Research On Driving Safety Risks And Management Strategies Of Expressway Traffic Affected By Low-Speed Vehicles

China’s expressway traffic composition is complex and diverse,with low-speed vehicles occupying a certain proportion.When mixed with other vehicles,low-speed vehicles will cause interference with other vehicles so that other vehicles can not be in accordance with the established speed,easily lead to disruption of the expressway traffic flow,reduce the efficiency of vehicle travel,and generate traffic safety risks.Therefore,the research on the safety risk characteristics of the expressway under the influence of low-speed vehicles is beneficial to improve the expressway’s safety condition and building a safer expressway system.In this paper,we construct a vehicle queuing and dissipation model under the influence of low-speed vehicles with the help of microsimulation technology using nonlinear fitting and study the distribution law of vehicles under the influence of low-speed vehicles with traffic density and average speed as indicators.Meanwhile,time-based indicators TTC and PET,kinematic-based indicators Max S,Delta S and Max D and statistical-based indicator P(UEA)are selected to construct a conflict evaluation model based on SSAM and analyze the conflict characteristics among vehicles under the influence of low-speed vehicles.The results show that the greater the driving speed of low-speed vehicles,the smaller the influence range,and the evolutionary trends of traffic density and average speed of their lanes can be described by Gaussian and exponential functions,respectively,reflecting the existence of spatial heterogeneity of vehicle distribution under the driving speed of different low-speed vehicles.In addition,regarding inter-vehicle conflicts,the outer lanes are most affected by low-speed vehicles,with the highest total number of conflicts,the highest probability of accidents,and the most significant traffic safety risks.Considering the special characteristics of low-speed vehicles in terms of driving speed and body structure size,the model of fast road driving safety risk field is constructed,including dynamic and static driving safety risk fields as well as lane driving safety risk field,and the difference of driving safety risk field generated by low-speed vehicles and ordinary vehicles is studied from the risk field influence range and field strength level.Through the analysis of typical scenarios,it is found that the risk field generated by low-speed vehicles has a larger influence range than that of ordinary vehicles,and the smaller the relative distance,the larger the field strength,and the field strength approaches the peak at the point close to the edge of the vehicle.At the same time,when two adjacent lanes have low-speed vehicles driving,the risk field has a superposition effect,which will further expand the impact range of the risk field generated by low-speed vehicles.From the starting point of other vehicles,to safely avoid low-speed vehicles and reduce the risk of collision,we construct a vehicle lane change decision model based on the Nash game,introduce an ordinary vehicle driving behind a low-speed vehicle as the subject vehicle,give the game gain matrix between the subject vehicle and the vehicle behind the target lane as well as the speed,safety and efficiency gain functions of the model,and get the best lane change starting point when the subject vehicle faces the low-speed vehicle in front of it.At the same time,the vehicle path planning model based on the risk field of traffic safety is constructed.The safe lane change path is obtained using Newton’s iterative method through the equilibrium equation of the subject vehicle in the risk field,and finally,the above two models are integrated to propose the vehicle lane change path management strategy under the influence of low-speed vehicles.The effectiveness of the above strategy is demonstrated through the analysis of typical scenarios,showing that the strategy can be used in the future intelligent networked environment.