Author: Dr. Jean-Paul Rodrigue

Natural and anthropogenic disruptive events have effects on transportation systems, which can impact modes, terminals, and infrastructure differently.

1. Transportation and Disruptions

There is often more to learn from failure than success, even if failure is never welcomed. While the factors behind success can, at times, be ambiguous, the reasons for failure are commonly quite clear. The reasons why an airline is having a profitable quarter are more difficult to assess than if one of its planes was to fall off the sky.

Transportation systems are designed to operate under defined conditions with criteria such as capacity, frequency, or timeliness. Yet, disruptions such as those caused by accidents or storms are rather frequent and well-mitigated. There is a level of tolerance to disruption built into transportation infrastructures and their operations. Carriers are accustomed to mitigating disruptive events, most of which are recurring, even if randomness plays a role. A flight can be delayed or canceled for weather or mechanical reasons, and passengers rebooked to use alternatives such as other connecting flights. On occasion, a disruption takes place at a much larger scale to the extent that the safety or security of a whole region or nation is compromised. Disruptions at a global scale are rare but can be far-reaching in consequences, such as economic crises, wars, and pandemics.

While what could be defined as an emergency can be handled by local resources such as local police, healthcare, and emergency response, a disaster requires a broader intervention that could go to the national and even international levels.

A disaster involves extensive damage to people and physical infrastructure that is unforeseen in nature, scale, and extent. It is an event going beyond the anticipated capabilities to respond, which implies that their risk of occurrence has not been properly assessed, and a large share of the damage is the outcome of a lack of preparedness.

Transportation is often considered a critical infrastructure since a disruption in one of its components can significantly impact the economic and social well-being of a region or a nation. An effective way to assess how critical infrastructure is would be to consider the impacts its removal would have on the flows and activities it services. From an economic standpoint, the impacts of disruptions are dependent on three factors:

1. Their nature and level of incidence.
2. The level of exposure of populations and infrastructures.
3. The level of vulnerability of populations and infrastructures.

Several drivers have an impact on the threats and risk level of disruptions on transportation systems:

• Increased mobility. The mobility of passengers (for commuting, tourism, business, and migration) and freight has risen globally, including crossing international boundaries. Air and maritime transportation are particularly illustrative since their growth implies more vehicles and cargo in circulation. Therefore, even if the risk factors remain similar, if there is more activity, there will be more disruptions. This trend has also been strengthened by trade agreements and tariff reductions promoted by organizations such as the World Trade Organization. There are more economic opportunities, but some risks, such as infectious diseases, can spread faster and more extensively.
• Infrastructure and economic interdependency. Transportation and energy infrastructures are particularly interdependent, implying that a disruption in one infrastructure may spread to other infrastructures through propagation and back-propagation mechanisms. This interdependency is also economic, as trade is based upon respective specialization. Some parts and components are provided by a limited number of suppliers, which can be prone to risks in case of disruptions. In several sectors, such as resources and energy, supply chains are relatively rigid, implying that there are limited options for substitution. Resources such as oil require a continuous supply with limited margins to accommodate major disruptions.
• Centralization and concentration of distribution. The principle of economies of scale often leads to a centralization of network structures and a concentration of economic activities. Most transportation systems are organized as hub-and-spoke networks, particularly for air transportation, but this characteristic is also prevalent in maritime shipping. A small number of airports and ports handle a large share of the traffic. Global trade is articulated by major gateways where a few control a large share of the commercial flows. At the more basic geographical level, strategic passages impose bottlenecks for global maritime freight circulation.
• Urbanization. The emergence of large cities has led to acute concentrations of populations, a pattern significantly different than the more dispersed settlements that prevailed in rural societies. The concentration of the population equates with a concentration of risk. Thus, any disruption affecting an urban area is compounding its impacts on par with the population and infrastructure density. It is also worth underlining that many of the world’s largest cities are located in coastal areas, exposing them to an additional array of risks linked with hurricanes and storm surges.

