1.3 Research Method

Urban planning research is not conducted as a simple linear process, but involves a variety of surveys, often feedback to each other. We try to explore various ways to study various urban and structural phenomena, as well as their design and analysis, and be open to what they might lead to. Towards the end of the study, a more integrated process emerged, in which various original research directions were eventually linked.

1.3.1 Literature

We start with different urban structures and design concepts to explore the relationship and function between traffic and urban planning.

In between the consideration of design analysis and design recommendation was the consideration of the more theoretical topics of urban structure and structuring. This entailed the consideration of a more eclectic and specialized range of subjects, including the professional and historical context of design, the geography and geometry of networks, as well as various philosophies of design and growth of form.

The following conclusions can be drawn from the analysis of the Athenian charter:

（1）Human activities are the main activities and decisive factors of urban transportation. The demand, willingness and energy of human activities determine the purpose, mode, frequency and distance of travel. The distribution and activity demand of people in urban land determine the flow and distribution of urban traffic. The study and arrangement of urban traffic in urban planning must be based on the activities of people and the distribution of people in urban land.

（2）Urban land use is the decisive factor of urban traffic. Urban transportation is generated from urban land use. A certain urban land use layout produces a certain traffic distribution, and a certain traffic distribution must be matched by a certain road and traffic system. The structure and form of urban road network and public transportation network depend on the layout structure and form of urban land, which should be coordinated with the layout form of urban land.

（3）To deal with the reasonable urban land layout and road system, to have the thought of the public traffic and function division, according to the land use of traffic of different functional requirements, reasonable arrangement of different types and functions of the road, beside the road of different function arrangement different nature of the construction land, the formation of road traffic system and city land layout reasonable cooperation relationship.

The history of urban development tells us that the unreasonable traffic distribution is caused by the unreasonable land use, the unreasonable urban layout makes the distance between work and residence too far, and the unreasonable traffic distribution is the root cause of road congestion and traffic obstruction. In the process of urban development, people have gradually realized that the city expands outward in a concentric circle around the original single center of the old city, constantly enlarging the travel distance of people and cars, and constantly increasing the traffic burden in the central area of the city. Therefore, the traffic problems generated by the city cannot be solved by road construction and traffic management alone. The organic evacuation theory proposed by reveals an effective way to alleviate urban traffic by changing the urban layout: the layout of cities in clusters and multi-centers can greatly reduce travel distance and cross-district traffic volume, make traffic balanced distribution and fundamentally solve the traffic problem.

So, study the urban traffic problem must first study the city land layout, ideas to solve the problem of urban transportation must first change, from“the”point of view, based on the rational distribution of urban land, through optimizing urban land layout optimization of traffic distribution from traffic sources, the overall should form multi -center layout depended, urban land to comprehensive layout, a group to achieve perfect basic functions;Secondly, we should deal with the relationship between urban land use layout and road system, and optimize urban traffic and road system through the functional layout of urban traffic and road system coordinated with land use layout. To have the thought of the public traffic and functions of thought in accordance with the land use of traffic of different functional requirements, reasonable arrangement of different types and functions of the road, beside the road of different function layout is not back to the nature of the construction land, the formation of road traffic system of urban land consolidation layout reasonable cooperation relationship）and to organize a group of traffic and across groups, sexual life of traffic and transportation, simplify and reduce the rate of traffic after the spear.

For cities of different sizes and different types, the basic relation of traffic distribution should be studied from the perspective of land use layout, different road traffic network types and modes should be selected according to local conditions, and different road density and traffic organization modes should be determined.

1.3.2 Description and Analysis of Structure

The urban road system is always accompanied by the development of regional cities. The development of any city goes through a process.

As cities develop into medium-level cities, large cities and megacities, the centralized layout with land use develops into a combined layout, and the form and structure of urban road transportation system should also undergo fundamental changes.

