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This paper investigates how land use relates to greenhouse gas emissions, using data sources that are readily available to municipal planners. It presents a causal framework linking settlement patterns to greenhouse gas emissions via landscape impacts (deforestation, carbon sequestration by soils and plants, urban heat island), infrastructure impacts (transportation-related emissions, waste management-related emissions, electric transmission and distribution losses) and buildings (residential, commercial). This is not a full accounting because it does not include impacts from industrial activities, agriculture and consumer behavior not related to land use, such as food consumption and air travel. Exploratory case studies of municipalities lying along a gradient of increasing population density suggest that per-capita carbon dioxide emissions vary widely, following an inverted 'U' shape, with post-war suburbs riding the pinnacle. Reflecting their central regional roles, municipalities with good jobs-to-housing ratios have higher per-capita emissions because they host both residential and commercial buildings. Buildings typically contribute more emissions than personal transportation. Vehicle-miles traveled per capita shrink most dramatically at very high population densities and where transit options exist. Changing land-use patterns is a political challenge because localism and outdated zoning ordinances subvert regional solutions. Technical fixes, especially green buildings, must be part of the solution. [ABSTRACT FROM AUTHOR]

The carbon dioxide (CO 2) emissions characteristics of urban roads together with the corridors' municipal construction subprojects, such as drainage, water supply, power pipeline and illumination, are important for estimating the CO 2 emissions for urban transportation. This paper aims to analyze the differences in the CO 2 emission characteristics of one typical construction of Chinese urban road corridor in which the structure, materials and technologies are different with other published cases, to identify the important factors of the CO 2 emissions and to provide some improving administration suggestions for the research type road. Choosing an example, which is the main urban road (Qinling) reconstruction project in Xi'an city, the documents of construction organization and the design budget estimation of the road are obtained, collected the construction process, machinery type and work time, and transportation distance as three type engineering quantities from five subprojects. Furthermore, the life-cycle assessment (LCA) and uncertainty analysis were applied for Qinling road corridor. The results are: (1) The CO 2 emissions of the road subproject accounts for 53.19% of the whole corridor; (2) The CO 2 emissions of the lime-fly ash, cement and lime accounts for 26.86%, 19.59%, 15.3% of the whole corridor respectively; (3) The CO 2 emissions of on-site transportation, earth work, road building, hoisting accounts for 4.94%, 2.07%, 1.47%, 0.74% of the whole corridor, respectively; (4) The greater CO 2 emissions coefficient of elasticity are from the production of lime, cement and asphalt concrete, which is 0.436, 0.134 and 0.125, respectively; (5) Compared with Route 35 reconstruction in New Jersey, the CO 2 emissions of Qinling road corridor is 41.5 kg/m2 higher because of the important role of lime-fly ash base layer. To conclusion, important strategies are to decrease the emissions of production of lime and cement, to controll the ineffiecient movement of machinery, and to adopt cleaner materials in the base layer. [ABSTRACT FROM AUTHOR]