The transport industry has responded to these drivers with massive investments in infrastructure and facilities that have expanded the capacity and efficiency of transportation systems, both at the domestic and international levels. In turn, added flows and capacities increased demands on managing physical distribution systems, including transportation, transshipment, warehousing, insurance, and retailing. These sectors are strategically important to national economies as they directly or indirectly manage risks by regulating the availability and distribution of goods. Due to their scale and connectivity, the following transportation networks are particularly vulnerable:

• Air transportation. Such networks have a nodal hierarchy vulnerable to disruptions at major hubs, while disruptions at smaller hubs will have more limited consequences.
• Maritime shipping. These circuitous nodal hierarchy networks have different considerations depending on whether the node is a hub or a gateway. Disruptions at a hub will mostly impact maritime shipping networks, while disruptions at a gateway will mostly impact the hinterland.
• Logistical networks. These sequential networks are vulnerable to disruptions impacting one element of the supply chain and the connected activities that are upstream and downstream.
• Road networks. Because of their mesh structure, road networks are not highly vulnerable to disruptions, unless this disruption is at a wide scale.
• Rail networks. While linear rail networks are vulnerable to disruptions, complex rail and transit networks have a mesh-like structure, making them more resilient.
• Power grids. These sequential networks are usually highly redundant but are subject to a hierarchical vulnerability where the higher up in the hierarchy, the more extensive the disruption.

2. Transportation Resilience

With the increasing reliance on distribution systems, any failure in transportation, due to intentional or non-intentional causes, can have very disruptive consequences and can even compromise national security over four major issues:

• Transportation supply. Ensuring that transportation modes, routes, terminals, and information systems can satisfy national security needs such as normal commercial operations, troop deployment, and emergency relief.
• Transportation readiness. Maintaining the readiness of transportation to face time-sensitive national security needs.
• Transportation vulnerability. Reducing the vulnerability of transportation modes, terminals, and users to intentional harm, accidents, or disruption from natural events.
• Illegal use of transportation. Reducing the trade of restricted or illegal goods (e.g. drugs, endangered species), and illegal immigration.

Disruptions take place over complex transportation systems and are consequently difficult to evaluate. Particularly, the non-linearity character of complex systems implies that disruption can have multiplying and feedback effects, many unforeseen and unintended. Disruptions of high severity, such as a crisis or a disaster, are likely to trigger a phase transition where the resulting transport conditions are very different from the initial situation due to adaptation and mitigation.

One of the core aspects of mitigating transportation disruptions concerns the resilience of transport systems, which is having infrastructures and modes able to withstand and recover from natural and anthropogenic hazards.

The resilience of a transport system is its capability to resume operations at a level similar to that before a disruption occurred. The less disruption in terms of capacity and fluidity and the faster a system resumes its operations to a normal level, the higher its resilience.

The frequency and the reported type of disruptions vary as some can be consistent such as weather disruptions. In contrast, others can be sporadic, such as pandemics, while others, such as cyberattacks, are steadily on the rise. Resilience is highly influenced by the network structure, particularly its flexibility, and redundancy with its capacity to remain connected as some of its parts are disrupted:

• Flexibility. Concerns the capacity to find alternatives such as new routes, new terminals, or new suppliers.
• Redundancy. Involves a level of duplication of assets, let them be paths to connect locations or additional inventory within supply chains.

Resilience is also related to the nature of the disruptions since each disruption has inherent effects. A simple taxonomy reveals that they are either natural or anthropogenic in origin.

