Optimal Design Method For Intercity Demand Responsive Transit Service

Intercity Demand Responsive Transit(IDRT)is a kind of “door-to-door” intercity transportation services that can directly transfer passengers from a departure point in one city to a destination in another city.Although IDRT service has been applied in some cities in China,there is limited research to guide the optimal design of the service.Therefore,this paper proposes an optimal design method for IDRT service based on the relevant research work at home and abroad.Firstly,this paper proposes three service modes: No Partition mode,Partition mode,and Partition & Transfer mode based on IDRT service scenarios.Then,the paper describes the operating policy of “no backtracking strategy” and the dispatching process.Secondly,this paper formulates optimization models for the three IDRT service modes.The decision variables include the area of the main city zones,the number of subzones and the headway of fleet.The optimization objective is to minimize the average total system cost which consists of operating cost,waiting cost,in-vehicle cost,and transfer cost.Besides,a coordinated transfer strategy is introduced in the Partition & Transfer mode to reduce transfer costs.Thirdly,to facilitate solving the models,the proposed optimal problems are divided into local problems,partition problems and transfer problems.The penalty function method,downhill simplex method,greedy algorithm,and pattern search method are used to solve these three subproblems one by one.The results obtained under the basic scenario show that the objective function of the Partition& Transfer mode is reduced by 13.54% compared with the No Partition mode,and is 4.31%lower than the Partition mode.Furthermore,the correctness of the models and the solutions are verified by simulation of the operation process of IDRT.Finally,this paper presents sensitivity analysis of some key input parameters(i.e.,passenger travel density,intercity transportation distance,service area,vehicle capacity,and cost coefficients),which can provide decision-makers useful suggestions to design the optimal IDRT services.