Research On The Optimization Method Of Urban Public Transit Line Network In The Near Future

One of the fundamental contents of public transport priority is to optimize the bus network; it is the basis for developing urban public transportation system service level and competition. The short-term optimization of the public Transit line network has its specificity that is diferent from the long-term plan and the optimization of the current public transit line network, and whose research objects are concered with both the network structure optimization at the macroscopical level and the individual bus line adjustment at the microcosmic level.This paper divided bus network optimization into three parts to discuss: evaluation of the public transit line network; public traffic demand forecast; short-term optimization models of the public transit line network. The analysis and evaluation of bus network is the precondition of bus network optimization. Only do the right and science evaluation, we can find the problem in bus network and provide the reason gist for bus network optimization. The public traffic demand forecast is the foundation of the bus network optimization; it can provide base date for bus network optimization. Through the public traffic demand forecast, we can analyze problem in current bus network and evaluate planning bus network in the near further. The method of the short-term optimization of public transit line network is the point of bus network optimization. According to the different object, different restriction condition, different method of the solving, the form of the bus neworkt is different. So we must be careful choice the optimization object, the restriction condition and adopt the right method of solving.This research consists of five chapters. The main works and contributions are described as follows: 1. Evaluation of the public Transit Line networkEvaluation of bus network is the foundation and precondition to public transit line network optimization. Analysis of current bus net includes selecting the evaluation index; establishing the evaluation index system and choosing the evaluation method. Evaluation of the public transit line network in this paper has three layers: public transit line network; public transit line; public transit station. The second chapter gives the definitude definition and calculating method of each index. Based on the past study, considering the development trend of current bus network, some indexes have been corrected that will be more reasonable and efficient reflection the service level of the public transit line network. By using the fuzzy mathematical principles, a synthesis evaluation method for the public transit line network was set up. It was finally applied to the practical evaluation of public transit line network in Changchun city, and the results were obtained satisfactory.2. Forecasting of the public traffic demand.The past public traffic demand is base on the classic"Four-stage"traffic demand forecast, using traffic model split calculates the proportion of public traffic demand. Public traffic demand forecast in this paper based on the improvement Four-stage frame, studyed public traffic split model. The public traffic split in Traditional Four-stage Process frame is the third step, that didn't consider the different in each traffic zones. The public traffic split in this article is after the trip production forecast, public traffic demand forecast will be calculated by whole traffic mode demanding multiply the public traffic split rate. The public traffic demand will be distribution by the condition of land use in each zone. Then the public traffic generation and attraction will be revised by the value of trip generation and trip attraction multiplie the public traffic split model. In the process of calculation public traffic split rate, the paper firstly split travel mode to the no-competition mode and competition relation mode, the on-competition travel mode adopt the fix proportion rate and the competition travel mode adopt the improvement disaggregating model to forecast the public traffic demand. Based on the competition between bus and other traffic mode, article adjusts the split rate between different competition traffic modes by devising the general travel impedance model. Finally we validate the public traffic demand forecast model based on the date in Changchun city; the result indicates that method has nice split precision.3. Research on the optimization method of public transit line network in the short-termThe optimization method of the public transit line network in the short-term is the core and the point content in this artical. The design of the public transit line network is the most important plan step in the optimization progress. The design bus network not only impacted establishing of the bus interval, but also impacted distribution of bus conductor. If public transit line network is done, the bus company didn't change it frequency. Especially before the implement of intelligen public transit system, if the design of public transit line network didn't reason, that would impact the whole effect of intelligent public transit system.Based on the considering that public transit line network should have the dividing of the function as urban road network, article proposes the optimization method of public transit line network is"multi-layer restriction, step by step condition". The method has divided the public transit line into three layers that is: major public transit line; minor public transit line and the collector public transit line. Regard as the different grade line, designing the different objects. The optimization object of major public transit line is the maximum direct passenger flow volume; the optimization object of minor public transit line is the lowest rate of average transfer times, the optimization object of collector public transit line is the lowest of general travel cost. In order to improve the speed of search, increase the efficient, restricting search space of result in the process of solving, the search space of different object is restrict in efficiency path of the correspond public transit line layer. However, with a practical size problem, the conventional techniques are facing the challenge to effectively and efficiently solve those complicated network design problem(NDP). In this article, we propose a new optimization model; develop an improvement genetic algorithm to solve the model. The algorithm has two features: priority-based encoding method and multi-layer search space. The author has given a definitude demonstration and the particular solving step.In the method of public transit line adjustment, article proposed the step by step heuristic adjustment method based on the actuality stage public transit line network. Because the actuality stage of public transit line network was worked up, that accords the trip habit. So the near future optimization doesn't change it a lot. The public transit line network which calculates from the genetic algorithm will combine the actuality stage public transit line network, adopted the step by step heuristic adjustment method adjust the public transit line network. The ideas of that method is designed start and terminal station content the start and terminal station in the actuality stage public transit line network. So we will accept or reject some line, the criterion of accepting or rejecting is compared efficiency of public transit line in the plan year. In the last we give result of public transit line network in the traffic simulation base on the optimization method of the multi-layer restriction, step by step condition, and adjust the public transit line network adopt the step by step heuristic adjustment method combine the actually stage of public transit line network. The evaluation result shows that the public transit line network which optimized more according with the trip demand.4 Concluding remarks of the research.The main research achievements and further study problems are pointed out.