Criticality assessment and cascading effects: impacts of COVID-19 disruptions in public transport on marginalized groups in Dortmund, Germany, São Paulo, Brazil, and Cape Town, South Africa

INTRODUCTION

In an era marked by unprecedented global crises, the intricate interplay between spatial mobility, societal structures, and the ramifications of disruptions has come to the forefront. The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, emerged as a global health crisis in late 2019, swiftly transcending national borders and affecting people from all walks of life^[1]. As a recent and stark example of such a crisis, the pandemic brought into sharp focus the vulnerabilities of marginalized groups^[2-4]. While each crisis is distinct in its origins, this study uses the pandemic as an example to shed light on the effects of restricted mobility such as a disruption of public transport. Contact restrictions and curfews shaped and changed accessibility and the way we interact with each other. In many countries, public transport systems were influenced, which has particularly affected those relying on them and unable to switch to private vehicles or online alternatives. The impact varies depending on the restrictions imposed by the government and the existing public transport network. Disrupted mobility can have crucial effects on other areas of life, as spatial mobility is essential for reaching critical infrastructures and services^[5].

Thus, this research delves into the multifaceted impacts of disruptions caused by COVID-19 response strategies on marginalized groups in Dortmund, Germany, São Paulo, Brazil, and Cape Town, South Africa. The overarching research question probes into the indirect effects of critical infrastructure and service disruptions on the livelihoods of marginalized households, analyzing the three periods before, during, and after the pandemic. This research aims to navigate this complex terrain by focusing on critical sectors essential for societal well-being, including healthcare, food and nutrition, social work, education, and childcare, employing a criticality assessment approach. Additionally, the study explores the potential of virtual mobility and online services as substitutes for in-person services during disruptions, acknowledging the evolving dynamics of a digitally connected world.

Through the analysis of cascading chains, the study anticipates the ripple effects of disruptions in each field and interconnections between them. These cascading chains were validated through expert workshops in the respective case study areas, which included various actors and experts from academia, city administration, social infrastructures, and non-governmental organizations (NGOs). By using the pandemic as a concrete example, involved experts were able to remember a specific event and did not have to make assumptions about possible effects. At the same time, the effects of restricted public transport can also be triggered by a range of events, encompassing, for example, technical issues, adverse weather conditions, labor strikes, or financial challenges. This way, the paper contributes to the existing body of knowledge by exploring the indirect effects of COVID-19-induced disruptions in critical infrastructure on marginalized groups. By employing a cascading effects model, the study provides a nuanced understanding of how interconnected systems amplify vulnerabilities, offering valuable guidance for policymakers and urban planners to enhance resilience and equity in critical infrastructure services.

Although the pandemic was a global phenomenon, governments reacted differently in terms of restrictions. In Germany, the first COVID-19 case was reported on January 27, 2020. In the following weeks, the number of infections in Germany and the rest of the world continued to rise. In March 2020, the then-chancellor Angela Merkel appealed to the population to avoid social contact and stay home as far as possible^[6]. During the first lockdown, schools and non-essential businesses had to close^[7,8]. The government imposed restrictions on social gatherings and travel, encouraged remote work, and promoted hygiene practices such as handwashing and mask-wearing^[7]. From June to mid-October 2020, the federal government decided to ease the measures. These included returning to schools, opening certain types of businesses and services, and ending strict social distancing^[9,10]. Incidence-based measures were introduced depending on the number of cases per 100.000 inhabitants in the respective municipalities^[11]. With a rising number of infections again in autumn and winter, a renewed lockdown was imposed from mid-October 2020 to March 2021^[12], and in the spring and summer of 2021, measures were eased again based on incidence and individual vaccination status^[13]. In April 2023, over three years after the first lockdown, Federal Minister of Health Karl Lauterbach announced the end of all federal measures^[14]. Overall, Germany saw fluctuating infection rates with significant stress on the healthcare system, but the mortality rate was relatively lower compared to some other European countries, partially due to early and decisive action and widespread testing and vaccination campaigns^[15,16].