3. Natural Disruptions

a. Extreme weather events

Many weather events, such as storms and blizzards, occur regularly and have minimal impacts on transport systems with delays, partial closures, or diversions. Others, such as floods, cyclones (hurricanes), tornadoes, and droughts, can be of disastrous proportions. Tropical cyclones are particularly harmful since they cover wide areas (a mid-sized cyclone can cover an area of 500 km in diameter), move slowly (25 km/hr), and are associated with high winds and rainfalls. There is a distinct seasonality to hurricanes, with the highest frequency in the Northern Hemisphere between August and November, with peak activity during September. In the southern Pacific and Indian oceans (no hurricanes in the South Atlantic), the period between November and April shows the highest frequency of occurrences. During a hurricane, regional air transport, and public transit systems are usually shut down, and land transportation can be severely impaired, impacting supply chains. For instance, major floods in Thailand in 2011 were highly disruptive for the electronics sector, particularly hard drives, since they accounted for 25% of global production. Hurricane Sandy, which struck the New York / New Jersey coasts in 2012, incited the preemptive shutdown of all the airports, ports, and public transit systems of the region. Due to flooding and power outages, it took several days for the system to be returned to normal operating conditions, substantially impacting commuting. Concerns are that climate change may be linked with more recurrent extreme weather events. Beyond this debate, the fact remains that extreme weather events will continue to occur, but their frequency and scale are uncertain.

b. Geophysical

Tectonic activity is the source of the most serious geophysical disasters. Earthquakes are salient forms of geophysical threats since they are difficult to predict but focus on areas in the vicinity of boundaries of tectonic plates. Tsunamis are also considered an emerging risk as a growing number of people live in coastal areas. The 2011 Tohoku earthquake in Japan is among the five largest in recorded history. While the damage by the earthquake was significant, it is the associated tsunamis that caused the most extensive damage to the Japanese transport infrastructure. Further, the earthquake significantly impacted global supply chains as Japanese automobile production fell by 50% in the following months, mostly because of disruptions in electronics, semiconductors, and automotive parts suppliers. Although areas of high earthquake occurrence are readily identified, the specific location and scale of an event remain a probability that is often difficult to conceptualize in transport infrastructure planning.

While volcanoes have always been localized and easily identifiable risks, the ash clouds they release have been a concern for air travel. For instance, the ash cloud released by the 2010 eruption of the Eyjafjallajökull volcano in Iceland forced the shutdown of most of the European and transatlantic air transport system for nearly a week, stranding millions of passengers. Since air transportation is an extremely recent phenomenon in geological times, the probability and extent of ash cloud events remain uncertain. For instance, an event of the scale of the Krakatau 1883 eruption taking place today would have profound ramifications for the global maritime and air transport systems.

c. Geomagnetic storms

They concern disturbances in the earth’s magnetic structure, mostly the outcome of solar activity, where the frequency of geomagnetic storms varies accordingly. Geomagnetic storms can impair power grids and have a higher probability of occurring around the north and south poles. Still, they are less known and often an underestimated risk. The largest geomagnetic storm in history occurred in 1859 (called a Carrington Event in the name of the British astronomer who documented the flare). Still, at that time, electrical systems were rudimentary, and their impacts on human activities were marginal. Such an event taking place today would have heavy consequences (e.g., hundreds of millions losing electric power) and would qualify as a disaster. Further, it is unknown to what extent geomagnetic storms can disrupt electric vehicles, and even if unaffected, the lack of a power grid would mean their immobilization.

d. Climate change

Historically, sea levels outside standard tides, have rarely been considered for human settlements, implying that many cities and infrastructure are built right above the upper tidal limit. Potential rising sea levels attributed to anthropogenic causes (climate change) have been a recurring concern. There are various scenarios about potential sea level rises, but evidence underlines a rise by one meter by 2100 (compared to a 2000 baseline) as almost a certainty. Irrespective of the timing, sea-level rise places critical transport infrastructure, such as ports and airports, at risk of operational damage and discontinuity. For instance, a port terminal or an airport could not be directly impaired by sea-level rise, but its access roads could compromise its commercial viability. Sea level rise would also amplify the impacts of extreme weather events, namely storm surges.

4. Anthropogenic Disruptions

a. Accident and infrastructure failure

The outcome of technical failures or human errors and where modes, infrastructure, or terminals can be damaged or even destroyed, which includes injuries, the loss of life, and property damage. Small-scale accidents frequently occur, particularly over road transportation systems, creating minor disruptions. Transportation-related accidents are mostly punctual events unrelated to a massive loss of life and damage. There are notable exceptions. An aircraft crash with a complete loss of life can be considered a disaster. Even if planes are larger and more people are flying, improved airline safety has made these events increasingly uncommon, particularly regarding accidents per passenger-km flown. Industrial accidents related to releasing hazardous cargo (particularly fuel and chemicals) in an urban area during transport or at a transport terminal are also an issue of concern.

