Future-proofing cities against negative city mobility and public health impacts of impending natural hazards: a system dynamics modelling study

BACKGROUND: The world faces increasing risk from more frequent and larger scale natural hazards, including infectious disease outbreaks (IDOs) and climate change-related extreme weather events (EWEs). These natural hazards are expected to have adverse mobility and public health impacts, with people living in cities especially vulnerable. Little is known about how transport systems can be optimally designed to make cities more resilient to these hazards. Our aim was to investigate how cities' transport systems, and their resulting mobility patterns, affect their capabilities to mitigate mobility and health impacts of future large-scale IDOs and EWEs. METHODS: System dynamics modelling was used to investigate how different city mobility scenarios can affect the health and mobility impacts of four plausible future IDO and EWE (flooding) shocks in three cities: Belfast, UK; Belo Horizonte, Brazil; and Delhi, India. Three city mobility scenarios with incremental degrees of modal shift towards active travel (private motor vehicle volume reduced to 50% and 20% of total road trip volume in vision 1 and 2, and motor vehicle volume [including buses] reduced to 20% of total road trip volume in vision 3) were tested. For each city and each IDO and EWE shock, we estimated the percentage of deaths prevented in visions 1, 2, and 3, relative to the reference scenario, as well as changes in mode share over time. FINDINGS: In all scenarios, all cities showed reduced susceptibility to flooding, with 4-50% of deaths potentially prevented, depending on case city, city mobility, and EWE scenario. The more ambitious the transition towards healthier city mobility patterns, the greater the resilience against flooding. Only vision 3 (the most ambitious transition) showed reduced vulnerability to IDOs, with 6-19% of deaths potentially prevented. Evolution of mode shares varied greatly across cities and mobility scenarios under the IDO shocks. INTERPRETATION: Our results emphasise the importance of well designed, forward-thinking urban transport systems that make cities more resilient and reduce the impact of future public health-related and climate-related threats. FUNDING: UK Prevention Research Partnership, UK Economic and Social Research Council, UK Medical Research Council, UK National Institute for Health and Care Research, Australian Research Council, Australian National Health and Medical Research Council, and Health and Social Care Research and Development Office Northern Ireland.