As a federal state, the lockdown in Brazil was not a centralized national measure, but rather a series of coordinated actions between the different levels of government: federal, state and municipal. In the beginning of the COVID-19 pandemic, the federal government issued general guidelines, such as international travel restrictions and social isolation measures, through the Ministry of Health^[17]. However, the implementation of quarantine measures was mainly driven by state and municipal governments, which had the autonomy to establish their own policies by considering the local epidemiological situation and health system capacity. The Supreme Court ratified this autonomy in light of the federal government's refusal to adopt more restrictive measures. This resulted in a variety of approaches across the country, with some regions implementing stricter measures and others adopting more flexible strategies. In the specific case of the state of São Paulo, as of June 2020, the Plano São Paulo was implemented as an additional strategy for dealing with the pandemic developed by the state government^[18]. This plan established criteria for easing and relaxing social isolation measures, taking into account the epidemiological situation in each region of the state^[19]. As a strategic tool in the management of the COVID-19 crisis in São Paulo, it provided clear and transparent guidelines for decision-making and actions to deal with the pandemic. However, there are reservations about its effectiveness and the implications of using algorithms and data in decision-making during the COVID-19 pandemic^[20]. Brazil faced significant challenges with high infection and mortality rates, particularly in densely populated areas and among marginalized communities^[21]. The fragmented response and disparities in healthcare infrastructure exacerbated these outcomes^[22].

South Africa implemented one of the strictest lockdown measures globally during the initial phase in response to the pandemic. South Africa had five alert levels of lockdown, with level one imposing the least stringent and level five the most severe restrictions^[23]: These alert levels were declared nationally, provincially, or in a district. As the pandemic progressed, measures were gradually adjusted following the number of infections, the health system capacity in a specified area to respond to the disease burden and other factors that would influence the level of infection, hospitalization, and mortality. The government imposed a nationwide lockdown that included restrictions on movement, closure of schools and non-essential businesses, and a ban on alcohol and tobacco sales^[24]. Additionally, the government implemented widespread contact tracing efforts to identify and isolate infected individuals^[25]. Schools, offices, and non-essential businesses were closed, and mobility within the city nearly came to a halt with strict curfew hours^[26]. The national state of disaster was lifted in April 2022. South Africa's response was marked by high compliance initially, but high-density living conditions in informal settlements make it difficult for people to self-isolate^[27]. Despite efforts to manage the pandemic through strict measures and extensive contact tracing, the country experienced high levels of infection and mortality, particularly affecting marginalized populations^[28].

These measures, while aimed at protecting public health, have also led to social, economic, and socioeconomic hardships, necessitating responses that go beyond immediate crisis management to consider long-term resilience building. The pandemic has laid bare vulnerabilities and inequalities ingrained within societies, amplifying existing disparities and leaving marginalized people susceptible to the multifaceted consequences of the crisis.

Marginalization refers to the process through which certain groups are pushed to the edge of society, limiting their access to resources, opportunities, and rights available to more dominant groups^[29]. This exclusion often results from systemic inequalities and discrimination based on various social identities. The disparities extend across various dimensions of marginalization, which include aspects of race, class, age, gender, sexual identity, disability, and the intersectionality of these factors^[30,31]. Numerous studies globally and in specific countries have highlighted the stark disparities in the impact of COVID-19 on different groups^[2,32,33]. Individuals living in poverty or facing socioeconomic disadvantage faced heightened risks, racial and ethnic minority groups experienced disproportionate impacts, and those from lower socioeconomic backgrounds encountered challenges in accessing healthcare services^[3,4,34].

Beyond health impacts, economic repercussions have been far-reaching, disproportionately affecting vulnerable populations. Job losses, income instability, food insecurity, and, in extreme cases, the loss of homes have become prevalent issues, particularly for already marginalized communities^[1]. The pandemic has also deepened social divides, exacerbating isolation, mental health challenges, and limited access to education^[35,36].

