Optimal Design Of The Length Of Acceleration Lane In Merging Area Of Highway Under Mixed Heterogeneous Traffic Flow

The merging area in highway is used as a transition section for ramp vehicles to enter the highway.Vehicles need to frequently change speed and lane to complete the merging of traffic flow.Therefore,the vehicle operation characteristics of the merging area are more complicated than other road sections.At present,most studies on merging areas in highway are based on the traditional traffic flow environment.With the continuous development of automation technology,a number of intelligent vehicles with autonomous driving functions have begun to appear on the road.It is expected that for a long time in the future,as the transition stage from traditional vehicles to autonomous vehicles,intelligent vehicles will share the road with traditional vehicles,and a mixed heterogeneous traffic flow composed of intelligent vehicles and traditional vehicles will be formed on the road.To this end,this article explores the length of the accelerating lanes in the merging area suitable for the operation characteristics of mixed heterogeneous traffic flows.Based on the Shaanxi Provincial Natural Science Program Project "Research on Acceleration Lane Length of Intelligent Expressway in Heterogeneous Traffic Flow with Manual-Automatic Vehicles"(Project No.: 2020JM-222),this paper explores the length of acceleration lane that meets the safety,efficiency and stability of mixed heterogeneous traffic flow at different design speeds of main lines.First of all,through statistical analysis of the type of merging areas of Xi’an Ring Expressway,the type of merging area to be studied is determined,and the research scope of the merging area is defined.Using the Simi Motion extraction of video data and use MATLAB wavelet toolbox to eliminate the trajectory error from traffic flow,analyze the characteristics of traffic flow operation from four aspects: traffic volume,vehicle speed,headway and the number of traffic conflicts.Secondly,the traditional vehicle model is calibrated and verified according to the results of the characteristic analysis,and the car-following model and lane-changing model parameters of the intelligent vehicle are improved based on the safe calculation of the vehicle lane change.Then,a micro traffic simulation software SUMO was used to realize the mixed heterogeneous traffic flow simulation,and the adaptability of the acceleration lane length in the current specification of highway merging area to the mixed heterogeneous traffic flow was explored.Finally,based on the principle of probability theory,a probability calculation model for ramp vehicles can be established,and then the acceleration lane length calculation model is derived.The acceleration lane length is optimized and verified,and it is used in other different main line design speed situations.The results show that the market penetration of the intelligent vehicle has a significant influence on the operation of the mixed heterogeneous traffic flow,and the length of acceleration lane in current specification in terms of efficiency and stability can better applicable to mixed heterogeneous traffic flow,but cannot fully apply in terms of safety,and the optimized length of acceleration lane made up for the lack of security.The optimal design values of the length of the acceleration lane corresponding to different design speeds of the main line are as follows: when the design speeds of the main line are 60km/h,80km/h,100km/h and 120km/h,the optimal design values of the length of the acceleration lane corresponding to the main line are 170 m,200m,220 m and 255 m.