车路协同下避让紧急车辆协同换道策略

为加快紧急车辆抵达事故现场的速度，同时减少紧急车辆优先权对其他车辆的影响，运用车路协同系统，提出避让紧急车辆协同换道策略，通过调整紧急车辆下游车辆位置，实现紧急车辆高效通过路段。以紧急车辆前车（DV）及其相邻目标车道车辆为控制对象，根据相邻车道车辆间距与车车通信范围，搜索DV可换道空间间隙集。以交通流整体恢复稳定时间最小为目标，确定DV换道轨迹和相邻车道协作车辆的速度变化，引导车辆完成协同合流，既能保障车辆安全换道，还能降低换道造成的速度振荡传递。同时，为快速恢复DV换道造成的目标车道车辆速度波动，对上游车辆（UV）采取先进先出规则的换道控制策略。所提协同避让紧急车辆的策略考虑了车辆协同换道对交通流的整体影响，并在原有换道策略的基础上提出了减少速度波动传递的控制方法。案例分析结果表明:采用上下游协同换道策略最短换道时间为6s，此时紧急车辆距前车78.66 m时发送避让信号。同时研究发现，恢复交通流速度稳定所需的时间为29 s，比未采用上下游协同换道策略降低了34%。 

A Cooperative Lane Changing Strategy to Give Way to Emergency Vehicles with the Cooperative Vehicle Infrastructure System

A cooperative lane-changing strategy is proposed to reduce the time loss when emergency vehicles approaching to accident scenes, and reduce the impacts of emergency vehicle priority on other vehicles with the cooperative vehicle infrastructure system (CVIS). By adjusting the position of the downstream vehicles (DV), the emergency vehicles can efficiently pass the road sections. The DV and vehicles in the adjacent target lane are taken as control objects. A space-gap set for lane-changing of DV is determined according to the spacing and communication range of vehicles in adjacent lanes. Further, aiming to minimize the overall recovery time of traffic flow, the lane-changing trajectory of DV and the speed change of cooperative vehicles in the adjacent lanes are determined to guide vehicles to complete cooperative merging. It can not only guarantee the safety of the lane-changing behaviors, but also reduce the transmission of speed fluctuations caused by the lane-changing behaviors. For upstream vehicles (UV), the rule of first-in-first-out (FIFO) is used to reduce the time for recover from the speed fluctuations caused by lane-changing behaviors of DV. Considering the impacts of lane-changing on the traffic flow, a control method to reduce the transmission of speed fluctuations is proposed based on a classic lane changing strategy. The results of a case study show that the shortest lane-changing time is 6 s when using the proposed cooperative lane-changing strategy, and the corresponding distance of sending emergency signal is 78.66 m. Meanwhile, the results show that the time required to restore stability of speed is 29 s, which is 34% shorter than that without the cooperative lane-changing strategy.