| The implementation of timely and effective traffic flow control after highway accidents can alleviate the degree of road network congestion caused by accidents.The traditional traffic control at the scene of accidents cannot accurately transmit accident information to upstream vehicles,which makes the traffic flow frequently change lanes,thus reducing traffic efficiency and even causing secondary accidents.The mixing of CAV vehicles provides more means for traffic warning and control in the future man-machine mixed driving scenario.In this paper,the multi-lane expressway after the accident is taken as the research scene,and the accident warning lane change of mixed traffic flow and the cooperative lane change promoted by the fleet are explored,which provides theoretical guidance and practical reference for improving the traffic flow operation quality in the upstream of the expressway accident handling operation area in the future vehicle networking environment.Firstly,the basic characteristics of traffic accidents on expressways and the types of lane closures caused by accidents with different numbers of lanes are introduced.The development stage of accidents and the formation and dissipation of congestion are analyzed and demonstrated from the time dimension.The impact of accidents on the maximum capacity of expressways and the changes in the running state of vehicles before the accident area are discussed.Combined with the traffic flow following theory and the basic graph model,the characteristics of human-machine mixed driving traffic flow are analyzed theoretically.Then,based on the Gipps model and the ACC and CACC car-following models calibrated by PATH laboratory,the cellular automaton model of mixed traffic flow is constructed.On this basis,the accident and two-lane lane change scenarios are introduced.According to the driving characteristics of different vehicles in the accident area,the accident-affected sections are divided,and the tendency and mandatory lane change rules of artificial vehicles are established.At the same time,the accident warning area is set up,and the CAV warning lane change strategy under this area is proposed with the goal of guiding the vehicle to merge to the non-accident lane in advance.The simulation is carried out by introducing parameters such as strategy implementation rate,flow level,and length of accident warning area.The results showed that the traffic capacity in the bottleneck area increased with the increase of the implementation rate of the early warning lane change strategy.When the implementation rate reached 40%-60%,Traffic capacity is improved by about 13%-38%,and the optimization effect is more significant at low and medium flow levels.Finally,based on the characteristics that the orderly arrangement of CAVs under the same permeability can improve the road capacity,a lane-changing category considering the change of CAV fleet strength is proposed.At the same time,by introducing a threelane highway scenario where the accident leads to the closure of the outer lane,a cooperative lane-changing strategy is constructed on the basis of fleet facilitation,which guides the CAV of the middle lane to merge with the non-accident lane on the other side,and gives up the lane-changing space for the CAV of the accident lane to complete the cooperative lane-changing,so as to improve the strength of the automatic driving fleet on the accident section and guide the CAV to transfer to the non-accident lane as soon as possible before reaching the accident area to efficiently pass through the bottleneck area.The effectiveness of the proposed strategy is verified by simulation,in the three-lane scenario,the collaborative lane change strategy adopted by CAV is superior to the earlywarning lane change strategy in optimizing traffic flow under different traffic levels and CAV permeability,and the advantage becomes more obvious with the increase of the implementation rate of the strategy. |
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