The COVID-19 pandemic has recently forced half of humanity to experience an unprecedentedly expansive lockdown. Naturally, this has brought urban transport systems under a near standstill, which in turn resulted in a sharp drop in carbon emissions and levels of air pollution in affected areas. While the induced health and economic crisis is already lasting longer and affecting many more than originally expected, questions arise on what that means for the future of urban living, urban design and connectivity. A post-COVID-19 city could notably see a sustained drop in demand for commuting transport due to a combination of enduring economic crisis and changing work habits. It could experience a behavioural shift with regard to crowded spaces, and public transport in particular. In such context, this snapshot piece aims first at examining the possible consequences on public health of this scenario. Secondly, it uses system thinking to evaluate how stimulus plans could maximise social, health and climate co-benefits. It takes the example of populous middle-income countries to suggest a shift to investing in infrastructure focused on active travel modes, as the most prone to cheaply sustain hygiene, social-equity, reduced exposure to air pollution, reduced numbers of fatal accidents, and enhanced levels of physical activity.