Urban planners now face the task of adapting swiftly to address immediate challenges while considering the long-term impacts on urban form, mobility, and social cohesion. This research aligns with the imperative to plan urban spaces that promote public health, equitable access to essential services, and overall well-being, recognizing that the resilience of critical infrastructures is intertwined with the societal mobility patterns that underscore the lived experiences of marginalized populations. It seeks to illuminate the multifaceted challenges marginalized communities face, delving into the economic, social, and spatial dimensions of their experiences during the pandemic. Examining the specific ways in which marginalized groups have been disproportionately affected, this research aims to uncover underlying structural inequities and develop targeted strategies to mitigate adverse effects and foster more inclusive and resilient systems for societal well-being.

THE ROLE OF INDIRECT EFFECTS OF THE PANDEMIC

Existing studies have explored the direct effects of the pandemic on marginalized groups, such as increased health disparities, economic hardship, and access to essential services focusing on the immediate health impacts and economic vulnerabilities exacerbated by the pandemic^[37,38]. However, these studies predominantly concentrate on the immediate consequences without examining the broader, indirect effects. Notably, there is a gap in literature concerning the exploration of indirect effects resulting from disruptions in critical infrastructure and services, as demonstrated by Barouki et al.^[39], indicating emerging research needs. The cascade of impacts triggered by such disruptions has yet to be comprehensively examined, posing an interesting avenue for a more nuanced understanding of the challenges faced by marginalized communities during the pandemic.

The European Union defines critical infrastructure assets or systems essential for maintaining vital social functions, health, safety, security, and economic or social well-being^[40]. They play a pivotal role in amplifying risks within an entire system, whether a region, a country, or even on a global scale, despite physical damages often being localized to specific areas. While the physical damage may be restricted to a limited area, the economic and societal effects can reverberate across regions and countries, highlighting the interconnectedness of critical infrastructures.

Criticality, defined as the relative measure of the importance of an infrastructure in terms of the consequences of its disruption or loss of function, underscores the significance of safeguarding essential services for societal well-being^[41]. Cross-cutting criteria are employed to determine criticality, including the number of users relying on the essential service, the interdependencies between sectors, the potential impact on economic and societal activities, and the geographic reach of potential incidents^[40]. These criteria provide a comprehensive framework for assessing the criticality of infrastructural assets and guiding resilience efforts. Assessing systemic criticality requires a network-wide, trans-sectoral perspective^[42-44]. The systemic criticality of critical infrastructures introduces complexities not adequately addressed by traditional place-based risk concepts, as they tend to disregard functional interdependencies between sectors and do not consider cascading effects that may take place outside directly exposed areas^[45,46].

Systemic criticality, as an emerging concept in a globally interconnected world, gauges the relative importance of an infrastructure in relation to the consequences of a disruption or failure for the security of the supply of important goods and services to society. It defines infrastructure as highly important based on structural, functional, and technical considerations within an overall system^[45]. Understanding systemic criticality becomes paramount in addressing the challenges of risk assessment and management^[47].

Past approaches of a criticality assessment often revolved around describing the impacts of a singular event, such as an extreme weather event, including a flood, on the disruption of a specific critical infrastructure and the subsequent interconnected effects. This starts a domino effect characterized by a chain reaction of similar events triggered by a single occurrence, highlighting the interconnected nature of critical infrastructures^[43]. Limited to a single infrastructure sector, such as the spread of a disturbance within the power network, the domino effect underscores the vulnerability of interconnected systems to localized disruptions.

In contrast, cascading effects encompass a broader scope, extending beyond individual sectors to encompass disruptions in essential services. Even a localized disturbance in one sector can lead to far-reaching and long-term negative impacts on service delivery across multiple sectors. For example, disrupted transport links can precipitate cascading effects in sectors vital for societal functioning, including food and nutrition, education, healthcare, and social services^[48]. These cascading effects underscore the systemic vulnerabilities inherent in critical infrastructure networks and emphasize the importance of resilience planning to mitigate their impact.

