Author: Dr. Jean-Paul Rodrigue
Bottlenecks impose delays and restrictions in the normal flow of transportation and can be related to infrastructure, regulations or operations.
1. Transport Bottlenecks
The formation of bottlenecks is the outcome of three factors that can be individual or concomitant, for complex bottlenecks:
- Infrastructure. Represent the most fundamental factor in the creation of bottlenecks at terminals and connectors. While land transportation (road and rail) tends to be more constrained by the capacity of their connectors, air, and maritime transportation are more constrained by terminal capacity. Constructing transport infrastructure must contend with the scarcity of capital, labor, and land, which results in a compromise where capacity is more a function of available resources than potential demand. In areas where resources are limited, this scarcity increases the risk of infrastructure bottlenecks as investments do not match the required capacity. Further, delaying maintenance can potentially lead to infrastructure failure, creating a temporary bottleneck at the point of failure. Transportation relies on conveyances, which can be capital intensive and in limited supply, which is a source of bottlenecks since the number of available vehicles may not match the demand. A series of natural (e.g. storms) and anthropogenic (e.g. accidents) events can create bottlenecks by damaging or disrupting transport infrastructures.
- Operations. Services provided by carriers and logistical service providers can create bottlenecks if they are not fully available, including their level of performance, which is associated with high costs, delays, and lack of reliability. Each of these performance factors can be a bottleneck on its own along the transport chain. The lack of drivers and operators for conveyances and their level of qualification are also hindrances impacting capacity.
- Regulations. For international movements, customs clearance can be a notable bottleneck, particularly for freight that can be delayed for several days awaiting inspection and clearance. Cabotage restrictions may impose the usage of specific gateways as some destinations could only be reached by national carriers. In highly regulated environments there could be competition control, preventing actors from entering or exiting the market or providing subsidies or disincentives to specific modes and terminals. These policies have the unintended consequence of creating bottlenecks since they may hinder capacity development, or reduce capacity. If transportation modes are regulated in a manner where coordination between carriers is complex, this may create interoperability bottlenecks.
The effects of bottlenecks can be evaluated on three dimensions:
- Impact. A common and notable bottleneck effect concerns a reduction in capacity, often related to a specific node or connector. Sudden capacity reduction remains a core concern of how bottlenecks impact transport systems. Another form concerns efficiency issues, where a bottleneck causes delays and a decline in transportation reliability.
- Time horizon. Bottlenecks can be chronic, enduring, and difficult to change without substantial infrastructure investments or regulatory overhaul. Bottlenecks can have a temporary effect when linked to a single and unusual event that reduces capacity and efficiency. For instance, repairing or upgrading transportation infrastructure will create a temporary bottleneck that ceases once completed.
- Extent. A bottleneck can have a direct and indirect effect on transportation. A direct effect is usually observed at the location of the bottleneck, such as loss of capacity, while an indirect effect may concern other locations or sectors that are impacted by the bottleneck. For instance, if a bottleneck delays the delivery of parts and finished goods, this may delay the related activities.
Further, each transportation mode has a distinct network structure, which is conducive to the formation of mode-specific bottlenecks.
2. Bottlenecks Across Transport Modes
Bottlenecks have a propensity to have specific locations and a distinct geography, which is related to the concerned mode.
- Road bottlenecks. At the local level, various forms of traffic disruptions are common sources of bottlenecks, which can be chronic (such as an intersection) or temporary (an accident or a storm). Observing traffic conditions over a period of time allows to clearly identify the main bottlenecks of circulation, particularly bridges and tolls. They become particularly salient during commuting cycles that provide recurring traffic surges, commonly above capacity limits. Bottlenecks can also occur for regulatory reasons, such as delays at border crossings or weight inspections for trucks.
- Rail bottleneck. Rail transportation is notably dependent on terminal capacity, making such facilities the source of bottlenecks. For commuting, central rail stations can become major bottlenecks linking different systems of urban passenger transportation. Similar restrictions apply to rail freight transportation, an issue made more complex by the variety of cargoes (containers, grains, RORO), each often requiring a different type of terminal facility. Still, there is a strong distinction between rail container terminals and other forms of cargo carried by rail. Interconnectivity between rail transport systems can be a source of bottlenecks when users and cargoes have to switch terminals to access another part of the network. Less common gauge changes can also impair the connectivity of rail transportation.