Transportation infrastructure can fail due to a lack of (or deferred) maintenance, improper management, design flaws, or handling more traffic than designed. Bridges and similar structures are particularly vulnerable, especially from a system-wide perspective, where aging (or poorly maintained) infrastructure can impact many components within a similar timeframe. While infrastructure failure tends to be more frequent in developing economies due to a lack of investments and improper maintenance, the aging of infrastructure in advanced economies creates a new challenge.

b. Conflicts, terrorism and piracy

Conflicts such as wars and civil unrest often damage infrastructure, with transportation commonly a voluntary or involuntary target. Due to the importance of global trade and the structure of maritime shipping networks, bottlenecks (strategic passages) are subject to the risk of partial or complete closure. Terrorism has been a disruptive issue that has come to the forefront over the last two decades. For instance, the disruptions caused by the events of September 11, 2001, can be considered a disaster because of their scale and scope. More than 2,700 people were killed on the planes and on the ground, resulting in the closing of the North American air transport system for two days.

The surge in global trade in the second half of the 20th century created an environment where piracy became an issue. Shipping lines are forced to pass through constrained areas, chokepoints, namely straits such as Malacca and Bab el Mandab, along the heavily used Asia-Europe maritime routes, making the interception of ships more feasible within a delimited area. The outcome of piracy on global supply chains has been small but not negligible as ships have changed their routing, and insurance surcharges are being levied for cargo transiting through areas prone to piracy. In 2022, the War in Ukraine substantially impacted the global trade of energy and food as transport infrastructure such as ports were targeted, and trade lanes in the Black Sea were restricted.

c. Economic and political shocks

Financial and economic instability will likely play a growing role in the future as most developed nations have accumulated a staggering amount of debt, raising default and inflation risks. These events would be associated with a lack of capital for infrastructure construction, maintenance, and oversight, rendering the transport system more prone to risks, such as accidents and infrastructure failure. Due to inflation, planning large transportation infrastructure projects becomes the subject of cost overruns, undermining long-term investments.

d. Cybersecurity

The diffusion of IT for communication, managerial and operational considerations has pervaded the transport industry. However, the growing digitalization and reliance on information systems have opened opportunities for cyber-related disruptions. The causes of cybersecurity breaches can be intentional or unintentional, such as employee error (e.g. losing a laptop or a storage device retrieved by others). The consequences of such developments are multidimensional and range from data theft to operational disruptions impacting carriers and cargo owners. For instance, in 2021, a cyberattack was able to temporarily shut down the Colonial Pipeline, crossing several southeastern US states. This led to disruptions in the delivery of gasoline, diesel, and jet fuel along a critical segment of the Interstate highway system. Cyberattacks are undertaken by a variety of agents guided by their motivations and objectives. The core motivation remains financial gains and is increasingly undertaken by specialized criminal groups. The use of ransomware is on the rise.

e. Sanitary threats

A pandemic is an event with potentially profound ramifications at the intersection of natural (biological) and anthropogenic causes (people are vectors, and anthropogenic causes could mutate viruses). Yet, the risk of the event itself is challenging to assess. Although a pandemic would not directly damage transportation systems, transportation is intractably linked with such a disruption as it will act as a vector for its diffusion (particularly air transportation), and shutting down transportation services in the wake of a pandemic would compromise supply chains (food, energy, medical supplies). The COVID-19 pandemic of 2020-2022 underlined how disruptive this biological and epidemiological event was on transportation systems (see Transportation and Pandemics).

