1.2 Scope

In the introduction part of the paper, a series of extensive problems are proposed, and the background is set for the research topic, from which a more detailed set of goals is determined. This section provides an overview of the scope of a range of related theories and more precisely frames the subject areas covered in this article.

1.2.1 General

The urban design debate is an integral part of the norm, and the urban structure idea it proposes should first be considered as a desirable position. The position of this paper is based on the expectations and goals of contemporary theory and practice. These aspirations are seen as embodying the broader social, cultural and economic contemporary wisdom of urban life and are seen as sustainable. Therefore, this paper does not recommend what is a good or bad urban structure, but aims to help better understand the urban structure, thus providing a design method that can be customized for various potential desirable urban structure results.

We focus on the design concept. From the research limitation of the design principle and method, the specific design idea or design specification without the solution is revised. Therefore, by adjusting the research basis, this paper makes corresponding suggestions for the subsequent theoretical research methods and existing design management, thus proving its practicability in principle.

1.2.2 Scope of Urban Structure

Urban structure refers to the physical and spatial structure of urban and regional architecture. In essence, the urban structure is regarded as the continuous structure of urban road and flat space as the medium of public accessibility. This is reflected in various aspects in the structure of public space, street pattern and the ultimate traffic network. In the discussion, we will further emphasize the differences between different transport network structures and mobile space. Urban structures are seen as distinct from urban forms and urban structures, which are thought to deal more with three-dimensional forms and their surfaces.

In this paper, we do not pay attention to the conceptual interpretation of urban structure, such as social structure, economic structure, administrative or institutional structure, will not be included in the scope of this study. Of course, this is not to say that these structures are important or to deny their possible relationship to physical structures. However, conceptualized urban structure may be conceptually excluded from the physical aspect of the structure, which is the subject of this study, which we have clearly defined.

1.2.3 Scope and Interplay of Policy Spheres

The goals of urban planning and design will include a desire for sustainable cities, urban quality and vitality. The broad goals of transport planning will include integrated transport, which aims to improve efficiency and sustainable mobility. To some extent, there is consensus and reinforcement. Sustainable mobility and sustainable urbanization can support each other. But there are also conflicts in some areas, which are defensive responses to the main goal of one design field in another.

There is great concern among urban designers, traffic designers and environmental engineers about the negative impact of traffic and infrastructure on urban areas. Because it affects the quality and vitality of the city. The urban designer's expectation of physical design in urban planning makes certain road patterns and pedestrian priority get attention, hoping that it will not affect traffic efficiency and traffic safety.

Overall, our research focuses on the interaction between transport supply and urban design, rather than a single issue entirely within these two areas. Therefore, within this framework, there will be two specific areas of focus. First, it will focus on the role of transport forms that can help achieve urban goals, including urban quality and vitality as well as sustainability. Second, it is natural to focus on possible points of contention when considering the interaction between the“main approach”and the“respons”. These arguments are effectively reflected in the response.

Firstly, there seems to be a consensus among disciplines that the destruction of cities must be avoided. Traffic planners and engineers today take the environmental impacts seriously and effectively and view them as parts of their concern that in the past, the urban consequences of road construction and other infrastructure interventions could be considered irrelevant or incidental.

Secondly, to some extent, extensive work has been done in this area, such as the entire field of environmental impact assessment. Similarly, the desire to maintain safety and efficiency is a frequent concern of transportation planners and engineers.

Urban planning designers in the design of the transportation infrastructure and urban route network structure and network design, have found that the creation of the design concept will help urban layout and optimization of settlements, but in terms of transportation function, giti on liquidity, in particular, the lack of promoting the quality of fine designer or urban planner.

It is not usually the responsibility of the traffic designer and the traffic engineer to effectively solve a series of problems in urban life, which is actually a whole problem in urban planning.

This has perhaps only managed to get underway since the mid 1990s, which explicitly links the design of built form with road layout considerations. Even so, to date, efforts seem to have not got far beyond recognition of the oblem2. This is therefore very much a contemporary and pressing issue, and one requiring attention.

1.2.4 Research Scope

Based on the current policies and practices of the UK as the research background and as a whole of urban design, this study was conducted in different countries and locations of different cities, including analysis of some cases from all over the world. Most of the design analysis, design principles and practical results of the study can be applied to different design concepts, not limited to the UK. This study starts from the traditional idea, the mixed use of modern road and comprehensive traffic, as well as the design layout of the traffic and pedestrian priority in residential areas, as a general discussion, thus promoting the innovative development concept, and does not make the design scope specific in the UK.

