Effects of Spatial Structure on Air Quality Level in U.S. Metropolitan Areas

The purpose of this dissertation is to investigate relationships between metropolitan spatial structure and air quality across U.S. metropolitan areas. Debates over compact city and sprawling development models as alternative patterns of metropolitan development and planning remain unsettled. This dissertation works from the hypothesis that compact regions with high-density, concentration, mixed land use, and better accessibility improve air quality. To test the compact city hypothesis, this dissertation uses a combined spatial data of population, employment, government, land use, and air quality in 610 counties in U.S. metropolitan areas and their neighboring areas for 1990, 2000, and 2006. Indicators identified widely in literature are employed to measure compact city: land uses, density, concentration, accessibility, and centralization. This dissertation provides the empirical evidence on the basis of some stipulated causal relationships between compact regions and air quality through multivariate regression models using spatial econometric analysis, that sheds light on the presence of spatial dependence between spatial variations in alternative spatial structures and changes in air quality level. The empirical results show a number of interesting signs to the compact city hypothesis. Metropolitan areas with a higher percentage of developed open space or longer weighted average daily commute time bring out higher average air quality index values, leading to worsened air quality. On the contrary, metropolitan areas with a higher percentage of densely employed sub-areas produce lower average air quality index values, resulting in improved air quality. The empirical findings contribute to the importance of compact development strategies, such as polycentric employment centers, on improved air quality over suburban sprawl in the United States towards successful sustainable metropolitan development and plannin