# Resilience Analysis of Traffic Network under Emergencies: A Case Study of Bus Transit Network
## 2 Related Literature
### Resilience Research in Transportation
Resourcefulness and rapidity determine the ability to restore functionality during the recovery phase. In transportation network systems, resourcefulness generally refers to the repair capabilities of available maintenance units after a disaster, while rapidity refers to the ability to utilize these resources fully and quickly restore service levels to pre-disruption levels [5]. Almost all definitions of resilience in transportation networks define the resilience of transportation systems from two perspectives: one is the ability to maintain functionality under disruption, and the other is the time and resources required to restore performance levels after a disruption. As shown in Figure 4, based on the resilience cycle of transportation network systems, the first observation angle is related to the disruption phase, from the occurrence of the disruption at \(t_{0}\) to the time point \(t_{1}\) when the system performance reaches the minimum value. The second observation angle is related to the recovery phase, from the start of recovery at \(t_{1}\) to the time point \(t_{2}\) when the system performance recovers to a stable state. The resilience cycle of transportation network systems is different from that of other fields. In other fields, the resilience cycle may not have a disruption phase, and the system performance will immediately decrease to the minimum value at \(t_{0}\) when a sudden event occurs, such as in the scenario of earthquakes affecting communities. In transportation network systems, the disruption phase often lasts for a period of time, such as in scenarios where hurricanes or heavy rain cause damage to the system. Regarding the resilience cycle of transportation networks, [PERSON] also proposed a variant of the resilience cycle for transportation networks under the impact of hurricanes, where \(P(t_{0})\) and \(P(t_{2})\) may not be equal, meaning that the system does not need to recover to its original performance level before the disruption [36]. Figure 4: Resilience cycles based on disruption and recovery. Therefore, based on the existing definitions of the resilience of transportation network systems in the literature, this paper proposes the following definition of resilience for urban transportation network systems: the ability of the system to resist, reduce, and absorb the impacts of disturbances (such as shocks, interruptions, or disasters) while maintaining an acceptable level of service (static resilience in terms of network structure), and to restore normal and balanced operations within reasonable time and cost (dynamic resilience in terms of spatiotemporal aspects of the transportation network). Concepts and Characteristics Related to Traffic Network Resilience:  
There are many concepts and characteristics related to traffic network resilience, such as adaptability, robustness, absorptive capacity, interdependence, system efficiency, speed, and redundancy. However, depending on different research perspectives, scholars sometimes use the same term in different ways to meet different research needs. For example, [PERSON], [PERSON] et al. believe that if a system is robust and resilient, then it can resist most disturbances [37]. [PERSON] constructed an evaluation index system for urban rail transit resilience from three aspects: absorptive capacity, adaptability, and recovery ability [38]. [PERSON], [PERSON] believes that if a system is robust, prepared for emergencies, and has the ability to recover within an acceptable time, then it can more easily and quickly recover from disturbances [39]. He, [PERSON] believes that if a system is redundant relative to its subsystems, then it can absorb most disturbances and impacts [40]. [PERSON], [PERSON] believes that if a system cannot be restored to its initial operating phase, then it can adapt and transform to different balance and operating phases [41].