The city formed in the early stage is a small town, which is also the“old city”part of the later developing city. City is affected by the feudal rules and regulations in China, different grade“old city”of the city scale is different, but most of the present centralized layout for center, the field of city roads are mostly whole squares, despite of the primary and secondary points（still can be divided into one, branch and street level）, but significantly narrower width, density is high, more suitable for walking and non-motor vehicle traffic of the seats. The city located in the water network developed area may have the river road fusion, the irregular grid pattern or other forms, the small town located in the traffic important road location may also have the peripheral radial pattern which connects with the urban road network.

The development of a city to a medium-sized city may still be centralized, but there will inevitably be multiple sub-centers. A reasonable urban layout should gradually form a multi-center and relatively compact group layout by strengthening the construction of sub-centers, thus making the urban traffic distribution more reasonable. In the central group, the urban road network still maintains the basic pattern of the old city, while in the peripheral group, the modern three-level road network that is more suitable for motor traffic will be formed，and the grid pattern will still be maintained.

When a city develops into a large city, if it still follows the single-center centralized layout, there will be a series of common problems in big cities, such as too long travel distance, too centralized traffic, traffic congestion and low efficiency of the city. Therefore, the planning must guide the city to gradually form a relatively scattered and multi-center group layout. The central group（which can be composed of the original medium cities）is relatively compact and independent, while several peripheral groups are relatively dispersed. In addition to the third-level road of modern city, the urban express road required for the formation of modern urban traffic between the central group and the peripheral group should be considered, and the urban road system starts to transform into the mixed road network.

The layout of megacities may be“combined city”, and the outer city of city will be further developed into several relatively compact peripheral cities based on the original peripheral towns. The central city is developed, adjusted and further combined on the basis of the original big city. Urban road development creates mixed visualizations, there is a need for a reworked POE municipal road network to enhance intercity traffic connections and a sulfur connectivity arterial road network combined with a rapid road network, which can also be linked between urban areas using highways or expressways.

Generally speaking, the site layout of the old city is relatively compact, and the road network is relatively close and narrow. High density makes traffic more dispersed. Narrow capacity, then can organize one-way traffic, suitable for dispersive traffic mode. In big cities, urban peripheral more put land layout, in order to adapt to the characteristics of long travel distance, requires traffic speed, to organize efficient sets the amount of traffic flow, match with high efficient road traffic facilities, it needs to have a distinct shunt type road network structure, compared to the old city, density is lower, width is ability to adapt to modern traffic will be larger.

The above analysis shows a general rule: different scale and different types of urban land layout have different traffic distribution and traffic requirements, there will be different road network types and modes, and there will be different road network density requirements and traffic organization methods. Therefore, different cities may have different road network types; different urban areas or sections of the same city may have different road network types due to different land layouts. Different types of urban trunk road network are closely related and closely coordinated with different urban land use patterns.

The research has involved various types of description and analysis of network patterns and structures. This has included general descriptions of network shape, and more detailed geometric and morphological approaches. No single school of thought or analytic method has been adhered to. In fact, the research has precipitated the development of new methods of analysis of network structure, based on consideration of the route as the elemental unit of analysis and design.

This approach combines the strengths of a series of existing approaches, including those based on graphs of nodes and links, spatial configuration, and morphology of plots or buildings.

1.3.3 Use of Examples of Urban Structure

Examples of urban structure have been used to demonstrate different forms of network structure, and in some cases to‘calibrate'certain proposed indicators of structure with recognizable‘types'. This process has aimed for breadth, across a diversity of urban cases, comparing their similarities and differences, rather than tracing the detailed design history or particular design problems of any particular locality. In the pursuit of exploring variation（or similarity）between different urban structural contexts, several examples have been drawn from outside the UK.

The examples of urban structure include not only patterns or designs‘as built'on the ground, but patterns drawn from design guidance or design proposals. Addition, for the purposes of illustration and demonstration, Beijing, Tokyo and some other conceptual cases are cited in this paper.