of the population will experience a greater improvement in mobility because of their socioeconomic status.
Despite these uneven processes, significant regional and continental gains were achieved during the 18th and 19th centuries with the establishment of national and continental railway systems as well as with the growth of maritime shipping, a process that continued into the 20th century with the development of road and air transport systems. The outcome has been significant differences in space/time relationships, mainly between developed and developing countries, reflecting differences in the efficiency of transport systems. Differences in mobility are thus a defining characteristic of development.
At the international level, globalization has been supported by improvements in transport technology. The result of more than 200 years of technological advancements has been a space/time convergence of global proportions in addition to the regional and continental processes previously mentioned. This enabled the widespread exploitation of the advantages of the global market, notably in terms of resources and labor. Significant reductions in transport and communication costs occurred concomitantly. Thus, there is a relationship between space/time convergence and the integration of a region in global trade. Five major factors are of relevance in this process:
- Speed. The most straightforward factor relates to the increasing speed of many transport modes, a condition that notably prevailed in the first half of the 20th century. More recently, speed has played a less significant role, as many modes are not going much faster. For instance, an automobile has a similar operating speed in the early 21st century than it had in the mid-20th century. At the same time, a commercial jet plane operates at a similar speed in the 2010s than in the 1970s.
- Economies of scale. Being able to transport larger amounts of freight and passengers at lower costs has considerably improved the capacity and efficiency of transport systems. For space-time convergence, this implies that there is more capacity for a given quantity of passengers or freight being carried. Instead, the traffic can be handled with fewer trips implying that at the aggregate level, it is moving faster.
- Expansion of transport infrastructures. Transport infrastructures have expanded considerably to service areas that were not previously serviced or were insufficiently serviced. A paradox of this feature is that although the expansion of transport infrastructures may have enabled distribution systems to expand, it also increased the average distance over which passengers and freight are being carried.
- Efficiency of transport terminals. Terminals, such as ports and airports, have shown a growing capacity to handle large quantities in a timely manner. Thus, even if the speed of many transport modes has not increased, more efficient transport terminals and better management of flows have helped reduce transport time.
- Information technologies (IT). Permitted several economic activities to bypass spatial constraints in a significant manner as IT enables an improvement of traffic flows and better managing transport assets.
Yet, space/time convergence does not occur ubiquitously. In time, some locations gain more accessibility than others, particularly if they experience the accumulation of transport infrastructures and have a level of economic and political command. For instance, by the early 20th century, London was the most connected location in the world, a status reflective of the primacy of the British Empire at that time. The importance of locations reflects priorities attributed to connectivity and accessibility and variations in space/time convergence.
There is also a scale effect on space/time convergence as long-distance transportation tends to be more impacted than short-distance transportation. Therefore, space/time convergence between two cities could be more significant than within a city. This creates a duality between the regional or international scale of mobility that can occur at high speed and local scale subject o much lower speeds.
After centuries of transport developments and their impacts on geography, global accessibility reflects heterogeneous geography. Space/time convergence can also be inverted under specific circumstances, which means that a process of space/time divergence takes place. For instance, congestion is increasing in many metropolitan areas, implying additional delays for activities such as commuting. Mobility taking place in congested urban areas is at the same speed as 100 years ago on horse carriages.
Despite dramatically contributing to space/time convergence, air transportation is also experiencing growing delays. Flight times are getting longer between many destinations, mainly because of takeoff, landing, and gate access delays. Airlines are simply posting longer scheduled flight times to factor in congestion. The termination of the Concorde supersonic jet service in 2003 can also be considered a space/time divergence. More stringent security measures at airports have also imposed additional delays, which tend to penalize short-distance flights. Additionally, direct transport services can be discontinued and replaced by a hub-and-spoke structure. The “last mile” can be the longest in many transport segments. For instance, an express mail package flown from Washington to Boston in about an hour (excluding delays at takeoff and landing due to airport congestion) can have an extra one-hour delay as it is carried from Logan Airport to downtown Boston, a distance of only three kilometers.
- 1.1 – What is Transport Geography?
- 2.2 – Transport and Spatial Organization
- 2.3 – Transport and Location
- Transportation and Accessibility
- Interoceanic Passages (PEMP)
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