城市干路交叉口右转车辆轨迹流线与曲率特性分析

为明确城市干路交叉口汽车右转的轨迹特性和轨迹曲率模式，使用无人机在重庆市4个城市道路交叉口上方进行高空拍摄。利用图像分析方法采集了右转车辆的轨迹数据，包括时间、行驶速度和轨迹坐标等，通过对相邻轨迹点外接圆半径的计算得到轨迹曲率。运用轨迹线-车道边缘线的间距值分析了右转车辆轨迹通过位置分布与交叉口几何布局之间的关系，明确了交叉口右转车辆轨迹的曲率特性。运用聚类方法识别了右转车辆的6种轨迹曲率形态，确定了不同轨迹曲率形态下的常见驾驶行为，并研究了车辆行驶速度与轨迹曲率的相关关系。研究结果表明:①交叉口几何布局（包括路缘半径、车道宽度和出口车道数）对右转轨迹通过位置分布存在影响；②带渠化设计的右转专用道可以限制轨迹分布范围，减少右转交通的冲突和延误；③在右转过程中公交车辆较小型汽车所需侧向空间更大，轨迹分布的离散程度更低；④轨迹曲率的关键点与圆曲线设计中的主要点变化趋势不一致；⑤车辆加速度与轨迹曲率变化率呈负相关关系，相关系数为-0.843 5；⑥行驶速度与等效半径存在正相关关系，车辆行驶速度越快，圆曲线内轨迹的等效半径越大。 

An Analysis of Trajectory Streamline and Curvature Characteristics of Right-turn Vehicles at Urban Arterial Road Intersections

A drone was used to take high-altitude images of four urban road intersections in Chongqing to study the trajectory characteristics and curvature patterns of right-turn vehicles at urban arterial road intersections. The trajectory data of right-turn vehicles, including time, driving speed, and trajectory coordinates, are collected by using image analysis methods, based on which the trajectory curvature of vehicles is obtained by calculating the radius of circumcircle of adjacent trajectory points. The relationship between the distribution of passing positions of right-turn vehicles and the geometric layout of intersections is analyzed by using the distance between the trajectory line and the curb line, and the trajectory characteristics of right-turn vehicles at the intersections are further studied. Six types of curvature patterns of the trajectories of right-turn vehicles are identified based on a clustering method, and common driving behaviors under different curvature patterns are determined, and the relationship between vehicle speed and trajectory curvature is finally investigated. The results reveal the following conclusions. ① The geometric layout (including the curb radius, lane width, and the number of exit lanes) has impacts on the distribution of trajectories of right-turn vehicles. ②Right-turn lanes with channelized design can limit the distribution of trajectories and reduce conflicts and delays in right-turn traffic. ③ During a process of right-turning, more lateral space is required by buses than by cars, and the distribution of trajectories is less discrete. ④The key points of trajectory curvature are inconsistent with the trends of the main points in the circular curve design. ⑤ The acceleration of a vehicle has a negative correlation with the change rate of the trajectory curvature, and the correlation coefficient is －0.8435. ⑥ The driving speed has a positive correlation with the equivalent radius: the faster the vehicle moves, the larger the equivalent radius of the trajectory in the circular curve.