Transport is vital to well-functioning economies. The physical infrastructure is needed to accommodate this. The most common types of transport infrastructure are roads, railroads and ports (dry ports, seaports/ waterways and airports). These are the hard physical infrastructure components of wider transport systems that include soft infrastructure like policies and regulations, and the institutions responsible for planning, financing, operating and maintaining these systems. All these components are interconnected into transport systems. As societies change, economies grow and new markets emerge, these systems, at least in theory, need to be regularly upgraded in order to remain “fit for purpose”. However, when sudden events take place – a major technical failure, serious accident, floods or earthquake – unless these systems have in-built resilience, they can be seriously disrupted. The growing degree of the interdependencies of the hard and soft infrastructure components can increase the vulnerability of such systems, making these disruptions more serious, longer lasting and potentially debilitating with serious impacts across economic sectors.
In the past, transport infrastructure systems were less complex. Causes of disruptions were easy to detect and repair (e.g. railroad switches were operated manually and a local blacksmith could do repairs as opposed to current operation from a distance through communication lines and power supply through grid connectivity). Nowadays, infrastructure supports increasingly complex global supply chains and any disruption can spread along these chains depleting value of today’s highly interdependent economies. The ripple effects can be significant and severe. Transport systems have become more vulnerable to disasters by the mere fact that they spread across a wider geographical area and more sectors.
A real-life example illustrates such connectedness: when severe snow conditions hits the US Midwest, road traffic can be interrupted for a period of time. Obligatory crew changes for inland shipping (navigation itself is not problematic in snow conditions) cannot take place due to obstructed road traffic. Barge traffic gets disturbed and due to the tightly fit longrange planning schemes, the effects are felt all the way to the seaports at the Gulf Coast.
Other examples of dependencies can be found in reliance on telecommunication or power supply, or availability of specialized craftsmen for emergency repairs after disruption. By systematically assessing vulnerabilities due to these dependencies, and ensuring the transport system has the ability to absorb shocks and bounce back rapidly, transport system resilience can be enhanced.
Creating a framework to improve resilience of transport infrastructure systems.
This insight article aims to provide guidance on how to improve resilience of transport systems in light of the multitude of dependencies along these systems. A literature review reveals that no common framework for resilience of transport systems is readily available. While debates about how to capture resilience are ongoing, resilience of infrastructure systems is gaining interest in the academic community (Boin, A., & McConnell, 2007; D’Antonio, S. et al, 2009; Kong, D. et al 2012; McDaniels, T. et al, 2008; Petrenj et al 2011; Rogers, et al 2012; Vespignani, 2010). Considering infrastructure as a technical system, a widely cited approach from O’Rourke (Rourke, 2007) elaborates on the work of Bruneau (2003). This framework comes from the domain of resilience of communities exposed to earthquake events. On the basis of this framework, more detailed parameters have been identified through literature and document study in order to adapt this to a tailor made framework for transport systems. On the basis of mentioned literature and document study, the original framework of Bruneau has been adapted for transportation systems in general and broken down in a series of parameters relevant for transport systems, as follows:
By carefully assessing the system on the basis of characteristics as shown in the framework, resilience can be improved by balancing and preparing on the four major dimensions:
- Robustness: by improving robustness the transport system will be able to resist shocks and prevent disruptions.
- Redundancy: when redundancy is available a disturbance will be compensated for and the effects on the transport system should be contained.
- Resourcefulness: in case a disturbance does take place, relevant organisations must be prepared and ready to respond and deploy necessary resources to take action.
- Rapidity: having considered different potential scenarios the system can quickly respond and recover. Easy to replace parts/modules/assets, predefined deviation routes are all good examples.
The characteristics of the four major dimensions of resilience of transportation systems are described in more detail and can be used as a checklist to reduce the impact of disasters occurring in the transportation system.
Robustness is the capacity to withstand shocks without losing functionality. The status of assets plays a role in this. Through wear and tear or maintenance shortcomings (e.g. rust, cracks in concrete) the assets will gradually lose some of the initial capability to withstand shocks. Capacity to withstand climatologic variations is captured in the original design of assets, but exposure could have changed over time (e.g. excessive rainfall flooding roads, extreme heat jamming a bridge blocking it from opening; and these events becoming more and more frequent). The physical interdependence means the robustness is dependent on other components of these systems (e.g. water pumps keep tunnels dry but are dependent on electricity, sensors and data communication). Geographical interdependency relates to robustness to shocks along the whole system with down and upstream linkages (e.g. for a waterway a failure of a lock disrupts traffic in an entire river – up and down stream). Logistical interdependency relates to robustness in term of dependencies, which are not physical or geographical (e.g. the ability of personnel that operates assets and networks to go to during extreme weather events).
