Study On Transit Route Network Optimization Design

Public transit network design is the key part of the development of the public transportation planning. The design of urban public transit network has a decisive influence for residents’ daily life, working trip and even the healthy development of urban economy and society.Transit route network design is mainly consist of two parts, which is the design of bus route and calculating the frequency. To balancing benefit of users and operators, two ideas are used to solve the design of bus route network problem(TRNDP), which are layered planning and overall planning. The integer programming models are formulated, which are objective to the minimization of the total system cost and subjecting to the limitation of length, the minimization frequency, the capacity of bus and so on. The total system cost is the summation of the passengers cost and operating cost. The study is based on traffic zones, which assumes that each have multiple site. And the shortest path algorithm is applied for the set of initial candidate lines. Then the difference between two modeling framework appears. The overall planning modeling approach based on the Nested Logit model and the combination of multi-mode split. According to the method, route selection and demand assignment can be determined. The best bus network structure and frequencies is determined by the method of combination and adjustment. The layered planning use K shortest path method to expand the initial candidate lines, and the alternative network structure and frequencies is determined. According to the level division, we can realize route selection and demand assignment, and calculate the total cost of system and achieve the best solution. Both of them use SA algorithm to solve the TRNDP model.In the past, researchers assumed that each only have one site, which is different from the actual situation, and could cause greater error. And the problem of travel mode single and ignoring the mode choice always could be found. Unlike previous studies, the overall planning thought is put forward, which considers the mode split and transfer. The results shows that the overall planning can be used for large-scale network, and provide good auxiliary decision-marking.Two decades ago, the concept of layered planning has been presented in China. But the proposed model cannot determine bus network structure and frequencies at the same time. In this paper, the layered planning method can solve the problem. Numerical example results show that the layered planning is effective auxiliary decision-making tool in the design of large-scale transit network.The model presented in this text and the corresponding calculation results are more stable, and can be used in actual large-scale network. And the proposed methods in the study provides a new thought for our country large-scale transit network design.