## 2 Road Operational Resilience
### Analysis of Road Operational Resilience Elements  
Road operational resilience is related to the environment, road, and facilities (such as the robustness of pavement performance, the robustness of lane access, and the robustness of facility functions). To more clearly depict road operational resilience, this paper proposes a hierarchical framework of road operational resilience elements based on PSR theory, as shown in Figure 1.  
The pressure resilience dimension is characterized using exposure, uncertainty, diversity, and hazard factors related to pressure:  
* The exposure to pressure characterizes the possibility of the road system being exposed to risk scenarios. The higher the exposure, the greater the possibility of disturbance. Specific elements include the exposure to meteorology (E1-1), the exposure to road type (E1-2), and the exposure to traffic flow (E1-3);
* The uncertainty of pressure characterizes the randomness of the time, type, and degree of emergency events on roads. The higher the uncertainty of pressure disturbance, the lower the pressure resilience performance, and the higher the difficulty for road systems to defend against disasters. Specific elements include the diversity of accident types (E2-1) and the diversity of vehicle types (E2-2);* The diversity of pressures characterizes the possibility that road systems face various types of risks. Under the influence of other external factors, such as complex road environments and vehicle conditions, various disturbances may occur in a coupled and spread manner, increasing the risk of impact. Specific elements include uncertainty of scattered objects (E3-1) and uncertainty of fire (E3-2);
* The risk impact on road emergency occurrences is characterized by the pressure hazard, which includes losses of facilities, personnel, and vehicles. Specific elements include the hazards to the vehicle involved (E4-1), the hazards to casualties (E4-2), and the hazards to the facility (E4-3);  
This paper measures the state resilience dimensions based on state robustness and state redundancy factors;  
* The state of robustness is the ability of a road system's inherent properties to resist disturbances, such as physical properties and network topology properties. Specific elements include the robustness of road width (E5-1), the robustness of road maintenance (E5-2), the robustness of pavement performance (E5-3), the robustness of lane access (E5-4), and the robustness of facility functions (E5-5);
* The state redundancy maintains functions through its replaceable components in response to damaged traffic functions. It is generally characterized by the storage capacity and substitutability of resources required by road systems, such as the redundancy of design traffic capacity (E6-1) and the redundancy of road network connectivity (E6-2). This paper describes response resilience through response awareness, resourcefulness of response, rapidity of response, and responsive learnability:  
* Response awareness characterizes the timeliness and accuracy of perception for emergency events and risk environments. It is a prerequisite for response occurrence and can be characterized by the rapidity of response arrival (E7-1);
* Rapidity of response refers to the ability of transportation system managers to take emergency disposal measures to restore system functions quickly. It usually manifests itself as effectiveness and speediness in emergency disposal. Specific elements include the implementability of response disposal (E8-1) and the rapidity of response disposal (E8-2);  
Figure 1: Hierarchical framework of road operational resilience elements based on PSR theory. * The resourcefulness of the response is measured by managers' ability to organize transportation systems to establish priorities and mobilize various disaster prevention and mitigation resources. It is the basis for response disposal.