The word “resilience” is derived from the Latin word “resilio”, meaning “return to the original state” [25], and is usually used to describe the ability of an object or system to return to its original normal state after being affected by a destructive event. The concept of resilience was first applied to physics, which refers to the resilience of a system after external disturbances. In the 1970s, the resilience theory was first applied to the field of systems ecology by Holling [26], a Canadian ecologist. Since then, the discussion of resilience in specific fields has ranged from ecosystems to economic and environmental systems to transportation systems. The resilience of the transport system is related to the shelter and emergency response ability of a city against disasters. As a guarantee for the safety and good operation of a city during disasters, transport resilience has become the focus of researchers of resilient cities. Its general definition can be described as the ability of a transport system to resist the effects of disruptive shocks and maintain its normal functioning [22,23,27,28]. Disruptive shocks here include natural disasters such as earthquakes or heavy rains, accident disasters such as safety incidents, public health events such as the COVID-19 pandemic, and other events that could disrupt the normal functioning of transport systems. Among them, the absorption and recovery ability of the transport system from natural disasters and accidents has been extensively studied [29,30,31], but there is less research on public health events, especially large-scale or even global ones, such as the COVID-19 pandemic.

The COVID-19 pandemic has prompted a large number of studies to understand the impact of COVID-19 on transportation. The existing research has focused on tracking the evolution of the COVID-19 pandemic and its impact on people’s mobility, road, aviation, public transport, cruise ships, and other transportation. People’s mobility and travel modes have been a widely addressed [32,33] because they directly affect transportation. Overall, the impact of COVID-19 on transportation is significant [34,35] and negative [36,37,38], which is agreed generally. Meanwhile, the existing research has also observed that (1) the impact of the pandemic on transport varies by region [39,40]; (2) external intervention in the prevention and control of the pandemic can produce positive temporal and spatial effects [3,6,41]. Among the studies on the impact of the COVID-19 pandemic on transport, the studies in the field of road transport are few, and the studies that have quantified the resilience of road transport to the COVID-19 pandemic are even fewer. The existing research has mostly analyzed the impact of the pandemic on road transport from the perspective of the external system, such as the impact of prevention and control measures on road transport during the pandemic [3,42]. Less attention has been paid to changes in the resilience of road transport systems themselves under the impact of the COVID-19 pandemic. At the same time, most of the research has been qualitative [43], while there has been less quantitative research.

On the other hand, as a guarantee for the safety and operation of the system in response to disasters/disturbances, transportation system resilience is becoming the focus of research. Resilience evaluation is mainly carried out in three stages: a conceptual framework [44], a semi-quantitative index system [45,46], and a quantitative assessment [47]. The existing works can be divided into two categories. The first category measures system resilience by comparing the difference in the functional state of the system before and after a disaster. For example, TANG et al. [48] built a timeline according to a scenario, designed the evolution process of system safety resilience of the whole process before, during, and after the disaster, and measured the safety resilience of urban road traffic systems during waterlogging disasters through system performance changes after and before the disaster. However, this assessment method is qualitative. The key indicators to measure the system’s resilience are obtained by estimation, and the results are not necessarily accurate. In addition, the dynamic change process of system resilience with disaster/disturbance cannot be reflected. In terms of specific quantification methods of system resilience, there are mainly resilience measures of transportation systems based on resilience characteristics [30,46], and resilience measures of transportation systems based on optimal models [49,50]. However, most existing methods of quantifying resilience cannot cover all stages or include all resilience capabilities, such as the absorption capacity to resist disturbances, the recovery capability, etc. Furthermore, some quantitative evaluation methods are not consistent with the concept of resilience, such as considering only the performance loss and recovery of the system, but ignoring the robustness [51]. To overcome this problem, the second category analyzes and quantifies the capabilities that help characterize a system’s resilience, such as its absorption capacity, adaptive capacity, recovery capability, etc., and these capabilities are comprehensively measured to quantify the system’s resilience [52,53]. This is a comprehensive approach to dynamically analyzing system resilience while incorporating different performance measures and characterizing resilience as a system property. For example, Guo et al. [54] used performance-based methods to analyze the airport’s strain capacity and resilience during global public health events and integrated some metrics such as aircraft movements, passenger throughput, and freight throughput in the resilience metrics model to analyze and compare the resilience evaluation under different scenarios. The results show that the resilience index can well reflect the recovery of airports under different scenarios. To take into account the dynamic evolution of the system, time-based indexes [51,55] and evaluation frameworks are often used to measure the resilience of the system.