5. Planning for Transport Disruptions

As freight transportation is increasingly globalized and complex, supply chain risks are salient. Developing economies are particularly vulnerable to disruptions because infrastructure, including transportation, tends to be of lower quality and more poorly managed, and thus less resilient to disruptions. In addition to the risk, a fundamental element is who bears the responsibility for disruptions and their costs. Reconstruction and replacement costs of transportation modes and infrastructure can be substantial. International commercial transactions underline that the actor assuming the liability depends on the terms of the contract, and the same event may imply a different liability allocation depending if the cargo was damaged or lost during transportation, at a terminal, or in a distribution center.

Although a potential disruption can never be effectively planned, and even anticipated in some instances, a series of steps, known as Risk Management, can be proactively considered to prepare for an event. It adopts a dynamic and value-driven approach to building resilience, beyond identifying, assessing, and evaluating threats or opportunities. It also enhances organizational resilience by learning from successes and failures. It is based on the five following principles:

• Risk assessment. The likelihood of an event and its potential impacts should be comprehensively assessed, such as its probability (low to high) over a defined time frame and a specific area (e.g. a city or region). This should provide a prioritization of risks.
• Preparedness. In light of the potential risks, a level of preparedness should be considered in terms of potential responses. This can involve the warehousing and positioning of relief material, such as fuel, parts, and equipment, and the training of the labor force in emergencies.
• Mitigation. Concerns the immediate reaction to the event and can involve the shutting down of transport systems (particularly public transit), the evacuation of populations, and the mobilization of first response resources, namely distributing emergency relief (food, medical supplies). The goal is to control and attenuate the disruptions caused by the event.
• Response. Once the disruption has been mitigated, steps are implemented to restore capacity with existing infrastructure. This is the context in which a series of viable options can be considered. If a mode has been impaired, alternative modes and infrastructure must be considered. The goal is to maintain the operation of as many elements of the transport system as possible.
• Recovery. Concerns all the steps necessary to recover the lost transport capacity during the disruption. It can involve repairs, restarting discontinued services, and investments in new and improved infrastructures, modes, and terminals. The goal is to bring back the capacity and level of service to pre-event conditions. With the lessons learned from the disruption, more resilient infrastructure and networks are likely outcomes.

The reconstruction time of transportation infrastructure tends to be slower than that of other infrastructure. Evidence from the 1995 Kobe earthquake underlines that electric power and telecommunications were restored in a matter of weeks. Road and rail infrastructure can take several months, while it can be a matter of years for port infrastructure. Transport infrastructure, particularly terminals, is much more capital-intensive than utilities and requires specialized and heavy equipment for repair or construction. Highway and rail services can run at a lower capacity and on alternative routes. If a port is shut down, other ports can generally be used, which applies to air travel. While this is less efficient as it involves longer routes for imports or exports, it remains, in most cases, economically feasible.

Managing the resilience of transportation systems opens the door for public-private partnerships setting respective roles and capabilities. The private sector has a vast array of resources, including transportation and warehousing assets, that can be brought in during a disruption. For instance, when a large-scale weather event is predicted, such as a snowstorm or even a hurricane, it is common for large retailers to reposition the inventory of critical goods, such as water and power generators, to distribution centers and stores nearby the impacted area. Then, this inventory can be rapidly deployed.

However, recovery is contingent upon the availability of capital, equipment, and managerial expertise. Therefore, recovery is usually much faster in advanced economies than in developing economies. As there are geographical differences in the risk and exposure to disruptions, there are also geographical differences in mitigating and recovering from disruptions. Because of differences in infrastructure quality, more stringent building standards, and effective governance, a similar disruption in a developing economy is likely to have more impact than in a developed economy. These differences may even be reflected at the urban level. Depending on their spatial structure, cities may be impacted differently by a similar disruption because of the quality of their infrastructure and their built-in resilience. Irrespective of the disruption, transportation systems can be a vector for the disruption and an important component in the resilience-building process.

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Related Topics

• 9.3 – Transport Safety and Security
• B.18 – Climate Change and the Adaptation of Transport Infrastructure
• 9.1 – The Nature of Transport Policy
• 9.2 – Transport Planning and Governance
• B.19 – Transportation and Pandemics

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