Moreover, studies often look at the interconnectivities between the respective critical infrastructures^[46,49] but do not adequately address the nuanced interplay between the effects and the vulnerabilities of marginalized groups. The COVID-19 pandemic also did not solely affect a singular place-based facility such as a health care facility or school, but rather influenced every aspect of life. Its effects transcended the traditional boundaries of critical infrastructure disruptions, presenting a unique challenge in understanding and assessing the systemic repercussions of a non-physical, global event, necessitating a systemic risk perspective.

Therefore, it is essential to investigate the specific effects of diverse COVID-19 response strategies from a systemic criticality perspective. This approach enables the estimation of case-specific indirect effects on livelihood and accessibility, considering the complex interdependencies among critical infrastructures.

CONCEPTUAL FRAMEWORK

The study employs a cascading effects model to investigate the multifaceted impacts of disruptions in critical infrastructures caused by COVID-19 response strategies on marginalized households. This model posits that disruptions in one sector can trigger adverse consequences across interconnected systems, amplifying vulnerabilities, reducing livelihoods, and exacerbating social inequalities. The starting point of these disruptions lies in restricted mobility resulting from COVID-19 response measures. Whether due to decreased availability of public transport, lockdown strategies mandating people to stay at home, or voluntary decisions to avoid public spaces for fear of infection, the restriction of mobility initiated a chain reaction of disruptions in critical infrastructure sectors. By examining the cascading effects of disruptions in healthcare, food and nutrition, social work, education, and childcare sectors, the study seeks to elucidate the intricate interdependencies within critical infrastructure networks and their implications for marginalized communities. While disruptions in critical infrastructure sectors touch all individuals, marginalized groups are disproportionately affected due to the lack of alternatives and safety nets available to them^[50,51]. The sectors are chosen due to their fundamental role in the daily lives and well-being of marginalized households and, unlike critical infrastructures such as electricity or water, they require physical accessibility by users. Marginalized communities often rely heavily on public services and have limited access to private resources, making them more vulnerable to disruptions. For example, while a transportation disruption might be an inconvenience for more affluent individuals who can afford alternative means of travel, it can severely hinder marginalized individuals' access to these essential services^[52]. This exacerbates existing inequalities and underscores the necessity of focusing on these sectors to understand and mitigate the broader societal impacts on these vulnerable populations.

METHODS

This study employs a qualitative research design to provide a nuanced exploration of the indirect effects of disruptions to infrastructure and services during the COVID-19 outbreak, particularly focusing on marginalized groups. Studies showed how disruptions of infrastructure and services resulting from the COVID-19 outbreak had an impact on marginalized groups in the form of limited access to employment, increased financial burdens, social isolation, reduced opportunities, and disrupted access to essential services^[1,35,36]. Qualitative research is chosen for its capacity to capture the complex and interrelated experiences within the selected critical sectors. Five sectors were selected where service disruption would directly impact marginalized groups: the health sector, nutrition, social work, education, and childcare.

Data collection

Literature research and expert interviews: Initial insights into cascading effects were drawn from an extensive literature review encompassing studies that elucidate the repercussions of disruptions on marginalized groups. To enrich the understanding, qualitative interviews were conducted with key experts who provided valuable insights. Initially, public transport operators were interviewed to determine the extent to which public transport collapsed during the pandemic and which groups of people were particularly affected. The unequal impact of the pandemic was also discussed with public health department employees. Furthermore, social workers from various sectors were consulted to gain insights into the lives of various marginalized people during the pandemic: Homeless individuals, people with disabilities, poor people, those with a migration background, and older adults.