Redundancy with regards to local workarounds leads to the question whether infrastructure networks have alternative routes available: e.g. goods being able to be taken to destination by roads or railways. For waterways this can be particularly problematic, as river systems have a natural pattern without options for diversion. Man-made canals can offer alternatives, but might not be able to accommodate similar ship/convoy sizes. Air traffic is the easiest, relative speaking, as planes can be diverted to alternative airports when needed. Doing so does however rely on the availability of local alternative transport modes to reach the final destinations. By having local workarounds (e.g. traffic over shoulder, double lock chambers for navigation) readily available, the system can keep up functionality and therefore be considered resilient. Hence, traffic can be diverted to alternative routes, the effects of failing functionality somewhere in the system can be reduced. Such redundancy can be applied either locally, or on a much wider scale (e.g. alternative routes through the Alps in Europe provide alternatives for long distance north south trips; in Sub-Saharan Africa goods can be rerouted through different transport corridors). In some cases it might even be worthwhile considering what alternative modes of transport can be used in case a natural disaster disrupts an entire mode of transport. Parallel waterway and railroads (e.g. the Rhine river in Europe or the Columbia river in the US) do have such capabilities to offset disruptions. But such redundancies are not always straightforward; the use of alternative modes does require consideration of terminals to shift cargo, transport capacity on alternative systems, and pricing schemes that do not obstruct further trading of cargo.
In the event that natural disasters do disrupt transport, a resilient transport system has the ability to restore functionality, e.g. repairs, to bounce back. Funding, contingency or emergency, is needed to pay for the costs and should be readily available to keep downtime low. Expertise and manpower are needed as well. But when natural disasters disrupt the systems it can be hard to get the right personnel in the right place at the right time especially when competing demand of the personnel is high. Being prepared for this is crucial to resilience. As with manpower, availability of equipment and materials can be similar challenges. In addition, lack of availability of specialized parts or failing ancient elements in assets cannot be easily overcome as fabrication of those parts often has long lead times.
When infrastructure is resilient, that is, designed and operated in a way that can quickly be restored after lost functionality, disruption effects will be limited. By using systems, assets and parts that are easy to replace, teams are trained and skilled in emergency response and scenarios are thought-through, restoration time can be significantly reduced. Smart sequencing of such efforts can considerably reduce downtime of a variety functionalities so bouncing back after a shock starts rapidly and does not have to await the last repair to be made.
The way forward
Transport infrastructure systems have been little studied with respect to barriers to address resilience on a systems scale. Nonetheless, changing conditions due to climate change provide an extra challenge to keep operation service at required levels. In this insight article a general framework is shown to analyse the resilience of transportation systems by making use of specific resilience frameworks as used in available literature.
Infrastructure providers and affiliated organizations are facing an ever-growing challenge of managing infrastructure. Disasters regularly affect transport systems and when they do, the nature and context will often differ from disaster to disaster. This makes it harder to be adequately prepared to deal with all the complexities of the system in relation to a disaster. By using the frameworkshown, the organizations responsible for the smooth running of these transport systems can find generic guidance in:
- Reducing the impact of the disaster
- Reducing the duration of the disruption
- Balancing spending of resources to improve resilience
While these elements can be useful in operations, they are fundamental in the development of new infrastructure, or when expanding current systems.
- Boin, A., & McConnell, A. (2007). Preparing for critical infrastructure breakdowns: the limits of crisis management and the need for resilience. Journal of Contingencies and Crisis Management, 15(1), 50-59.
- Bruneau, M., Chang, S. E., Eguchi, R. T., Lee, G. C., O’Rourke, T. D., Reinhorn, A. M., … von Winterfeldt, D. (2003). A Framework to Quantitatively Assess and Enhance the Seismic Resilience of Communities. Earthquake Spectra, 19(4), 733–752.
- Kong, D., Setunge, S., Molyneaux, T. C., Zhang, G. M., & Law, D. W. (2012). Australian Seaport Infrastructure Resilience to Climate Change. Applied Mechanics and Materials, 238, 350-357.
- McDaniels, T., Chang, S., Cole, D., Mikawoz, J., & Longstaff, H. (2008). Fostering resilience to extreme events within infrastructure systems: Characterizing decision contexts for mitigation and adaptation. Global Environmental Change, 18(2), 310-318.
- Petrenj, B., Lettieri, E., & Trucco, P. (2011). Towards enhanced collaboration and information sharing for Critical Infrastructure resilience: Current barriers and emerging capabilities. In The 4th Annual International Conference on Next Generation Infrastructures, Virginia Beach, Virginia.
- Rogers, C. D. F., Bouch, C. J., Williams, S., & et al. (2012). Resistance and resilience of critical local infrastructure. In Proceedings of the Institution of Civil Engineers (p. 11).
- Rourke, T. D. O. (2007). Critical Infrastructure , Interdependencies , and Resilience. The Bridge, National Academy of Engineering.
- Vespignani, A. (2010). The fragility of interdependency. Nature, 464(April).