Research On Network Design And Optimization Method Of Urban Public Transportation

With the fast development of China's economy, as well as the rapid progress of urbanization, the number of vehicle owners is increasing rapidly. One consequence of this fact is the serious urban traffic congestion, which greatly affects the daily life of urban residents, hinders social and economic development, and increasingly deteriorates urban ecological environment. Compared with individual traffic, public transportation is advantageous in terms of resource consumption, environmental protection, transportation efficiency, and transportation costs. These advantages make problems regarding public transportation development the primary concern in urban traffic system. So far, such problems are still very conspicuous, including lack of unified planning in infrastructure of most urban public transportation facilities; poor quality of transit service, causing a low share rate of bus transit; general deficit of public transportation enterprises and lack of scientific and reasonable financial compensation mechanism. To this end, it is hoped that formulation of a scientific and rational planning of public transportation will guide the sustainable development of the system. As the core of such planning, the reasonableness of urban public transportation network design and optimization will directly influence the operability and rationality of such planning.Researches at home and abroad on network design and optimization of urban public transportation have provided a lot of valuable experience,but there are still some disadvantages: Network design of urban transit is often optimized for a single target,without taking into account other optimization goals; In particular, it is difficult to meet the requirements of line overlap factor and network coverage. Even taking into account the multiple objectives, with each objective function weighted, the final weighing still needs further research. A majority of methods need enormous calculation. For example, there are too many variables to be solved in the application of heuristic algorithm on network design; Besides, repeated trial calculations of network parameters are involved to achieve global optimum. In spite of the convenience for computation of heuristic algorithm, for large-scale network design, human intervention is still preferred to reduce the model calculation. A majority of methods need a combination of qualitative analysis and empirical judgments,can not achieve one-time automatic network design by computer; The methods of passenger flow assignment used before are not fully in line with Chinese commuters'habits; and can not reach a satisfactory assignment result when applied to China's passenger flow assignment.This paper,which aims to avoid the disadvantages of the key models and algorithms in transit network design and optimization,has the following research findings: Improving the traditional investigation methods on transportation and the previous passenger flow forecasting methods, with regards to the actual situation in China; researching a multi-objective public transportation network design against disadvantages including excessive calculation during transit path search and experience-required judgment in the design process; establishing a transit network assignment model based on analysis of the characteristics of Chinese commuters and researches on their commute strategy; improving the public transportation network evaluation system; proposing a TransCAD-based optimization method of public transportation network directed against the disadvantages in existing public transportation system.The main findings are as follows:First, according to data surveyed in Changchun, the bus arrival time is proved to be generally normal-distributed. Based on the fact that data is incomplete in IC card database, a new method is proposed---the OD of the bus passenger---based on IC Card data flow. Because the management measures of the urban cars greatly affect the passenger share of the public traffic, the car capacity forecast based on environmental constraints is proposed. When management measures of urban cars are got, the total public transport trips is predicted by using data provided by improved OD survey and Markov chain methods. Because of the past insufficient method to demarcate gravity model by using the space between the line centroid distance or the shortest distance between the centroid (or time) as the traffic impedance plot between the areas, we propose a traffic impedance determination method based on the internal road node. Through analysis of bus needs change based on different bus supply strategies, we conclude that regional transportation needs is consistent with population change.Second, against the disadvantages of the past searching method of transit path which needed enormous calculations and because the design process required empirical judgments, the author proposed the direct cross-network design based on mechanical analysis of the transit path search algorithm, and on the basis of the direct transit network, rout connection design algorithms was proposed based on a reasonable path alternative.Third, commuting strategies are brought forward on analysis of the features of Chinese commuters and according to the strategy the public transport route choice model which is station-based is established. The method of passenger flow assignment used before assumed that all passengers were able to be assignted into the traffic network, without considering the fact that some passengers gave up public transit because of long waiting time and over crowded buses. Based on this problem, a new concept---passenger expectation failed---is put forward, describing the effects of public transit service on commuters. According to the passenger's behavior for the start bus stop, after analysing advantages and disadvantages of bus route choice model based on the ML model and choice model based on NL model, the paper introduces choice model based on collinear transit path and passenger loading algorithms.Fourth, using non-linear factor to justify bus lines is one-sided, thus the author first proposed using the consistency of bus lines and passenger flow to describe whether the bus lines are in consistency with the passenger flow. The rationality of public transport network is then explored from the network communication, reaching two-pronged approach to explore, and a rationality evaluation index of the public transport network's accessibility are proposed based on the data surveyed.Finally, corresponding measures are proposed based on the deficiencies of passenger flow distribution models in TransCAD. TransCAD assignment model (AON) is used to allocate passenger flow on the public transit network to get the selection of minimum cost commute on the condition that all the passengers do not care about the crowded buses. Compared to this commute, unreasonable lines in the network are determined. A concept—line substitute degree—is proposed to describe the extent of the lines being replaced and to provide the basis for line removal because of excessive number of lines. For the connection of additional bus stations in blind sites, the concept of expanded bus stations is proposed to design the connecting of bus routs. By using the minimum total commute as the evaluation index, the optimization program is evaluated and the optimizing process by using TransCAD is briefly introduced.This research will enrich the theory of system planning of urban public transport and improve methodology, which will provide scientific decision-making analysis for the implementation of special public transportation planning and traffic management.