1.2.5 Scales of Consideration

The research mainly focuses on the scale of“urban blocks or blocks”, which is the typical scale of urban design considerations, between the scale of individual buildings that architects usually consider and the scale of complete settlements or traffic networks that strategic planners or traffic planners consider.

Form of the city, or part of the city, is considered to be more important than the overall shape and form a complete city or town, because in most cases, the urban construction gradually upward or outward, rather than the usual in creating a plan and execution behavior. Basically, the scale of the structure in design is the most effective analysis, as the structure and design process are intertwined. This usually means the size of the design block and quarter.

1.2.6 Focus on Roads and Streets

While the study is nominally about the supply of urban traffic, it will focus primarily on the street network, which combines the road network and the extended pedestrian network. These are major concerns because they directly constitute the public domain and are the main backdrop for most urban design.

Other networks, such as railways and waterways, are less important. While railways have a practical impact on urban structures（and can lead to urban destruction）, they are generally not in the public domain. Although waterways have an important influence on the formation of urban structures, the influence of traffic arteries is only a part, and the product of urban design is even less. In other words, these networks are less important to our current research. Railways and highways, too, are irrelevant to the topic, since their networks are often rough, meaning they tend to be only linear interventions at the local scale of urban design. Configuration, non -linear characteristics are reflected in local scale, such as route bifurcation, or the radial and orbital route between exchanges, which tend to be associated with larger demand patterns, such as the relationship between addressing the overall distribution of urban functions, or geographic settlements, rather than any generalisable configuration pattern. In contrast, there are enough generic roads and various types of streets, such as long, short, motorized and pedestrian streets, to justify their research, as they can be combined into different types of networks in multiple ways.

However, general“transport regulations”, rather than“road regulations”, are fully retained, since the inclusion of railways and certain other means can be implicitly considered within the scope of this paper.

1.2.7 Key Elements of Transport Modes

This study considers a variety of transportation modes and how these modes can adapt to the distinctive sustainable development concept of urban areas in terms of functional design.

In urban environments, every mode of transport takes up an“evolutionary factor”. The public transport system, for example, thrives in densely congested corridors, where competition is fierce in areas where traffic is not heavy. The penetration of the bus in the suburbs is more flexible, although it may have only minimal use in areas with the lowest population density. However, the car is well suited for the dispersed suburbs, and from a Evolutionary factor perspective, the car has also helped drive suburban development. Pedestrians are restricted to a certain extent and disadvantaged by long-distance traffic in the suburbs, but we can find a development market that no other model can match. Finally, we see how some models are“extinct”. This combine the disadvantages of low speed and fixed routes. It now exists only as a museum.

In some cases, new modes of transport have evolved to adapt to new urban conditions.

Bus Rapid Transit is a new public passenger transport system between Rapid Rail Transit and Normal Bus Transit. It is a unique urban passenger transport system that utilizes modern bus technology to cooperate with intelligent traffic and operation management（integrated dispatch system）, opens up bus special roads and builds new bus stations, realizes the operation service of rail transit mode and achieves the service level of light rail.

These latter cases represent solutions dealing with the ‘mobility-led'problem of serving urban areas with transport. However, the problem can also be approached from the other side: the design of the built environment. Physical planning（embodying urban design and transport provision）can change the‘ecosystem'of the different modes, as it were, to favor one type over another, whether by helping to ‘feed'public transport, or by differentially favoring routes for non-motorized modes, or, at least, by ensuring that there are plenty of convenient niches where walking and cycling can naturally flourish. It is this angle - the design of transport networks, in relation to urban structure, rather than direct treatment of systems of transport modes- that is the concern of this thesis.

Urban Traffic comes from urban land and comes back to urban land. The operation of social life and production activities between urban land use, as well as the connection between living, working and leisure activities have generated traffic activities, which requires a city transportation system to shoulder this task. The urban traffic system includes the urban road system, the urban transport system and the traffic management system, in which the transport system is the traffic operation network, the road and other facilities are the traffic access network, and the management system is the guarantee of the normal traffic operation. The urban traffic system depends on the dynamic relationship between urban land use, which reflects the dynamic functional relationship of the city. Transportation plays a core role in the four basic urban activities. Urban planning is not only a reasonable arrangement of urban living, work and open space, but also a guarantee of efficient and convenient transportation system. Urban traffic and road system planning（urban traffic system planning）is a core issue of urban planning.

