Research On Time-transfer Accessibility Model Of Multilevel Urban Rail Transit Network

The concept of development for urban rail transit has changed in our country,developing urban railway transit at different levels will become a trend.Accessibility is a quantitative index for evaluating the quality of network.At present,the research on the accessibility of urban rail transit network is mainly measured by the topological distance characterized by transfer times.This method is quite reasonable for rail transit network in central.However,the study on accessibility of multilevel urban rail transit network only considers that the transfer times can not reflect the difference of network level.More attention is paid to travel time of rail transit in municipal.Therefore,this paper puts forward a new method to study the accessibility of multilevel urban rail transit network with time and transfer factors,which play a positive role in enhancing the ratinality of network planning.Combining with the speed and transfer characteristics of multilevel urban rail transit network,this paper explores methods to calculate accessibility of multilevel urban rail transit network.The main research contents of this paper include:(1)The time accessibility model based on GIS and topology accessibility model based on Space P model are studied and established.On the one hand,the digital urban rail transit network is built with ArcGIS,and the network analysis model is used to calculate the time accessibility of the multilevel rail traffic network.On the other hand,according to the transfer relationship between stations in rail transit network,the adjacency matrix of Space P model is constructed,then the topological accessibility of the network is calculated by Floyd algorithm.(2)Combined with time and topological factors,the time-transfer accessibility model is built.The calculation idea of taking the bi-objective shortest path as the centre is determined.Time distance matrix and adjacency matrix of Space P model for urban rail network are built.Since the bi-objective shortest path based on complex network is difficult to be solved,a reasonable restrictive conditions are proposed,and twice depth first search algorithms are designed,and the time-transfer accessibility of network are calculated.(3)Taking Beijing urban rail transit planning network as an example,the time accessibility,topological accessibility and time-transfer accessibility of network are calculated respectively,and the rationality of the three accessibility models is verified with the passenger flow data.The results show that the time-transfer accessibility combines the features of time and topological accessibility,and the correlation coefficient with passenger flow is much higher than the single time or topological accessibility,which shows the advantage of the time-transfer accessibility model.(4)The model of grade division of rail lines based on the grey theory,whitenfunction are built respectively,Grade of rail lines based on the accessibility and the multi indexes of rail lines are divided.The results show that,grade division of rail lines based on time-transfer accessibility is reasonable.In the early stage of rail network planning,grade division of rail lines based on accessibility has guiding significance for selection of technical indexes of rail lines.(5)The effect of different line types on the accessibility of network is studied.The results show that the radial line has improved the time-transfer accessibility of network.The influence of radius line on the accessibility of the network is related to the number of lines which connected.That radius line connects more other lines can enhance the accessibility of the network.In the radial line,the promotion effect of express lines on time accessibility is higher than that of topological accessibility,but for the normal speed lines,it is opposite.(6)Due to the complexity of network problems,the rules of distribution for time-transfer accessibility is difficult to grasp.Therefore,this paper studies the distribution of network accessibility based on fractal theory.Within the circle area of radius 10km,the accessibility distribution of the network is uniform,the attenuation rate is slow,and the rail transit have highly supply capacity.For the 10-30km annular range,the decay rate of accessibility is fast,the accessibility distribution is uneven,and the rail transit capacity is lacking.Rail service lines in the range of 30-50km are the least serviced.In the future,it is necessary to build express lines with high speed to strengthen the connection with the urban centre.The building and application of accessibility model on multilevel urban rail transit network provide a theoretical basis for rational planning of urban rail transit network,and it can be applied to the actual planning projects and provides assistant planning decision.