Cascading effects development: The development of the cascading effects framework involved an iterative process that integrated insights from both literature review findings and expert interviews. Initially, the framework was conceptualized based on a synthesis of relevant literature pertaining to critical infrastructure disruptions and their impacts on marginalized communities. Subsequently, insights and perspectives gathered from expert interviews were incorporated into the framework, allowing for a comprehensive understanding of the interconnected challenges faced by marginalized communities. This approach ensured that the cascading effects framework accurately reflected the complex dynamics and interdependencies within critical infrastructure systems. The structure of the cascading effect chains can be seen in Figure 1. The chains start with the possible dependencies of a critical infrastructure sector on public transport and follow the impacts a disruption potentially has on employees and on the users of the respective infrastructure. Furthermore, possible interdependencies with other sectors are indicated.

Figure 1. Exemplary structure of the cascade effect chains.

Validation workshops: To fortify the validity and reliability of the developed cascading effects, validation workshops were conducted in each of the three case study areas: Dortmund, Germany, São Paulo, Brazil, and Cape Town, South Africa (see Figure 2). The workshop participants constituted experts from diverse sectors, ensuring a multidimensional perspective. For each workshop, around fifty experts, selected based on their recognized expertise and experience in their respective fields, were invited with at least ten invitations per sector to ensure enough participants from different fields. The workshops then constituted of around ten experts with two people per sector. The composition of participants was approximately 40% from practice and administration, 40% from academia, and 20% from local NGOs. This distribution provided a balanced and comprehensive view of systemic dependencies and the deliberate formation of interdisciplinary groups encouraged rich discussions, emphasizing the interconnected nature of disruptions across sectors^[56].

Figure 2. Case study areas (based on Esri, HERE, Garmin, OpenStreetMap contributors, and the GIS community).

However, it is important to acknowledge the potential for self-selection bias, as participation was voluntary and those who attended were likely those with a keen interest and available time^[57,58]. Recognizing the challenges faced by some participants, particularly those from NGOs and social workers with limited resources and heavy workloads, we supplemented the workshops with individual interviews. This approach ensured that their critical insights were included despite their constrained availability.

RESULTS

The results chapter presents a comprehensive analysis of the cascading effects of disruptions in critical infrastructure sectors on marginalized communities. Focusing on Dortmund, São Paulo, and Cape Town, it examines the interplay between healthcare, food and nutrition, social work, education, and childcare systems during the COVID-19 pandemic. This chapter begins with an overview of cascading effects across critical sectors, then delves into specific narratives from each case study area, illustrating the complex challenges these communities face. The complete and detailed cascade effects are provided as Supplementary Figures 1-5.

DISCUSSION

Reflecting on the results in the context of our research question, the profound impact of disruptions in critical infrastructure sectors on the livelihoods of marginalized households is illuminated. It is demonstrated that seemingly isolated disruptions, such as those in public transportation, can trigger cascading effects with far-reaching implications across various sectors of daily life. For instance, the closure or limitation of public transport systems not only impedes individuals' ability to access essential services but also exacerbates existing inequalities by disproportionately affecting marginalized communities as these are, compared to non-marginalized groups, more reliant on these services for mobility. Additionally, reduced mobility and confined daily routines further compound the challenges faced by these communities. Social distancing becomes particularly difficult in densely populated informal settlements, where the density of people limits the effectiveness of preventive measures^[26,61]. The inability to commute also restricts residents' access to necessary services that might not be available in their residential area.

Therefore, one key implication of these disruptions is the critical importance of mobility and accessibility in sustaining livelihoods, particularly for vulnerable populations. The findings underscore the essential role of public transportation in facilitating access to healthcare, education, employment opportunities, and social services. When transportation systems are disrupted, marginalized households face increased challenges in meeting their basic needs and accessing vital resources, further exacerbating socioeconomic disparities. Tariverdi et al.^[62] proposed a new methodology for computing urban accessibility to essential public services such as healthcare and analyzing the criticality of infrastructure components in relation to the services they provide, such as transport, based on open data. This methodology enables the identification of isolated locations and populations regarding the studied public service and could be a useful tool for further urban planning in a case as presented in this study.

