Traffic Safety Evaluation Method Of Bridge Tunnel Junction Section Of Expressway Based On Traffic Simulation

As the road network in china expands,more and more highways are built across mountainous areas,where long tunnels and bridges are commonly used to overcome terrain restrictions.Sometimes,tunnels and bridges are directly connected due to extreme undulations.Such bridge-tunnel junction section often brings drivers a rapidly changing driving environment,especially in rainy and snowy weather,when the road conditions inside and outside are quite different,accompanied by crosswinds of the bridge deck.Compared with the normal road,drivers have higher driving risk when driving on a bridge-tunnel junction section.Considering the unique driving environment of the bridge-tunnel junction sections,it’s necessary to carry out traffic safety evaluation research and put forward corresponding improvement strategies,thus effectively improving the overall safety level and service capacity of highways and ensuring the smooth and efficient operation of highway network.Main researches of this paper are as follows:(1)In combination with the current research results on traffic safety of highway bridge and tunnel sections at home and abroad,this paper discusses the "four elements" of people,vehicles,roads and environment,and analyzes the potential risk factors that affect the traffic safety of highway bridge and tunnel sections.Human factors mainly consider the driver’s fatigue.The response index of simulation experiment is determined according to the vehicle dynamic performance,and the safety evaluation index system is established.(2)Considering factors such as driving speed,bridge deck crosswind,weather condition,vehicle type and road alignment,the process of v ehicles driving out of the tunnel and entering the bridge was simulated and analyzed by trucksim and Car Sim software,and the variation laws of response indexes such as lateral offset,yaw angle,yaw rate,lateral acceleration and maximum offset position of different vehicle models under different weathers were obtained.(3)The combination weighting method is used to determine the weight of each response index,and the fuzzy comprehensive evaluation method is used to calculate the comprehensive risk value under multiple scenarios and divide the safety risk level.Based on response surface methodology,the traffic safety risk prediction models under different vehicle types,road alignments and driver types are established.The results show that the driving speed is the most important factor affecting the driving safety,followed by the weather conditions,and the influence of the cross wind on the bridge deck is the lowest;When the driver is tired and drives a large vehicle through the straight bridge tunnel junction section,the impact of the bridge deck crosswind on driving safety will be higher than that of the weather.(4)Based on the analysis of several risk factors of bridge-tunnel junction section and determinations of safe speeds under different wea ther conditions,the traffic safety of bridge-tunnel junction section of Mianchi Luoning highway in Henan Province was researched.The risk zoning map of large and small vehicles in sunny,rainy and snowy days were made,and the distribution of driving risk level was defined,thus providing technical support for formulating dynamic speed limit strategy,as well as theoretical and application value for highway driving safety.Based on the traffic simulation technology,this paper establishes the traffic safety evaluation index system of the bridge tunnel junction section of expressway,carries out the traffic safety simulation experiment,and puts forward the traffic safety evaluation method for the bridge tunnel junction section of expressway.The proposed traffic safety assessment process for bridge tunnel junction section considers human factors on the basis of existing safety assessment specifications,provides a theoretical basis for the formulation of Safety Assessment Specifications for bridge tunnel section,and can carry out risk assessment and provide dynamic speed limit strategy for the bridge tunnel junction section of new expressway lacking historical accident data,which has theoretical and engineering practical significance.