Traffic Network And Its Effect On Urban Spatial Structure In Kaifeng City

Urban traffic network is an open and complex network based on urban space,which is one of the most important manifestations of human economic and social activities on the land surface.For the traffic network modeling,it is often considered through several aspects,such as the characteristics of topological correlation,traffic flow,accessibility and direction.With the development of the city,the transportation network continues to extend and be coupled with the urban spatial structure.On this basis,the logic of this study is that the transportation network is regarded as a kind of "transmission matrix" placed in urban space,as a result,the “urban homogeneous plane” is deformed under the effect of space-time compression ideally.It will form a “centrality” and “accessibility” non-uniform distribution of composite space,and two types of elements such as traffic and built up area are intertwined in this composite space.Then,the traffic contributes the base frame of the composite space,and the built-up land parcels are embedded into the traffic frame.All of the two types of elements exhibit composite structural features together.Other related further researches like urban spatial structure measurement of “Traffic-Land Integrations”,mechanism discussion,simulation optimization will be discussed based on above studies.It is of great significance that start the research on urban spatial structure of “Traffic-Land Integration” and make downtown area of Kaifeng as a case area.Kaifeng is a famous historical and cultural city of our country.It was known as the “ancient capitals of the eight dynasties”,and it has a long history and a rich heritage.The spatial place of the central axis in the historical urban area never changed during its 4,000 years building history.In the past fifteen years,the urban framework has been stretched to form two parts—a new urban district and an old one—with the city expanding rapidly to the west.The two areas have comparable size,and there are some significant differences in traffic organization and structural characteristics.For examples,in the old urban area,the road network is built on the scale of pedestrians,and the characteristics of self-organization evolution are obvious.Taking the preserved city walls,gates,motes,central axis and ancient houses as the structural basis,the spatial structure presents historical inheritance.In the new urban area,the road network is built on scale of vehicles,the spatial structure planning features are significant.It combines the modern architectural and “new song style” together as the main point,and put the regular checkerboard network as the structure base at the same time.Although the two areas are separated by the West Lake,it forms a structure “community” by interconnecting and synergistically evolving other urban trunk roads together like Tokyo Bridge,Yuxing Avenue(in planning),Zhengkai Avenue,Jian Road(in planning),Songcheng R oad,Weidu Road.It has a great value to do the research in Kaifeng area.This article takes the downtown area of Kaifeng as a case area.The frame work of “Urban Transportation-Urban Spatial Structure” is constructed.Then,the following four levels of structural research have been carried out on two types of elements such as traffic and land(built lot):Level 1: Interpretation of the frame syntax of the traffic elements themselves;Level 2: The structural measurement of build up area in the road network;Level 3: The spatial correlation and driving mechanism of traffic on land elements,named the integrated study of transportation and land structure;Level 4: Simulation and optimization of the expansion of built up area based on traffic network and traffic flow.It comes up the main conclusions as follows:1.The transportation network skeleton of Kaifeng evolved from a single center to a multi-center structure.The number of local city centers identified by spatial syntactic line segment angle model,and it increased from one in 2002(historical area evolution center A)to three in 2017(historical area evolution center A,new and old area connection center B and Bianxi area cluster center C).Also,center A is located at the intersection of East Street and Jiefang Road;center B is at the intersection of Daliang Road and Huanghe Street,and center C is located at the intersection of Zhengkai Avenue and Wujie Street.These three integration centers are in the same east-west city development axis,and they outlines the shift trajectory of the urban development from east to west.2.The construction land of new and old area forms circle structure with different characteristics,which is developed by adhesive into pieces.According to the improved reachability-based fractal measurement algorithm developed in this paper,the fractal features of “ traffic land integration” in each local center and the corresponding circle structure information are extracted.The circle structure of the historical urban area centered on A is relatively stable and structured.The structures are density constant zone,the density slowdown zone and the density dip zone from the inside to outside.The C-centered Bianxi area developed from two layers in 2012 into three layers in 2017.It reveals the development process agglomeration filling in new area from the inward and because of the corresponding aggregate dimension is definitely reduced.The junction circle structure of new old area centered on B is affected by A and C.Also,The corresponding space range is small and built density is high.In