PLAY 7

The Future of Network Resilience

This playbook comes at a time when extensive research is underway on building network resilience at the regional, state, federal, and global levels. The summary of available frameworks given in Appendix C and the network resilience toolkit given in NCHRP Web-Only Document 391, Volume 2, provide an overview of the state of this work at the time of this Network Resilience Playbook. The overview of existing tools and methods also reveals several areas of emerging research on which further work is needed to enable resilience teams to address resilience needs at the network level.

New Approaches to Economic Impact

As documented in NCHRP Report 732, significant attempts have been made to apply traditional cost-benefit and economic methods to resilience enhancements at the project level.³⁶ As discussed in Play 6, there are intrinsic limitations to applying these methods. The following limitations to quantifying the economic value of resilience investments can be addressed by future research:

Temporal Nature of Benefits and Impacts: The economic benefits needed to justify an investment typically rely on a constant stream of benefits over the multi-year life of an investment. A resilience improvement must be justified on network-wide benefits that can occur in a brief time. Furthermore, traditional cost-benefit methods discount benefits in relation to costs based on the year of accrual. In the case of a resilience investment, the year or duration of benefits is unknown at the time of investment. Figure 51 demonstrates how NCHRP 732 recognizes this issue. However, there is no best-practice methodology for assessing trade-offs between high-impact/low-frequency events against more traditional benefit streams (and their associated impacts) when evaluating scenarios at the network level.

Likelihood of Disruptions: The economic benefit of a resilience investment is predicated on the likelihood of a disruption. While Monte Carlo methods are recommended by the EPA for assessing risk likelihood, there is not yet a best practice in comparing speculative benefits when considering transportation investment payoffs.³⁷

Unpredictability of Disruption Timing and Costs: Unlike traditional economic analysis, where the base case condition on which an investment improves can be understood as a continuation of a current deterioration trend, in the case of a resilience investment, the benefit could vary depending on the time of year when the unknown disruption occurs; how far into the future the disruption occurs; other complementary projects or countermeasures that may come into effect before the disruption occurs; and whether the disruption occurs along with other disruptions that may multiply its effects. There is no typology of economic disruption profiles for navigating these assumptions in benefit-cost or economic impact analysis.

Structural Economic Assumptions: While NCHRP 732 recognizes the duration of disruptions as a key determinant of impacts (as shown in Figure 51), the report references traditional economic impact models like IMPLAN, REMI, TREIDS, and LIFT, all of which presume changes that affect long-term, annual economic performance. Figure 51 illustrates how the economy recovers from disruption impacts in the long term. However, this does not mean that the wider impacts and their multiplier effects do not occur in the year of disruption or are without economic significance. Adaptation of social accounting matrices to account for near-term costs is needed to adequately model disruption scenarios. For example, if the population of an entire city is unable to work for a month, a model of annual input-output relationships will not capture the impacts, yet the impacts still accrue and are relevant to a network resilience investment.

Social Equity as a Network Paradigm

Throughout this playbook, recommendations are offered for incorporating noninstitutional stakeholders into planning for supply-chain resilience and wider value-chain resilience planning. Play 2 observes the role that existing FACs, MPO committees, and business groups can play in establishing foundations for a network resilience team. Furthermore, the Transportation Network Resilience Awareness Challenge (given in Appendix D) serves as a resource for initiating stakeholders who are not transportation or supply-chain professionals into the process of network resilience planning.

Low-income, minority, disabled, and other traditionally disadvantaged stakeholders are vulnerable to the supply chain and value-chain effects of network disruptions in unique ways. The supply-chain aftershocks of the COVID-19 pandemic revealed how nondriving populations or households whose financial sustainability is jeopardized by even 1 or 2 days of business closure during a disruption face impacts not widely understood by agencies and corporate entities managing disruptions. Furthermore, food and medicine deserts in the United States can be exacerbated by disruptions in ways that cause significantly greater effects for different users of the network. COVID has revealed that not only the access to goods but also the price of goods can be sensitive to disruptions in ways that have significant impacts on households with limited liquidity. Furthermore, low-income and minority populations can play more different occupational roles in freight carriage, warehousing, and distribution than the managers who make decisions about disruptions. The “In Their Own Words” case study of the Flagstaff MPO engaging its disadvantaged stakeholders to define resilience needs and impacts in their terms is instructive of the need for further research to develop and illustrate processes that shape a resilience agenda from a social equity perspective.

