| In the permissive left-turn phase intersection,there are inevitable conflicts in time and space between left-turn vehicles,straight vehicles and pedestrians crossing the street,and traffic safety issues are very prominent.Although our national road traffic safety law provides that left-turn vehicles should give way to straight vehicles,in fact,it does not work,left-turn vehicles often have complex and changeable movement state.Therefore,this paper studies the movement characteristics of left-turning vehicles at the permissive left-turn phase intersections and the driving safety are analyzed from the microscopic level,the research content as follows:(1)This study uses drones to collect data from four intersections in Xi’an,and the vehicle trajectories information is excavated by the video analysis software George 2.1 as basic data.According to the behavior of the left-turn vehicle interacting with the opposite straight vehicle,the left-turn vehicle turning behavior is divided into three modes: rush mode,yield mode and no interference mode.This paper analyzes the trajectory distribution under different traffic behaviors from two aspects: The variation of single vehicle driving direction and the clustering of multi-vehicle turning position.According to the speed characteristics of left-turn vehicles,the characteristics of speed and acceleration in the conflict area between left-turn vehicles and straight vehicles are analyzed emphatically.(2)On the basis of analyzing the movement characteristics of left-turn vehicles,a method of traffic safety analysis for left-turning vehicles is proposed.From the perspective of vehicles,three evaluation indexes,driving speed difference,speed variation and minimum deceleration,which reflect the variation of single vehicle speed,are selected to construct the vehicle driving safety grade judgment model based on entropy weight-vague compound matter-elemen;From the spatial perspective of intersections,the intersection is divided into three regional segments,and three evaluation indexes,velocity variation coefficient,standard deviation of acceleration and standard deviation of jerk,which reflect the degree of velocity dispersion of the regional segment,are selected to construct the regional segment driving safety assessment model based on entropy weight-TOPSIS method,and analyzes the traffic safety of left-turning vehicles at the intersection of science and technology fouth road and Tuanjie south road(3)On the basis of analysis of the existing traffic conflict indexes,the Post Encroachment Time is used to divide the conflict severity between straight vehicle and left turning vehicle into four categories: no conflict,minor conflict,medium conflict and serious conflict.The regression prediction mode of the severity of straight-left turn vehicle conflict was established by analyzing the factors related to the severity of straight-left turn vehicle conflict as independent variables.The results show that left-turning vehicle arrival speed,the turning behavior mode,signal stage,average headway and average speed difference have significant influence on the severity of straight-left turn vehicle conflict.And the model can be used to predict the probability of straight-left turn vehicle conflict in different severity.(4)According to the operating characteristics of left-turning vehicles in the permissive left-turn phase intersection and the analysis results of driving safety,this paper put forward measures to improve the driving safety of the intersection.Taking into account factors such as vehicle trajectory,secondary crossing facilities,left-turn guide line application range,etc.,a left-turn guide line model applicable for the design stage was constructed;from the traffic management and control stage,the speed control method and phase optimization scheme of intersection are put forward respectively to improve the disordered driving environment of the permissive left-turn phase’s intersection and provide reference for related traffic management departments. |