The interpenetration of high-speed, long-distance and near-distance transportation systems makes the urban transportation system interact with each other, forming a multi-functional and comprehensive transportation system mode, which is also the prevailing mode at present. However, public transport and pedestrian transport do not necessarily provide the advantages of distance and crossing at the same time, so they are often complementary, forming a“replacement”system of cars together.

All levels of urban roads are the framework of the organization of the city, but also urban traffic channels, according to the layout of urban land and traffic intensity to arrange the layout of urban road network at all levels. The relationship between the nature and function of various roads（networks）in cities and the layout structure of urban land is shown as the functional layout of urban roads.

The rapid road network mainly serves medium and long distance traffic between urban groups and traffic services connecting expressways. It is advisable to arrange it in the separated green space between urban groups to ensure its speed and smooth traffic. The expressway is basically built into a city cluster, so its spacing depends on the size of the urban cluster in the urban layout structure.

The urban trunk road network is the road network throughout the city, mainly for the urban groups and the main traffic flow within the groups to the medium and long distance traffic services. In order to meet the needs of modern urban traffic motorization development, the urban traffic trunk road network should be laid out in the city, as the main channel of urban traffic and the main normal speed road connected with the express road. Urban traffic trunk roads are roughly grouped into one urban area, while other urban main roads（including living trunk roads and distributed backbone roads）are roughly grouped into one residential area.

The urban road network is a network within the urban cluster, which, together with the urban master road network, constitutes the basic framework of the city and the basic form of the urban road network, mainly serving the medium and short distance transport within the cluster. The road in the city is roughly the size of a residential community.

The city branch road is the road designated in the urban lot according to the traffic demand generated by the detailed arrangement of land use, which should be arranged in the detailed planning, and may form a net in the local section of the city（such as the commercial district, the residential area arranged by the neighborhood）, but cannot form a net in the city group and the entire urban area. Therefore, it is not possible to plan in the general regulation of the city, nor to calculate its density and quantity. In the detailed planning, the spacing of city branch roads mainly depends on the division of land.

Basically, the more focused the schema, the less flexibility. Meanwhile, the less power assist, the more limited range. As a result, scope and penetration are considered key attributes that affect traffic flexibility. Therefore, any attempt to optimize the structure of a city for a particular model will be directly related to the scope and flexibility of the model under consideration, among other considerations.

These points may be illustrated by means of a three-way‘monogram', where the car, the pedestrian and public transport represent three distinct extreme（Figure 1.2）.

Figure 1.1. The modal spectrum or‘monogram'.

Each model is drawn to an ideal degree of individualism and mechanization. Note that the green model favors this ideal model. The size of the drawing does not represent flexibility. In reality, each collective pattern will occupy a scope, not a point.

The study will also focus on the three“key”modes of transport - pedestrians, public transport and private cars - that are considered crucial in providing routes and their relationship to the urban form.

Other modes effectively fall within these extreme. For example, the bicycle is‘individualistic'like the car or the pedestrian; like the pedestrian it is non-motorized and limited in range to some extent - though not quite as limited or ‘slow'as the pedestrian, especially in urban areas, where it may be the fastest mode door-to-door. In some cases the cyclists'needs will be met by the vehicular traffic network（albeit, preferably with the vehicular traffic removed, in other cases their needs will more closely match those of the pedestrian. Where separate treatment would in practice be singled out（e.g., bicycle lanes or bicycle tracks）these would not appear to have much additional influence on urban structure. This is not simply in terms of relatively small proportions（in many western cities）of modes such as bicycles and motorbikes, but in their limited historical role in giving rise to distinctive types of urban form and structure, compared with, say, the classic cases of the historic compact city, the radial city or the dispersed car-oriented city.

For convenience the thesis will tend to refer to the three‘key modes'themselves（rather than the combinations of attributes that they represent）. Thus, references to the car will normally imply a variety of types of traffic, including many road freight traffic movements, for point-to-point journeys. On the other hand, some freight movements, such as serial deliveries, may be more aligned with the characteristics of public transport, as far as implications for optimal layouts are concerned. At the level of resolution considered in subsequent chapters, different forms of public transport are generally not differentiated, although clearly there will be a spectrum of types（bus, guided bus, light rail, rail etc）with slightly different requirements.