A Coordinated Control Method For Traffic Signal Of Tram Network

Trams are popular in many cities as a rail vehicle that costs less than subways and has a higher volume than ordinary buses.The current theory of tram signal control is mainly focused on the green wave design of a single line,and there is a lack of consideration for the network formation of tram lines.However,with the increasing demand for public transportation,the formation of the tram network will definitely become a trend.In view of the shortcomings of the current research,the research content of this article is as follows:The tram network contains several lines.Based on the analysis of the tram driving characteristics,the Multiband model is used to establish a basic green wave model of the tram line.The model is expressed as a mixed integer linear programming problem.The green wave constraints of social vehicles,the green wave constraints of trams,and the interaction constraints of social vehicles and trams are designed according to the green wave time-space diagram.The objective function is to maximize the weighted sum of the green wave bandwidth of social vehicles.The tram network includes not only the lines,but also the interaction between the lines.The major nodes,the inner circles and the outer circles are defined.For a situation where an intersection is intersected by two lines,the network phase signal phase constraint is established based on NEMA rules;for the case where the lines form an inner circle and an outer circle,relevant constraints are derived.As the tram network becomes denser in cities,the number of constraints on the green wave model of the tram network gradually increases,especially the number of constraints on the outer circle.In order to prevent too many constraints from narrowing the range of feasible regions,the function to relax constraints are proposed,and some road sections are not allowed to have green waves.The model adds a 0-1 binary variable to each road section,indicating whether a green wave is set on the road section,and transforms the relevant road section constraints and outer circle constraints into relaxation-enabled constraints.The branch and bound method is used to solve the problem.If the value of the 0-1 binary variable of a certain road section is 1 during the optimization process,the relevant road section constraints and outer circle constraints will be relaxed,and the feasible region of the model will be expanded to obtain the global optimal solution.In order to verify the feasibility and superiority of the model,a case of a tram network was constructed.Based on the model solution and VISSIM simulation evaluation,the effect of the proposed model and other models are compared,including signal phase,phase sequence,public cycle,and phase offset at each intersection in the network.In the case of homogenized traffic volume distribution,the signal scheme of the relaxation-enabled tram network green wave model is equivalent to the tram network green wave model without relaxation function.In the case of heterogeneous traffic volume distribution,the green wave model of the tram network without relaxation function has no solution because it cannot break the circle,but the Nathan H.Gartner network green wave model can only obtain a feasible solution.In contrast,the relaxation-enabled green wave model of tram network is the best from both the analytical analysis and the VISSIM simulation evaluation analysis.The results show that the relaxation-enabled green wave model of tram network is more suitable for coordinated control of tram network signals.