基于无人机视频拍摄的高速公路小型车换道行为特性

为了研究高速公路小型车的换道行为特性，采用2台无人机同时在200 m的高空对交通流进行拍摄，获取交通流运行状态。构建拍摄路段的高精度地图，获取每一时刻车辆的精确运行状态数据，在此基础上对2个视频进行拼接，最终获得车道位置、速度、车辆编号等8项关键指标，共提取换道行为1 520条，筛选后得到完整的自由换道数据942条。采用车辆轨迹是否持续偏移作为判断换道行为起终点的依据，在此基础上分析换道的时间长度、空间长度、与周边车辆的相互状态以及换道行为的安全性等16个特征参数。得出平均换道时间长度为6.09 s，平均换道空间距离为148.08 m，换道时间与空间长度均符合对数正态分布。换道车辆与目标车道后方车辆的平均距离最小（34.29 m），其相对距离在10 m以内的占28.24%，驾驶人为了加快行驶，在与目标车道后方车辆相对距离较小的情况下，依然采取换道措施。与正前方车辆的相对速度差最大，平均值为10.2 km·h^-1，并且在83%的情况下，本车的速度大于前车，说明车辆自由换道是由于前方车辆行驶速度较慢所引起。采用TTC，MTC分别对换道起始时刻的安全性进行分析，并将安全状态划分为4种类型：严重-紧急状态、严重-非紧急状态、非严重-紧急状态、非严重-非紧急状态。其中严重-非紧急，非严重-非紧急这2种状态占比最高。该研究成果对了解中国驾驶人在高速公路上的换道行为特性，以及对建立适用于中国实际交通环境特征的换道行为模型具有一定参考意义。

Analysis of Lane Change Behavior of Passenger Cars on the Freeway Using UAVs

To study the discretionary lane change behavior of passenger cars on the freeway, two UAVs (Unmanned Aerial Vehicle) were used to simultaneously shoot videos at a height of 200 m. Also a high-precision map was constructed. The two videos were spliced and the accurate running states of vehicles at each frame were obtained, including 8 key indicators, such as lane position, speed, and ID of the vehicle. A total of 1 520 lane change behaviors were extracted and 942 discretionary lane change behaviors were obtained after screening. Determination of the start and end of lane-changing was based on whether the trajectory of the vehicle continued to deviate. On this basis, 16 characteristic parameters, such as the length of lane-changing time, length of space, mutual state with surrounding vehicles, and safety of lane change behavior, were analyzed. It is concluded that the average length of lane-changing time is 6.09 s and the average space distance of lane-changing is 148.08 m. A lognormal distribution provides the best fit to the time and space length of lane-changing. The average distance between the lane-changing vehicle and the following vehicle in the target lane is found to be the shortest (34.29 m). The relative distance within 10 m is found to be 28.24%. To speed up driving, drivers make the lane-changing decision when the relative distance between the lane-changing vehicle and the following vehicle in the target lane is small. The relative velocity difference between the subject vehicle and the preceding vehicle in the original lane is the largest, at an average of 10.2 km·h^-1. Moreover, in 83% of cases, the speed of lane change car is faster than that of the front car in the original lane. It is fully explained that the free lane change of vehicles is caused by the slow speed of the vehicles ahead. TTC (time to collision) and MTC (margin to collision) were used to analyze the safety state at the beginning of lane change. The safety state can be divided into four types:serious-urgent state, serious-non-urgent state, non-serious-urgent state, and non-serious-non-urgent state. The two states serious-non-urgent, non-serious-non-urgent account for the highest proportion. The results of this research provide a certain reference for understanding the characteristics of the lane change behavior of drivers on freeway in China. The research results also have certain reference values that can be used in the establishment of a lane change behavior model suitable for the actual traffic environment in China.