Urban Planning, Low-Carbon Transportation, and Health
An interdisciplinary household survey in the city of Chengdu, led by Chris NIELSEN (Harvard-China Project), James HAMMITT (Harvard T.H. Chan School of Public Health), and SHEN Mingming and YAN Jie (School of Government, Peking University), was completed in July 2016. The data have been joined with an earlier dataset collected in a nearly identical Harvard-China Project-PKU survey in 2005, to cover changes in Chengdu's economy, urbanization, travel behavior, land use, air quality, and environmental health over 11 years. In addition to this multi-faceted research on Chengdu, the Project conducts additional individual studies of transportation, land use, emissions, air quality, and/or health at urban scale.
Both the 2005 and 2016 Chengdu surveys collected data across a wide range of research interests, including transportation planning, travel behavior, mobile-source emissions, outdoor and indoor air pollution exposures, health effects of air pollution, and perceptions and valuation of health risk. Harvard researchers devised the questionnaires and are leading a number of parallel analyses. Covering 2000 households, field implementation of both surveys was led by political scientist Shen, using RCCC's rigorous geospatial sampling methods to insure inclusion of non-registered migrants left out of most social surveys in China.
Joining Hammitt and Nielsen in ongoing analyses of the datasets are China Project research affiliates GUAN ChengHe (Graduate School of Design, Harvard), Sumeeta SRINIVASAN (Department of Urban and Environmental Policy and Planning, Tufts University), WANG Haikun (School of Environment, Nanjing University), and GENG Fangli (Harvard T.H. Chan School of Public Health).
China started to implement comprehensive measures to mitigate traffic pollution at the end of 1990s, but the comprehensive effects, especially on ambient air quality and public health, have not yet been systematically evaluated. In this study, we analyze the effects of vehicle emission control measures on ambient air pollution and associated deaths attributable to long-term exposures of fine particulate matter (PM2.5) and O3 based on an integrated research framework that combines scenario analysis, air quality modeling, and population health risk assessment. We find that the total impact of these control measures was substantial. Vehicular emissions during 1998–2015 would have been 2–3 times as large as they actually were, had those measures not been implemented. The national population-weighted annual average concentrations of PM2.5 and O3 in 2015 would have been higher by 11.7 μg/m3 and 8.3 parts per billion, respectively, and the number of deaths attributable to 2015 air pollution would have been higher by 510 thousand (95% confidence interval: 360 thousand to 730 thousand) without these controls. Our analysis shows a concentration of mortality impacts in densely populated urban areas, motivating local policymakers to design stringent vehicle emission control policies. The results imply that vehicle emission control will require policy designs that are more multifaceted than traditional controls, primarily represented by the strict emission standards, with careful consideration of the challenges in coordinated mitigation of both PM2.5 and O3 in different regions, to sustain improvement in air quality and public health given continuing swift growth in China’s vehicle population.
In China a centralized planning culture has created similar neighborhoods across the country. Using a survey of 1,048 individuals conducted in 2016 in Chengdu—located in a carefully conceptualized typology of neighborhood forms—we analyzed the associations between individual and neighborhood characteristics and active or non-motorized transport behavior. Using several multiple logistic and multi-level models, we show how neighborhoods were categorized and the number of categories or neighborhood types affected the magnitude of the associations with active transport but not the direction. People taking non-work trips were more likely to use active compared with motorized modes in all neighborhood types. Neighborhood type was significant in models, but so were many other individual-level variables and infrastructural and locational features such as bike lanes and location near the river. Of the 3-D physical environment variables, floor area ratio (a proxy for density) was only significant in one model for non-work trips. Intersection density and dissimilarity (land use diversity) were only significant in a model for work trips. This study shows that to develop strong theories about the connections between active transport and environments, it is important to examine different physical and cultural contexts and perform sensitivity analyses. Research in different parts of China can help provide a more substantial base for evidence-informed policy-making. Planning and design recommendations related to active transport need to consider how neighborhoods, built environments, and personal characteristics interact in different kinds of urban environments.
In this paper, we discuss walkable cities from the perspective of urban planning and design in the era of digitalization and urban big data. We start with a brief review on historical walkable cities schemes; followed by a deliberation on what a walkable city is and what the spatial elements of a walkable city are; and a discussion on the emerging themes and empirical methods to measure the spatial and urban design features of a walkable city. The first part of this paper looks at key urban design propositions and how they were proposed to promote walkability. The second part of this paper discusses the concept of walkability, which is fundamental to designing a walkable city. We emphasize both the physical (walkways, adjacent uses, space) and the perceived aspects (safety, comfort, enjoyment), and then we look at the variety of spatial elements constituting a walkable city. The third part of this paper looks at the emerging themes for designing walkable cities and neighborhoods. We discuss the application of urban big data enabled by growing computational powers and related empirical methods and interdisciplinary approaches including spatial planning, urban design, urban ecology, and public health. This paper aims to provide a holistic approach toward understanding of urban design and walkability, re-evaluate the spatial elements to build walkable cities, and discuss future policy interventions.