Research On The Coordinated Control Method For Two-Way Eight-Lane Freeway Merging Area

The increasing traffic demand leads to the normalization of congestion on some sections of the two-way eight-lane freeway.The confluence area as the source of congestion has become a bottleneck section restricting the efficiency of road traffic.In response to high-quality development of transportation,the construction of sophisticated transportation management and control technology system can effectively optimize the transportation capacity of existing facilities and alleviate congestion.Variable speed limit control and ramp metering are commonly used control technologies in the confluence area.In order to balance the right of way between the mainline and ramp,the two-way eight-lane expressway confluence area variable speed limit and ramp coordination control method would be proposed.The proposition can provide theoretical basis and technical support for the formulation of the plan and the construction of the control technology system,and has important theoretical significance and practical value for improving the efficiency and service of the freeway.Taking shanghai-nanjing two-way eight-lane expressway as an example,the detection data is sorted and extracted to demonstrate the relationship between the vehicle movement characteristics on the on-ramp,the merge location of the merge area and the traffic status of the main line.The characteristics such as the proportion,flow rate,speed and headway of vehicles of different lanes in the merging area are analyzed.Based on the basic diagram and space-time diagram of each lane under congestion,the phenomenon of capacity drop and stop-and-go is analyzed,and the critical density of each lane’s capacity drop is obtained,which provides a basis for subsequent identification of coordinated control starting conditions.The key elements of variable speed limit control are summarized,and the control strategy of variable speed limit system is clarified.The superiority of ALINEA algorithm to solve the regulation rate of single point ramp is demonstrated.Based on the model predictive control framework,the variable speed limit and ramp control are coordinated,and the coordinated control strategy of merging area is proposed.The equations of flow,velocity and density in METANET traffic flow model are analyzed and derived.The effects of variable speed limit control and ramp control on traffic state are studied respectively,and the MEATNET model is improved to establish a traffic state prediction model in merging area under the influence of coordinated control.According to the traffic flow parameters calculated by the prediction model,an optimization model of coordinated control in merging area is established to improve the overall traffic efficiency.The total travel time and total traffic volume are selected as the optimization indexes,and the constraint conditions are put forward from the change range of speed limit value of each lane,the queue length of on-ramp,the sensitivity of ramp control rate and vehicle lane changing.The genetic algorithm is selected as the solution algorithm to solve the control parameters such as variable speed limit value and on-ramp regulation rate.The coordinated control method is applied to the case based on SUMO traffic simulation.Taking the merging area of Shanghai-Naning Freeway as an example,based on the collected data,the prediction model,optimization model and simulation model are calibrated,and the validity of the model is verified.Comparing and analyzing the variation of traffic parameters of each lane under coordinated control and non-controlled conditions.The total travel time and total traffic volume are selected as traffic benefit indexes,and the environmental benefit indexes of CO,HC and NOx emissions are selected to evaluate the implementation of coordinated control method.The results show that the coordinated control method has obvious effects on alleviating traffic congestion in the merging area,improving the overall traffic and environmental conditions.It has important theoretical and practical significance on the specific plan formulation and effect evaluation of traffic control in the merging area.