general,the core layers of three local centers are mutually fused together and gradually connected into pieces.3.The effect of traffic flow on the urban expansion in microscale has the similar nature with that in macroscale.However,the macroscopical law is more obvious.Grain size effect shows: 500 m times 500 m grid < 1000 m times 1000 m grid < 2000 m times 2000 m grid.As a result,the correlation coefficient of measured degree is low because of fine grid division will break the integrity of the original parcel in microscopic scale,and it covered up part of the traffic land related information.4.The driving force of throuth-movement on urban expansion tends to be weakened,while that of to-movement tends to be strengthened.The time span is divided into three periods: the first period(early stage of new area expansion from 2002 to 2007),the second period(formation period of new district road network frame from 2007 to 2012)and the third period(filled development period of built-up area from 2012 to 2017).Moreover,the correlation is enhanced from the first to the second time period and the correlation is weakened from the second to the third time period.From the first to the second period has a appreciably weakened and there is no change from the second to the third period in partial transit traffic flow.Also,there is a continue rising in three periods for global arrival traffic flow.For locally arriving traffic flow,different characteristics are displayed in different grids,which is more complicated.5.The main traffic drive of unban expansion swifts from local to global.In the first period: local integration degree > local integration degree > global choice degree(global integration degree),and the main traffic driving force is the mixed traffic flow of local choice and local movement.In the second time period: global choice degree(local choice or local integration)> global integration degree,and the main driving force for urban expansion is mixed by global and local choice and local choice to-movement.In the third period: global integration degree > local choice degree(local integration degree)> global choice degree,and the main traffic driving force of urban expansion is global to-movement.Combined all the period together in the end(2002-2007): local choice(local integration)> global integration(global choice),and there is a much stronger operation in various types of traffic on urban expansion than other period segments.6.A variety of urban expansion modes coexist.Under different scenarios,urban expansion shows different combinatorial models,among which the new central growth model is always one of the dominant modes.The scenarios are as follows:(1)Superimposed global choice movement: urban expansion presents a mixed patter of new central,slight and road gravity types.(2)Superimposed local choice movement: urban expansion presents a pattern of mixed growth in self-style,edge-type and road gravity type.(3)Superimposed global(or local)to movement guidance,the urban expansion is dominated by new central,self-development,and it presents a pattern of mixed growth in edge type and road gravity type.7.By loosely coupling the spatial syntax model and the SLEUTH model,it can effectively improve the simulation accuracy on the pixel scale and enhance the interpretation of urban expansion.Also,it can capture the transfer of urban development centers due to policy factors such as urban planning and find out the new central growth area(Bianxi District).It means,there is more further research positions in the topology analysis method for integrating spatial syntax “top down” and cellular automaton “bottom up” neighborhood conversion rule,which can provide a reference for cities with dual-core(old and new districts)linkage type.8.According to the simulation results,The future development of Kaifeng urban space includes four key areas,and the corresponding construction directions are as follows:(1)The northwest region centered on Daxinzhuang and Xiaoxinzhuang: it is crucial to strengthen the vitality of the city as the main construction goal,in addition,creating a gateway to the northwest of Kaifeng City is necessary.(2)The west region along the Zhengkai Avenue,which has a span from the 6th street to 10 th street,is the center of the western part.It is important to focus on improving the quality of this area,and the main goal is cultivating the development momentum of urban agglomeration and put more attention in high-end positioning.(3)The southwest region centered Apricot Flower Town: this area should be planned ahead of time.In addition,the way of unban expansion will be extension type,docking well with downtown in the aspects of industry,ecology and transportation is essential.(4)The east region centered Lichang Village: The optimization measures should be based on regulation and controlment.Attention must be paid to the small and refined development,not to “an over-spilt mode”.The innovations of this paper are as follows:(1)Having achieved fractal study in urban spatial structure of transportation-land integration,it constructs a gathering dimension based on traffic accessibility.(2)Having conducted a structure study of holistic and comprehensive,it establishes an urban spatial structure analysis framework under the perspective of traffic.Also,it integrates static traffic “network” and dynamic traffic “flow” into the research system.(3)Having integrated the “top-down” road network topology and the “bottom-up” CA simulation idea,it refined simulation of urban spatial structure based on high-resolution images.