Moreover, the study contributes to a deeper understanding of the broader societal impacts of critical infrastructure disruptions. Studies like the one conducted by Sunio et al.^[63] showed the impact of public transport disruption on access to healthcare facilities during the pandemic but have not looked at the subsequent impacts on other sectors yet. By uncovering the interconnectedness between different sectors, it is revealed how disruptions in one sector can have ripple effects across others, creating complex and intertwined challenges for marginalized communities. For example, we showed how disruptions in transportation can affect access to education, influencing child care and access to food, which can affect the sectors of healthcare and social work, highlighting the interconnected nature of critical infrastructure systems.

Furthermore, the findings emphasize the importance of considering intersections between critical infrastructure sectors in resilience planning and risk management strategies. By identifying how disruptions in one sector can amplify risks and vulnerabilities in others, the study underscores the need for integrated approaches that address the interdependencies between infrastructure systems. For instance, efforts to enhance transportation resilience should consider the implications for healthcare delivery, education access, and social support services, ensuring a holistic and coordinated response to disruptions.

RECOMMENDATIONS

The observed cascading effects underscore the critical importance of inclusive policies and effective governance mechanisms in mitigating the indirect impacts of infrastructure disruptions on marginalized communities. Policymakers should prioritize the development of resilient infrastructure systems that can withstand and recover from shocks while ensuring equitable access to essential services. Lessons learned from the diverse case study contexts, including the interplay between critical sectors and their implications for vulnerable populations, should inform policy formulation and decision-making processes.

Policymakers must recognize the heightened vulnerabilities of marginalized groups and prioritize interventions that address these disparities. While measures aimed at the general population can provide broad benefits, targeted support for marginalized communities is crucial for promoting equity. For instance, maintaining and enhancing public transportation services during emergencies, ensuring equitable access to digital learning tools, and supporting community food programs can help mitigate the disproportionate impacts on marginalized groups. Mobile healthcare units and social workers can also bring support directly to underserved areas, reducing the dependency on disrupted public transportation.

Building on the insights gained from the case studies, urban planners must adopt a holistic approach to infrastructure development that considers the interconnectedness of critical sectors and their potential ripple effects. Investments in infrastructure resilience should prioritize underserved areas and address systemic vulnerabilities, such as food insecurity and limited access to healthcare and social services.

For this, community engagement is essential for building resilience and fostering social cohesion in the face of infrastructure disruptions. Stakeholders should leverage the strengths and resources of local communities to develop tailored interventions that address their specific needs and vulnerabilities. Empowering marginalized groups to participate in decision-making processes and co-design solutions can enhance the effectiveness and sustainability of resilience initiatives. The case study differences offer valuable insights into the diverse needs and priorities of communities, highlighting the importance of context-specific approaches to community engagement and empowerment.

In order to this, education plays a crucial role in raising awareness about the cascading effects of infrastructure disruptions and the importance of resilience planning. By providing training and educational resources to policymakers, planners, and community members, stakeholders can enhance their understanding of complex interdependencies and build capacity for proactive risk management.

CONCLUSIONS

The findings from our case studies shed light on the profound impact of COVID-19 disruptions on marginalized households across different geographic and socioeconomic contexts. Our research question aimed to explore the cascading effects of disruptions in critical infrastructures on the livelihoods of marginalized communities, with a focus on the intersections between different sectors and the broader societal implications. Through the lens of these case studies, we can discern the intricate ways disruptions in critical sectors, such as healthcare, food supply, social work, education and childcare caused by restricted mobility have exacerbated existing vulnerabilities and inequalities, further underscoring the systemic challenges marginalized populations face during the pandemic. Our findings further underscore the importance of considering cascading effects in assessing infrastructure resilience and developing strategies to mitigate the indirect impacts on marginalized groups.