The Relationship Of Road Network And Urban Efficiency Based On Scaling Law

China has the fastest economic growth, and is also the fastest urbanizing area in the world. City is a complex system, and there are many types of interactions in the city. Social interaction creates socioeconomic output(such as GDP), but also brings infrastructural costs.Explore the law of urban development, quantitative expression of urban efficiency, and provide theoretical basis and decision-making support for urbanization is the focus of urban studies. This papermakes use of multi-source data, including statistical yearbook, DMSP/OLS nighttime light data, and floating car data, combines qualitative and quantitative analysis to explore the law of urban development and urban efficiency from 3 scales: the national scale, mega-region scale and within city scale. In the national scale, based on the latest research results of quantitative urbanism, explore the applicability of scaling law and social-tie density model in China. On the one hand, this study applies the scaling law to Chinese cities and retrieves the exponent and constant of the scaling law of population and urban indicators taken from statistical yearbook, analyzes the trend of the overall level of urbanization year by year, the result shows that the development of Chinese cities is gradually mature.On the other hand, using social-tie density model to analyze the relationship between the urban characteristics per unit area and urban population density; to computethe efficiency of urban development in China more objectively and more intuitively, the Night Light Urban Efficiency Index(NLUEI) is proposed, this index is simple, objective and easy to use.In the mega-region scale, taking Beijing-tianjin-hebei urban agglomeration as an example, network efficiency and local efficiency of each city are analyzed, to quantitatively express the link between road network and the entire urban agglomeration, and analyze the interaction between individual city’s location, transportation with that of the urban agglomeration.In the within city scale, traffic affects people’s travel, and influences the activeness of people’s interaction and cost, in the urban morphology framework, analyze the effect of road network’s morphology and structure on traffic in Beijing using space syntax, then use the actual floating car data to verify.The results are as follows:1) In the national scale, in the scope of “urban road traffic planning and design standards(GB50220-95)”, GDP per capita has positive correlation with road length per capita, the optimal urban efficiency can increase along with road length(area) per capita, other methods that could promote the social tie could also provide the possibility of improving the efficiency of city.2) G is defined as the product of road area(length) and GDP, both per capita. The G-Population scatter diagram is in the shape of an inverted triangle. For a city system(country), under the premise of normal city size distribution, the smaller the area of the triangle becomes, the higher the efficiency of the whole system will be.3) NLUEI(Night Light Urban Efficiency Index) can quantitatively evaluate the urban efficiency. The higher the Night Light Urban Efficiency Index is, the greater the urban efficiency is.2) At mega-region scale, the cities in Hebei province have little influence on the efficiency of the Beijing-tianjin-hebei urban agglomeration. In order to achieve coordinated development, we should make the connection among the other cities easier.3) In the within city scale, analyzing the characteristics of the roads which are often congested from the view of Space Syntax, they have very low mean depth and total depth, but relatively high global integration, local integration, control, length, local depth and connect.