Research On The Emergency Rescue Vehicle Path Planning Method Based On Safety Evaluation Of Road Network Nodes

In recent years,the frequent occurrence of emergencies such as COVID-19,natural disasters and human accidents has brought huge losses to human life and property,and seriously affected the stability of social order and economic development.To quickly control the negative impact of sudden accidents,emergency rescue vehicles must deliver rescue teams and materials to the scene at the fastest speed under the interference of uncertain factors such as dynamic traffic environment and traffic congestion,to ensure the safety of the lives and property of the injured and stabilize the order of the scene.However,affected by various subjective and objective factors of road traffic,emergency rescue vehicles often encounter traffic accidents at the intersections of network,which seriously threatens the lives of rescue teams and patients,and easily leads to the rescue failure.To make the emergency rescue more safe and reliable,this paper considers the priority characteristics of emergency rescue vehicles,studies the traffic safety evaluation model of signalized intersection and expressway merging area in the emergency scene.The safety factors are introduced to propose a timing co-evolutionary path planning method of emergency rescue vehicle under the dynamic road network.This study aims to improve the driving safety of emergency rescue vehicles as much as possible,while their travel efficiency is always given a primary consideration.Moreover,to further enhance the driving safety level of emergency rescue vehicles,this paper proposes an instantaneous risk identification method for the optimal path of emergency rescue vehicles,dynamically monitors the driving risk in the process of traveling along the optimal path,and selects reasonable warning parameters and methods to assist emergency rescue vehicles to avoid danger.The research work is as follows:(1)The safety evaluation of signalized intersection in an emergency scenario is studied.The distribution of longitudinal arrival and lateral deviation of vehicles at signalized intersections are analyzed.Combined with the characteristics of random arrival and priority of emergency rescue vehicles,a vehicle conflict probability model based on phase design is established.According to the conflict probability threshold,the safety levels of the grid are classified to construct the emergency safety evaluation model of signalized intersections.The effectiveness of the proposed model is verified by using the actual data,VISSIM and SSAM simulation software.Taking the signalized intersection of Wushan road and Yuehan road in Tianhe District of Guangzhou as a case study,the safety status of the intersection under nonsignalized strategy,signal timing optimization strategy and flow control strategy are analyzed.The emergency safety evaluation model of signalized intersection provides node risk data for the path planning of emergency rescue vehicle.(2)The safety evaluation of the expressway merging area in an emergency scenario is studied.This paper explores the operation characteristics of traffic flow on main roads and ramps,and establishes the longitudinal arrival probability model of vehicles according to three traffic flow states.Considering the traffic composition,actual vehicle size,lane width,acceleration lane length and other parameters,the probability model of lateral deviation on main roads and the probability model of lane change on-ramps are established.Then,this study introduces the random interference term of emergency rescue vehicle to construct the vehicle conflict probability model.Furthermore,an emergency safety evaluation model of expressway merging area is proposed by integrating the conflict probability model and kinetic energy loss model.Finally,the effectiveness of the proposed model is verified by experimental analysis.Based on the actual traffic data of the merging area,the internal relationship between the safety status of the merging area and the speed and flow of that is explored to give the speed and flow control suggestions from the aspect of traffic safety optimization.The emergency safety evaluation model of the expressway merging area can provide node risk data for the path planning of emergency rescue vehicle.(3)This paper studies the path optimization problem of emergency rescue vehicle based on the safety evaluation model of network nodes in a dynamic network.This study analyzes the disturbance effect of traffic environment uncertainty on path planning,and considers the demand of path planning of emergency rescue vehicles for traffic safety and travel efficiency.Based on the node safety evaluation model of the urban network,a timing co-evolutionary path optimization method considering the priority characteristics of emergency rescue vehicles and traffic congestion avoidance is proposed.Moreover,an improved ripple spreading algorithm is designed to solve the model.Finally,the control variable method is used to design the simulation experiment,which highlights the advantages of the proposed method in optimizing the travel time and improving the safety level of the rescue path.The path planning method in this paper can select the path scheme and driving environment for the instantaneous risk identification of the optimal path for emergency rescue vehicles,and assist the emergency rescue vehicles to arrive at the scene safely and quickly.(4)The instantaneous risk identification of the optimal path for emergency rescue vehicles is studied.This study analyzes the potential risk factors in the process of emergency rescue vehicles driving along the path planning scheme.The interactive game relationship between emergency rescue vehicles and surrounding vehicles in two typical driving states is comprehensively considered.According to the vehicle operation condition,the temporal risk and spatial risk evaluation indexes are extracted.Then,the temporal and spatial risks of vehicle are deduced by using fault tree analysis.Based on this,the instantaneous risk identification models of the optimal path for emergency rescue vehicles under the car following state and lane changing state are proposed,respectively.Finally,the identification accuracy of different risk warning parameters is analyzed by using the vehicle trajectory data.The risk conversion relationship between emergency rescue vehicles and social vehicles is proposed to determine the warning thresholds and warning mode of the instantaneous risk.The experimental results show that the model can quickly and accurately identify the dangerous driving scenes,and provide theoretical support for the early warning of emergency rescue vehicles.Through the research on the above problems,it further enriches the relevant theories of traffic safety evaluation,the path planning of emergency rescue vehicle and its driving risk identification.This study can improve the drawbacks in the existing emergency rescue decision management,enhance the travel efficiency and driving safety of emergency rescue vehicles,and provides auxiliary decision support for the path selection of emergency rescue action.