Optimization For The Diametrical Bus Lines Considering The Urban Rail Transit Network

Developing the public transportation is the key to overcome urban traffic congestion problems.With the advent of the age when urban rail transit dominates the public transport network in big cities,the function orientation of the bus transit has changed,and the bus network needs to be optimized and adjusted urgently.Thus,optimizing the existing diametrical bus lines considering the urban rail transit network will not only help to better coordinate and cooperate between the two modes but also improve the competitiveness of public transit network.Based on the in-depth analysis of the existing research results,the factors affecting the schemes of the diametrical bus line are summarized and the relationship among the factors is analyzed.Then a passenger choice probability model based on Logit-SUE is established to analyze the impacts of passenger travel demand and urban rail transit network on the passenger choice probability of the diametrical bus line located in the urban rail transit network.In view of the unbalanced spatial distribution of passenger travel demand,the optimization methods of bus line limited-stop scheme and bus line splitting scheme considering the urban rail transit network are proposed respectively.The main contents and conclusions of the dissertation are shown as follows:(1)Influencing factors of passenger travel demand,bus system service level and bus company costs on the schemes of the diametrical bus lines are summarized based on related literatures and the relationship among the factors are analyzed.The results indicate that the bus company costs are related to the passenger travel demand through the bus system service level.Balancing the passenger travel costs and the bus company costs and minimizing the comprehensive objective of passenger travel costs and the bus company costs are the basic objective of the bus line optimization.In the process of bus line optimization,firstly,the impacts of congestion degree in bus vehicles on passengers’perception of travel cost should be considered.Secondly,the reliability of bus lines is mainly related to the road conditions,the number of stations the bus vehicle stops and the number of passengers getting on and off each bus stop.Thirdly,the impacts of unbalanced section load factors of bus lines should be taken into account in bus line optimization in order to improve the equilibrium degree of the section load factors as much as possible.(2)Based on the public transit network consists of the urban rail transit and bus transit,a passenger choice probability model based on Logit-SUE is established.Then the influence of passenger trip distance distribution,passenger time value,passenger’s perception coefficient of travel cost,the scale of urban rail transit network and the headway of urban rail lines on the passenger choice probability of the diametrical bus line located in the urban rail transit network are analyzed.The results indicate that,in terms of passenger travel demand,the passenger choice probabilities of the diametrical bus line are different under different passenger trip distance distributions,and the trend doesn’t change that the larger the passenger average trip distance is,the smaller the passenger choice probability of the bus line is,under whatever distribution.The bigger the passenger time value,the smaller the probability of choosing the bus line,and the more prominent the advantages of urban rail transit.Meanwhile,the bigger the passenger’s perception coefficient of trip cost is,the smaller the randomness of passenger flow assignment result is,and the bigger the passenger choice probabilities of paths with smaller travel costs are.As for the impacts of urban rail transit,the larger scale of urban rail transit network,the smaller passenger choice probability of the diametrical bus line,and the greater the influence of the headway of urban rail lines on the passenger choice probability.(3)Aiming at the unbalanced spatial distribution of passenger travel demand,the optimization model to determine the bus vehicle stop decisions along the bus line stations considering the influence of urban rail transit network is established.The objective of the model is to minimize the passenger travel costs and the bus company costs.In the description of the bus company costs,the influence of the imbalance degree of section load factors of the bus line is considered.The decision variables of the model are the bus vehicle stop decisions at each bus station and the headway of the bus line.A solution algorithm is designed and the feasibility and validity of the model and algorithm are verified by a numerical example.At the same time,the optimal scheme combining two bus service patterns is put forward,in which the all-stop bus line is added,and the influence of the normalized passenger flow limiting measures for the urban rail stations on the optimal schemes is analyzed.The research shows that,firstly,considering the impacts of urban rail transit network,optimizing the scheme of the bus vehicle stop decisions along the diametrical bus line stations can help to reduce the comprehensive target value which reflects the passenger travel costs and the bus company costs.Numerical results show that the comprehensive objective value is optimized by about 11.0%.Secondly,optimizing the bus line limited-stop scheme has better effect on reducing the operation cost of the bus company,while the optimal scheme combining two bus service patterns has better effect on reducing the passenger travel costs.Thirdly,when urban rail stations adopt normalized passenger flow-limiting measures,the urban rail lines are very congested.Then optimizing the bus line limited-stop scheme has limited effect on reducing the comprehensive target value,and more bus stations the bus vehicle may stop compared to the situation when no passenger flow-limiting measures are taken.(4)Aiming at the unbalanced spatial distribution of passenger travel demand,the optimization model of the diametrical bus line splitting scheme considering the influence of urban rail transit network is established.The objective of the model is to minimize the passenger travel costs and the bus company costs.The decision variables of the model are the origin and terminal bus stops of the sub-lines,the bus vehicle stop decisions at each bus station along the sub-lines and the headways of the sub-lines.The validity of the model and algorithm are verified by a numerical example.Then the effects of different optimal schemes are analyzed.The research shows that,under the condition of unbalanced distribution of passenger travel demand,the optimal bus line splitting scheme considering the influence of urban rail transit network can better reduce the comprehensive target value and further improve the average value and the equilibrium degree of the load factors of bus line sections.Numerical results show that the comprehensive objective value is optimized by about 27.2%.In terms of the load factors of bus line sections,the numbers of sections with load factor higher than 80%and lower than 30%decrease by 2 and 5 respectively.The proportion of sections with load factor within a comfortable range to the total number increased from 58.1%to 80.6%.