| With the advantages of fast,efficient,safety,comfortable and high volume,highways are becoming progressively important in the transportation of residents.With the continuous growth of car ownership,the contradiction between supply and demand of the hignway has become prominent.At the same time,due to the obvious temporal and spatial characteristics of highway traffic flow,the high traffic density during peak periods and specific road sections has caused serious traffic congestion.Therefore,on the basis of the expansion of the highway network,it is urgent to find a scientific and effective method to optimize the control of highway traffic flow during peak periods and bottleneck sections,so that the highway remains safe,stable and unblocked.As a comprehensively used traffic management method,variable speed limit control can improve the efficiency and safety of vehicles.Existing researches on variable speed limit control have not considered the impact of lateral lane change and all adopt speed limit control that does not distinguish between lanes on multi-lane highway sections.Therefore,this paper takes highway as the research object and proposes a lane-level variable speed limit control strategy.First of all,this article briefly introduces the traffic flow operation characteristics of the basic sections and bottleneck sections of the highway,the phenomenon of reduced capacity,the definition and function of variable speed limit control,and the mechanism of influence on traffic flow.Secondly,the different states between lanes are considered.The classic METANET model is extended to the lane level,and the classic METANET traffic flow model is improved in terms of the influence of upstream and downstream road sections,the influence of ramp traffic flow,the influence of variable speed limit control and the influence of lane changing behavior.The calculation of lane change rate is based on the improved Papageorgiou lane changing model.Third,non-negative weighting coefficients and penalty coefficients are introduced to integrate the three objective functions of total travel time,total travel flow,and speed limit change into one objective function.From angles of driving safety,stability and driver comfort,set constraints on the variable speed limit value.The variable speed limit control model is established under the model predictive control framework and the optimal solution algorithm is given.Finally,the VISSIM simulation software is used to establish simulation road network based on the Shenshan Highway,and the lane-level variable speed limit control model was numerically simulated using MATLAB.Compared with the overall variable speed limit control,the improvement degree of the lane-level variable speed limit control was 5.9% and6.8% respectively.It can be seen that the control effect of lane-level variable speed limit control is further improved than that of the overall variable speed limit control.In order to further verify the effectiveness of the model,the VISSIM simulation software was re-developed based on Python and obtained a similar conclusion of the numerical simulation.At last,the results of the MATLAB numerical simulation and the VISSIM software simulation result are compared.It is found that the results of the numerical simulation and the VISSIM secondary development result are very similar.It can be considered that the multi-lane traffic flow model proposed in this paper is a good simulation of real traffic changes. |
