Study On Speed And Trajectory Characteristics Of Free Left-Turning Vehicles At Main Road Intersections

As an important node of the urban road network,the intersection directly affects the road traffic efficiency.The high speed,high flow rate,and high risk of the main road intersection make it more prone to congestion and accidents.Left-turn traffic,as one of the most important factors affecting intersection capacity,has a crucial impact on improving the intersection capacity by optimizing the traffic organization,design of signs and markings,and selection of geometric parameters.Therefore,the study of the microscopic characteristics of left-turn vehicles in the turning process is of great significance.In order to clarify the operational characteristics of free left-turn vehicles at intersections,this paper selected four different types of arterial road intersections as research objects.During the traffic flow peak period,unmanned aerial vehicles were used to collect left-turn vehicle data at the above intersections,and free left-turn vehicle operation data was extracted through Tracker.Through analyzing the processed data of left-turning vehicles,it was found that the speed change characteristics of free left-turn vehicles can be divided into three stages: entry,turning,and exit.This paper conducted a detailed analysis of the speed,acceleration,and length of the speed change section in each stage,and explored the influencing factors that cause operational differences in different stages.Then,the paper discussed the influence of geometric parameters of intersections on the trajectory distribution and driving characteristics of free left-turn vehicles.At the same time,the study of the curvature characteristics of free left-turns summarized three types of trajectory curvature characteristics and analyzed the relationship between trajectory curvature and speed characteristics.Based on the above research,a trajectory model of free leftturns was established,and the model was verified by measured intersection data.The results showed that the average relative error between the calculated trajectory data and the actual value using the model was 3.81%,demonstrating the effectiveness of the model.Finally,this paper used the established trajectory model of free left-turns to optimize the design of left-turn guide lines at intersections,and used Carsim and VISSIM to compare the comfort and traffic efficiency of the optimized guide lines with circular curve guide lines by simulation verification.The results showed that the guide lines of the trajectory model of free left-turns can guide traffic flow more effectively,improve comfort and traffic efficiency compared to circular curve guide lines.The research on the speed and trajectory characteristics of free left-turn vehicles in this paper can not only provide theoretical basis for the rational design of guide lines,but also provide data support and practical guidance for the fine design of main road intersections,driver behavior analysis,traffic safety evaluation parameter revision,traffic capacity and delay calculation,and deep mining of traffic trajectory data.