| At present,the railway network planning in China still adopts traditional"railway-oriented" approaches.With the development of urban structure and transportation facilities layout current planning methods cannot meet future challenges of the railway industry.The experience of railway planning in foreign countries shows that,the "human-oriented" planning concept will be the one of the most important directions for the new railway network planning system.The "human-oriented"planning methods focus on satisfying the individual travel demands and aims to increase system-wide accessibilty.Consequently,the travel convenience of passengers and the comprehensive level of service in railway systems can be significantly improved.The individual accessibility under time constraints(that is,time-space accessibility)is introduced into the regional intercity railway network planning problem.To address the proposed problem a linear programming model and a Lagrangian relaxation-based algorithm are developed.This study provides a reference for the accessibility-oriented problem in railway network planning.The main work and innovation points of this paper are listed as follows.(1)The basic theoretical knowledge of intercity railway network planning is systematically analyzed.Firstly,the definition of intercity railway and the relationship between intercity railway and other transportations modes are described.Secondly,the service scope and function orientation of intercity railway is discussed.Thirdly,this paper analized the technical and economic characteristics of intercity railway,passenger demand characteristics and operating characteristics.Finally,the definition of intercity railway accessibility and time-space accessibility are provided.(2)A regional intercity railway network planning model is constructed in order to maximize time-space accessibility.Firstly,the minimum number of inaccessible OD pairs of intercity railway network is considered as the optimization goal.Secondly,this paper considers passenger travel time constraints,intercity railway construction constraints and intercity railway construction cost constraints.Thirdly,a linear programming model of intercity railway network planning based on time-space accessibility is established.Finally,a small scale example is used to verify the correctness of the model(CPLEX).(3)The solution algorithm of regional intercity railway network planning model based on time-space accessibility is designed.Firstly,travel time constraints and intercity railway construction constraints are relaxed into the objective function.Secondly,the relaxation problem is decomposed into three classical problems which are minimum cost path subproblem,knapsack subproblem and unconstrained 0-1 management planning subproblem.The Lagrange multipliers are updated through the gradient method to find the lower bound of the primal problem.Thirdly,a feasible solution of relaxation is generated,so as to obtain the upper bound of the primal problem.Then,the solution quality is demonstated.Finally,a small example is given to verify the correctness and efficiency of the algorithm.(4)A case study of Beijing-Tianjin-Hebei region is conducted.Firstly,the Beijing-Tianjin-Hebei region intercity railway planning network in 2020 is simplified.Secondly,the K-Means clustering method is used to divide the 28 main cities of the simplified network into 5 categories.Thirdly,after calculating the number of inaccessible OD pairs of the simplified network is 34.Finally,new intercity railway lines in Beijing-Tianjin-Hebei region are desiged.The results show that,when the budget is 136 billion 940 million yuan,9 intercity railways(783.3 km)in Beijing-Tianjin-Hebei region are constructed.The construction will not only improve the individual accessibility of the intercity railway network,but also reduce the number of inaccessible OD pairs to 12.The total number of inaccessible OD pairs reduces by 22 and decreased by 64.7%compared with the original plan. |
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