Imagine a Walkable City: Physical activity and urban imageability across 19 major cities

Can the shape of a city promote physical activity? The question of why individuals engage in physical activity has been widely researched, but that research has predominantly focused on socio-demographic characteristics (e.g., age, gender, economic status) and coarse-grained spatial characteristics (e.g., population density), overlooking key urban characteristics of, say, whether a city is navigable or, as urban theorist Kevin Lynch put it, whether it is ‘imageable’ (whether its spatial configuration is economic of mental effort). That is mainly because, at scale, it is neither easy to model imageability nor feasible to measure physical activity. We modeled urban imageability with a single scalable metric of entropy, and then measured physical activity from 233K wearable devices over three years, and did so across 19 major cities in the developed world. We found that, after controlling for greenery, wealth, walkability, presence of landmarks, and weather conditions, the legibility hypothesis still holds: the more imageable a city, the more its dwellers engage in physical activity. Interestingly, wealth (GDP per capita) has a positive association with physical activity only in cities with inclement climate, effectively acting as a compensation mechanism for bad weather.