A comparison of the health and environmental impacts of increasing urban density against increasing propensity to walk and cycle in Nashville, USA

ABSTRACT

The transportation sector accounts for approximately 23% of the total energy-related carbon dioxide (CO₂) emissions worldwide and 33% in the USA. At the same time, physical inactivity contributes to adverse health through non-communicable diseases. If policies can increase active transport (walking and cycling) and reduce car use, they could benefit human health and environmental health but the relative impact of different approaches has been under researched. This study estimated change in all-cause mortality and CO₂ emissions in greater Nashville, Tennessee (USA) for two scenarios: (a) the propensity to walk and cycle a trip of a given distance increases directly to the same levels as seen in England, and (b) walking and cycling trips increase and travel distance decrease indirectly as a result of a more compact urban form. If the propensity to walk and cycle in Nashville were equal with England, about 339 deaths and about 36 ktCO₂e (1%) of transportation-related CO₂ emissions could be avoided per year. The compact urban form scenario could avoid 170 deaths and 370 ktCO₂e (10%) of transportation-related CO₂ emissions. In Nashville, both increasing the propensity to use active transport and more compact urban form would have notable public health gains, but a more compact form would have a much bigger effect on emissions.

KEYWORDS:

• Active transport
• physical activity
• CO₂ emissions
• comparative risk assessment
• USA
• policy learning

This article is related to:

Research for city practice

Acknowledgments

Authors acknowledge feedbacks received at the Cities and Climate Conference, 2017, Potsdam (Germany). Thanks to Leslie Meehan, Rochelle Carpenter, and Geoffrey Whitfield for data and feedback and Brian McCabe for writing advise on earlier versions of this paper. Thanks to Mike Thompson Nashville Civic Design Center for Nashville’s images (Figure 5).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

Supplemental data for this article can be accessed here

Additional information

Funding

SA acknowledges the support from Alexander von Humboldt Foundation and the Federal Ministry for Education and Research (Germany) for the research fellowship. SA was also supported by Centre for Sustainable, Healthy and Learning Cities and Neighbourhoods, which is funded via UK Research and Innovation, and administered through the Economic and Social Research Council, as part of the UK Government’s Global Challenges Research Fund. MT and JW: The work was undertaken by the Centre for Diet and Activity Research (CEDAR), a UKCRC Public Health Research Centre of Excellence. Funding from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research, and the Wellcome Trust (MR/K023187/1), under the auspices of the UK Clinical Research Collaboration, is gratefully acknowledged. MT and JW were also supported by METAHIT, an MRC Methodology Panel project (MR/P02663X/1). The views presented in this paper are those of the authors, and do not necessarily represent those of the study funders or those providing feedback. Funders had no role in designing, conducting and reporting the study.

Notes on contributors

Sohail Ahmad

Dr Sohail Ahmad is a Research Fellow in GCRF Centre for Sustainable, Healthy and Learning Cities and Neighbourhoods (SHLC). Ahmad investigates low-carbon urban development options and socio-spatial exclusion issues in built environments and housing in south Asian cities. These empirical studies have extensively employed (spatial) econometrics analyses using Stata and R on large datasets. Prior to joining SHLC, he was an Alexander von Humboldt Research Fellow at the Mercator Research Institute on Global Commons and Climate Change, Berlin with join affiliation to the Technische Universität Berlin

Anna Goodman

Dr Anna Goodman works in transport and health topics, with a particular focus on sustainable travel. She is particularly interested in how secondary analysis of routine datasets can be use to evaluate existing interventions and model the impacts of potential interventions. Anna is based at the London School of Hygiene and Tropical Medicine

Felix Creutzig

Professor Felix Creutzig is head of the Land Use, Infrastructures and Transport working group and Chair of Sustainability Economics at Technische Universität Berlin. He was lead author of the IPCC’s Fifth Assessment Report and lead analyst of the Global Energy Assessment. His research focuses on (a) conceptualizing, quantifying and assessing mitigation potential for GHG emissions in cities world-wide, (b) building models of sustainable urban form and transport, (c) land rents as a complement for financing sustainable infrastructures, (d) analyzing the role of capital stocks and infrastructures for climate change mitigation, and (e) land use-mediated uncertainty in integrated assessments

James Woodcock

Dr James Woodcock is a European Research Council (ERC) Consolidator Grant holder. He leads a programme of work on transport and health modelling at the University of Cambridge, and has published extensively in both leading health and transport journals. Key achievements include the ITHIM suite of tools, the Propensity to Cycle Tool, and WHO HEAT tool.

Marko Tainio

Dr Marko Tainio studies transport, environment and health. He is using modelling methods, especially Health Impact Assessment, to estimate environment and health effects of urban transport policies. Marko has recently joined in the Sustainable Urban Programme in Finnish Environment Institute (SYKE), Finland, as Principal Researcher