# Resilience Analysis of Traffic Network under Emergencies: A Case Study of Bus Transit Network
## 2 Related Literature  
### Resilience Theory Research  
The term \"resilience\" originates from the Latin word \"resilire\", which means \"to rebound or recoil\". In 1807, the physicist [PERSON] first used the term to describe elastic deformation in the context of materials science [1]. In 1973, [PERSON] first introduced resilience as a concept in the field of sustainability science [2]. He defined resilience as \"the persistence of relationships within a system and is a measure of the ability of these systems to absorb changes in state variables, driving variables, and parameters\" [3]. In subsequent multidisciplinary research, the concept of resilience has been widely applied, including in the fields of ecology [4], economics, transportation [5], supply chain management [6], strategic management [7], and safety engineering [8], among others. The number of resilience studies from 1973 to the present is shown in Figure 1[9]. However, despite the widespread application of resilience research, the concept remains unclear in many interdisciplinary developments and studies [10]. Based on this, [PERSON] et al. argue that the concept of resilience may inherently have fuzzy attributes, as it has different definitions when serving specific goals in different disciplines. Resilience is more of a way of thinking for analyzing problems rather than a fixed concept [11]. Therefore, if there is no consensus on the ambiguity of the concept of resilience in various fields of research, a rigid definition of the concept of resilience may cause confusion. [PERSON] et al. suggest that systematic thinking is necessary for resilience research and that each resilience scenario needs to be defined, starting with clarifying the system definition, system boundaries, external environment, and interactions between the system and the external environment, and then identifying changes in system inputs and outputs [12]. The current academic research on resilience lacks systematic empirical studies [10]. Resilience research is mainly conceptual and focuses on developing a static knowledge base for related research fields by establishing basic concepts and principles [10]. The related research in various fields based on resilience has mainly gone through the following three stages:  
1. Fragility. The term \"fragility\" has many meanings, but it is usually associated with the vulnerability of a system to external influences. [PERSON] et al. conducted a systematic study of fragility in the context of climate change and proposed four hypotheses for assessing fragility in the process of adapting to climate change. Finally, they defined fragility as the degree to which a system is affected by climate change [13]. [PERSON] and colleagues defined the concept of fragility from a more macro perspective as the response of a system to a series of influences, including the degree of exposure to external stresses and sensitivity to perturbations [14]. The concept of fragility is inherently complex, involving multiple variables, and can be considered a dynamic entity [15]. In more specific studies of fragility, [PERSON] identified the conceptual linkage between fragility, resilience, and adaptability [16]. Based on this representation, [PERSON]'s study considered resilience as a subset or component of a system's response capacity, which involves the ability of a system to adjust and regulate its response to disturbances, use any available measures, and respond to the consequences of system changes [17]. It is therefore generally believed among researchers that studies on system fragility are often conducted as an aspect of resilience research [18]. 2. Adaptability. As [PERSON] et al. showed in their example of studying the resilience of social-ecological systems, system adaptability is related to the creation of novelty and self-learning  
Figure 1: Number of resilience studies during 1973–2022. mechanisms in ecological systems [19]. [PERSON] describes system adaptability as ecological resilience acting as the system's robustness to changes in resilience [20].