Conventional Bus Route Network Optimization And Application Under The Impact Of Urban Rail Transit

With Chinese urbanization developing rapidly, the contradiction between demand of urban transportation and supply of transportation infrastructure has become increasingly prominent problem. The problem of urban traffic congestion not only affects people’s normal life, but also seriously hampers the economic development of a city. Therefor, under the process of urbanization, to solve the contradiction between demand and supply of urban transportation is very urgent. At the same time, as one of tool of solving the problem of traffic congestion, urban rail transit has been widely promoted in China’s major cities. However, the density and coverage of urban rail transit network are limited. In order to let urban rail transit to play a major role in urban transportation by its large capacity, high efficiency and other advantages, it is necessary to cooperate with other transits. In China urban transportation system, the conventional bus had been developed firstly, and secondly it is the urban rail transit. In order to let both conventional bus and urban rail transit to constitute diversified and integrated urban transportation system, it is necessary for optimizing the conventional bus networkt.In order to study how to optimize the conventional bus lines under the effect of urban rail transit, According to the background of Chengdu public transit network system, this paper focuses on optimization of connecting urban rail transit network, and mainly do the research in following four aspects.Firstly, in order to analyze how conventional bus passengers have been affected by choosing urban rail transit as their travel tools, and based on the program object of minimum travel time for travel tools choice, this paper uses Dijkstra’s algorithm to find the shortest path of travel time, and uses MATLAB software to deusign the algorithm of bus transit Origin-Destination matrix under the affect of rban rail transit. It can provide the basic data for bus transit optimization under the affect of urban rail transit, and compared with the traditional gravity model, this method can avoid the complicated process of estimating the impedance coefficient.Secondly, based on two disaggregate models such as Logit model and Probit model, this paper has built a combined model of measuring probability of choosing transportation tool. We can estimate the probability of choosing transportation tool after the urban rail transit appears by this model, and it can compute the bus passenger allocation on transportation network. A numerical calculation show that the combination forecasting method can compensate the deficiencies of simply using Logit or Probit model.Thirdly, based on the object of minimum total travel time, this paper studies how to optimize the number of conventional bus stations paralleled with the urban rail transit lines. Under the assumption of uniform distribution of people nearby the urban rail lines or bus lines, we get the formula of optimal number of bus stations. Conclusion showed that there is a positive relationship between the number of bus stations and the bus speed. Meanwhile, that the conventional conventional bus stations and urban rail stations set up in the same location may not be the best choice. So it is necessary for re-optimizing the allocation of conventional bus stations in order to let urban rail transit along with conventional bus transit to reach maximum efficiency and to meet the needs of different travelers.Fourthly,Based on the analysis of passenger flow of the different areas and the multi-objective such as the minimum average travel time of passengers and the minimum operating costs of company, this paper establish the optimization model of the bus lines for connecting rail transit lines. We have analyzed the optimization problem such as density of conventional bus lines perpendicular to the urban rail transit lins as well as parallel to urban rail transit lins, and we design a corresponding multi-objective genetic algorithm to solve the problem. Finally we use the corresponding algorithm to analyse the bus transportation lines optimization after Chengdu Metro line 1 and line 2 have appeared.All in all, this paper have studied how to estimate the urban public transport passenger OD matrix when the urban rail transit appears, and we put forward the network optimization model for both the single conventional bus line and multi-line of conventional bus. The conclusion has some positive guiding value for the establishment of efficient comprehensive public transportation system.