- Maritime bottlenecks. The dependence on port terminal capacity is salient in maritime transportation, with constraints such as depth, the core feature defining capacity. Maritime transportation cargoes depend on a variety of specialized terminals that can be bottlenecks since the capacity of one terminal usually cannot be substituted for another. At the global scale, strategic passages are important bottlenecks that articulate the structure of shipping services. Locations such as Suez and Panama are important bottlenecks because of their restrictions on transit capacity.
- Air bottlenecks. The ultimate capacity of air transportation is defined by airport capacity, particularly runways. Further, airlines may consolidate their operations at specific hub airports, which play a very important role in regional air transport capacity. Some airports have a strong cargo orientation being hubs of an extensive air distribution network, particularly for parcel carriers.
3. Mitigating Inland Bottlenecks: The Emergence of Landbridges
Landbridge movements, the usage of a land segment to ensure the continuity of a maritime segment, have taken place throughout history. They tended to involve short land segments since inland transportation was more costly than maritime transportation, creating bottlenecks. The Silk Road can be considered one of the first significant landbridge and the exception to the short land segment rule. Due to the long distances involved and the difficulties of providing maritime services, land-only routes prevailed well into the 15th century. Even the existing maritime trading routes to Asia, from Antiquity and onward, required a short landbridge from the Red Sea to the Mediterranean. This endured until the Suez Canal was completed in 1869. A similar situation applied to the Panama isthmus, which was used as an overland route (as well as other Central American passages) between the Atlantic and Pacific Oceans until the Panama Canal opened in 1914. The development of rail networks permitted the change of the conventional short-land segment dynamic of landbridges to long-distance inland services.
One of the first modern landbridges was implemented in the 1880s by Canadian Pacific Railway. Its goal was to improve the shipping time of high-value Asian commodities, notably silk and tea, from the Far East to Europe (and also to the US eastern seaboard), using Canada’s transcontinental rail link. The so-called “silk trains” disappeared in the first two decades of the 20th century, and with them, significant landbridge activity. The transport benefits of both the Suez and Panama canals negated the advantages of most overland routes for at least half a century after their construction. It was not until the late 1960s that changes in trade flows, capacity issues, and geopolitics (particularly for the Suez Canal) would lead to renewed interest in overland routes. From a passenger transport perspective, landbridge routes were important across the Americas and Central Asia, but lost their importance with the development of air travel. Such services are now mainly relegated to freight. Although the term landbridge can refer to any inland long-distance connection, it can be nuanced into four major types of landbridges depending on the type of inland connectivity.
The setting of modern landbridges is strongly associated with developments in intermodal transportation, which was considerably improved by double-stacking trains but also by more efficient port and rail terminals. There are two major characteristics of an intermodal landbridge freight service:
- First, the freight forwarder issues a single bill of lading that covers the entire intermodal journey.
- Second, the goods remain in the same container for the entire journey.
The North American landbridge is the world’s most extensive in terms of capacity. In 1979, American Presidents Line (APL) ran the first dedicated express container TOFC (Trailers On Flat Cars) trains across the United States between Los Angeles and New York via Chicago. In 1985, a revolution was achieved by APL with the introduction of double-stack container rail services (COFC; Containers On Flat Cars) with capacities of up to 600 TEU (about 300 forty-foot containers) in a unit train. Shipping companies were particularly eager to see the emergence of these types of services as using the Panama Canal incurred substantial delays, which could be bypassed by the landbridge.
The Eurasian Landbridge is also emerging. In 2004, the first doublestacking rail service in China began, linking Shanghai and Beijing. In 2014, establishing long-distance rail corridors between China and Western Europe became a formal strategy known as the Belt and Road Initiative. This resulted in investments in the development of rail infrastructure in Central Asia and the establishment of intermodal services between selected Chinese and European cities.
Landbridges are also being challenged by economies of scale in maritime shipping, which can be perceived as somewhat paradoxical. The initial application of economies of scale in containerized shipping induced the setting of inter-range services that were complemented by landbridge services. In North America, this led to an acute differentiation of maritime services for the East and West coasts and the usage of the landbridge to service East Coast markets from West Coast ports. Yet, new generations of post-Panamax containerships, particularly above 8,000 TEU, and contemporary supply chain management strategies impose capacity and reliability constraints on long-distance rail that are challenging to meet. With the expansion of the Panama Canal in 2016, the North American and the Eurasian landbridges face a new commercial environment and more competitiveness between the East and West coasts.