Abstract: In order to meet the development needs of highly automated driving on freeways, taking off-ramp lane changes on freeways as a research scenario, an off-ramp lane-changing timing decision making model for intelligent connected vehicle platoons (ICVPs) on freeways based on the number of fitted gaps was proposed, to address the problem when vehicle platoons changed lanes before entering exit ramps. Firstly, probability distributions of the number and length of gaps were established, and based on this, the number of fitted gaps was estimated. The number of fitted gaps contained in search space was accumulated by continuously expanding it, the shortest search distance was estimated according to the level of the number of fitted gaps. Secondly, the probability distribution of lane-changing distance was established, and reasonable lane-changing distance was defined as lane-changing distance corresponding to a suitable percentile. Then, based on the shortest search distance and reasonable lane-changing distance, an optimization model for the shortest reserved distance was established to realize lane-changing timing decision-making for vehicle platoons. Finally, by conducting comparative experiments, the operability and feasibility of the proposed model were verified. Simulation analysis results show that compared to the method in which the platoon starts searching for gaps and changing lanes as soon as it enters roads, the lane-changing success rate of both above models is on par when the number of vehicles in the vehicle platoon is 2, and when the number of vehicles in the platoon is 4, the lane-changing success rate of both models increases by 82%. Compared to the method in which the platoon starts searching for gaps and changing lanes when vehicle platoons approach the allowed lane-changing termination position, when the number of vehicles in the platoon is 2, the distance from the lane-changing position of the two models to the allowable lane-changing termination position is reduced by 61% and 43% respectively; when the number of vehicles in the platoon is 4, the distance from the lane-changing position of the two models to the allowable lane-changing termination position is reduced by 19% and increased by 37% respectively. Therefore, compared to lane change without lane-changing timing decision making for vehicle platoons, lane change with lane-changing timing decision making for vehicle platoons can effectively balance lane-changing success rate and distance from lane-changing position to the allowed lane-changing termination position.

Key words: traffic and transportation engineering; lane-changing timing decision making; mathematical modeling; intelligent connected vehicle platoons; off-ramp lane change; fitted gaps

摘要： 为迎合高速公路高度自动驾驶的发展需要，以高速公路出匝换道为研究场景，针对车队在驶入出口匝道前何时换道的问题，提出一种基于合适空隙数量的智能网联车队高速公路出匝换道时机决策模型。首先，建立空隙数量与长度的概率分布，在此基础上，估计合适空隙数量，通过不断拓展搜索空间的方式积累其中包含的合适空隙数量，根据合适空隙数量的水平估计最短搜索距离；其次，建立换道距离的概率分布，以一个合适分位数对应的换道距离定义合理换道距离；然后，在最短搜索距离与合理换道距离基础上，建立最短预留距离的最优化模型，以此实现车队换道时机决策；最后，通过设置对比实验，验证模型的可操作性与可行性。仿真分析结果显示：相较于车队进入道路就开始搜索空隙并换道的方式，当车队车辆数为2时，2个模型的车队换道成功率持平；当车队车辆数为4时，2个模型的车队换道成功率均升高了82%；相较于车队邻近允许换道终止位置才开始搜索空隙并换道的方式，当车队车辆数为2时，2个模型的车队换道位置至允许换道终止位置的距离分别缩短了61%与43%；当车队车辆数为4时，2个模型的车队换道位置至允许换道终止位置的距离分别缩短了19%与增加了37%。综上，相较于无车队换道时机决策下的车队换道，车队换道时机决策下的车队换道能有效兼顾换道成功率与换道位置至允许换道终止位置的距离。

关键词: 交通运输工程；换道时机决策；数学建模；智能网联车队；出匝换道；合适空隙