Optimization Of Tram Timetable Under The Semi-exclusive Right-of-Way Mode

With the rapid expansion of urban population and the continuous improvement of motorization,road traffic congestion has become an important challenge for large cities.With the concept of green and smart city construction and the strategy of prioritizing public transport,tram has attracted a great attention for its advantages of low cost,energy conservation and environmental protection.And how to maximize trams' potentials in their flexibility,rapidity and reliability is an important issue to study.In China,modern trams typically operate on semi-exclusive right-of-ways.Although tram lanes isolate trams from other traffic in the running sections,the operation is largely affected by signal control at intersections where trams share the same right-of-way as general traffic.Now,there are relatively few systematic researches on the professional standards,technical specifications and operation practices of trams in our country.Therefore,to ensure the operation efficiency and improve the operation service level of tram,it is necessary to study timetable optimization for tram lines by effective operation time adjustment in combination with the characteristics of signal control.Based on previous researches,this study analyzes the complexity of the entire operational process,and puts forward the optimization method of tram timetable by considering the signal control conditions.From the perspectives of no-signal priority,active signal priority,and passive signal priority,the timetable optimization models for trams are constructed respectively.The main research contents and conclusions are as follows:(1)Taking the tram line with no-signal priority as the research scenario,based on the analysis of the complexity of the tram operation in sections,the constraints of tram operation time,dwell time,intersection running state,headway are considered.And the tram timetable optimization model under the condition of no signal priority is constructed,taking the tram travel time,dwell time increment and the minimum number of stops as the objectives.According to the characteristics of the model,the fuzzy mathematical programming method is proposed to transform the original multi-objective problem into the single objective optimization problem.The validity of the model is verified by case analysis,and the sensitivity analyses of the upper limit of dwell time increment and departure interval offset are carried out.The results show that adjusting the section running time and extending the dwell time of the tram can effectively reduce the total travel time and the number of stops at intersections;extending the dwell time and relaxing the headway offset constraint can effectively improve the tram's running efficiency.(2)Taking the tram line with active signal priority as the research scenario,based on the control rules of fixed cycle active signal priority,this paper proposes a two-way tram timetable optimization method which is suitable for the active signal priority strategy.Considering the constraints related to tram operation and signal priority strategy,the timetable optimization model with active signal priority is constructed to minimize the travel time,dwell time increment and the negative impact on intersection operations.According to the nonlinear and multi-objective characteristics of the initial model,the linearization method is given in this paper.For obtaining a timetable with an equal satisfaction for the three objectives,the fuzzy mathematical programming approach is adopted to transform the problems into mixed integer linear programming(MILP)problems.The validity of the model is verified by a case.The absolute signal priority and no-green insertion strategy are used for comparative analysis.The results show that the proposed optimization model can both improve the operational efficiency of trams and reduce the negative impact on intersections.Finally,the sensitivity analyses of dwell time increment,departure interval offset and the fixed penalty of signal priority are carried out.(3)Combined with the characteristics of the tram line,the passive signal priority is considered.Based on the analysis of the existing PM-BAND model,the model description method of phase sequence adjustment and tram turning are integrated,and the relevant operation conditions of tram and car are considered.Considering the optimization objectives of trams and cars,a timetable optimization model with passive signal priority is constructed.The empirical results show that the model can both effectively improve the service level of trams,and achieve an adaptive division of the green wave.Compared with the MAXBAND model and the method of "first optimize the sub area,then optimize the timetable",the proposed optimization method yields better results under similar cases.Finally,the sensitivity analysis of dwell time increment is carried out.