Decision Support Technologies

The network-robustness and cascading-effects models in NCHRP Web-Only Document 391, Volume 2, are based on a larger body of data that cannot be fully illustrated in this playbook or the demonstration cases provided in NCHRP Web-Only Document 391, Volume 1. However, the summary displays from the models in NCHRP Web-Only Document 391, Volume 2, contain significant information about the different mix of occupations, industry activities, essential services, income classes, driving versus nondriving populations, and other characteristics associated with network vulnerabilities.

Interactive decision support technologies like Tableau, Microsoft Power-BI, ESRI Arc StoryMap, Community Viz., and others can be further explored to platform cascading-effects models and scenarios to provide both special and quantitative comparisons of vulnerability profiles for different resilience clusters or scenarios. Furthermore, the travel models available at most transportation agencies (as used in the examples) are not initially developed or calibrated for resilience-planning purposes. However, enhancements available in the modeling literature offer ways for

models to include greater seasonal detail, more detailed socioeconomic data at the traffic analysis zone level, and more intricate representations of travel cost and elasticity. These model features are currently only integrated into more complex models as their utility in simulating traffic flow is under study. However, with the finding that traffic models can play a significant role in developing and evaluating resilience scenarios, further research is warranted on how to customize models to advance cascading-effects scenario capabilities.

Cybersecurity in Network Planning

The Transportation Network Resilience Awareness Challenge offers a module on cybersecurity to facilitate dialogue among network ecosystem partners in this emerging area. Cybersecurity initiatives have often been handled at the individual organization level due to the sensitive nature of cyber vulnerability and the need for organizations to control their cybersecurity approaches. However, shared cybersecurity strategies such as (1) shared access controls and protocols for monitoring and reporting breaches among public agencies, shippers, carriers, and different modal operators; (2) regular and coordinated updates and checks on cybersecurity safeguards; and (3) collaborative exercises and drills to enable network partners to anticipate and respond to cybersecurity disruptions at the network level can enhance cybersecurity in ways found important by the case research but not currently included in best practices. For this reason, further research into network-level cybersecurity solution sets is warranted.

Network Solutions Throughout the Resilience Cycle

As discussed in Play 6 (and shown in NCHRP Web-Only Document 391, Volume 2), most resilience diagnostic tools and potential solutions focus on the preparation part of the resilience cycle and the physical components of the resilience ecosystem. To some degree, this is intuitive. Agencies conduct most of their resilience planning between disruptions, during the preparation period of the resilience cycle, and physical infrastructure is the hardest resilience element to adapt or mobilize as a disruption approaches. However, softer resilience elements—such as response and recovery technologies and intangible solutions aimed at operations, knowledge management, decision support technologies, and other solutions for institutions, households, and businesses—can be valuable tools when building long-term resilience at the network level. The concept of the resilience team (as introduced in Play 2) and the resources in this playbook can serve as a starting point for defining team roles and capabilities. However, new research into network solutions and roles during the resilience response and recovery phases and new solution sets at the institutional, business, and individual levels are needed for resilience teams to reach their full potential.

Implementing the Playbook and Its Resources

Even without subsequent research as described, this playbook and its associated educational modules, methodological demonstrations, case studies, and other resources can significantly aid resilience-planning efforts. An NCHRP implementation effort (under the NCHRP Project 20-44) is recommended to apply the plays and integrate them into typical planning efforts. An ideal pilot implementation project would involve a host of three to four sites to implement resilience plays in different contexts, which may include:

1. A resilient corridor study or small area plan.
2. A state or regional resilience cluster study.
3. The scoping of a resilience team from a standing freight executive committee or MPO committee.

4. A scenario-based supply-chain resilience investment plan, comparing the effects and business case of resilience investment options within the context of a resilience plan, freight plan, or larger LRTP.

An implementation project along these lines would provide “proof of concept” for the guidance laid out in this playbook. Putting the plays into practice would also provide an opportunity to refine the methods based on real-world experience and add to their value by identifying new contexts in which to apply them.

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