The 15-minute city quantified using human mobility data.

Amid rising congestion and transport emissions, policymakers are embracing the '15-minute city' model, which envisions neighbourhoods where basic needs can be met within a short walk from home. Prior research has primarily examined amenity access without exploring its relationship to behaviour. We introduce a measure of local trip behaviour using GPS data from 40 million US mobile devices, defining '15-minute usage' as the proportion of consumption-related trips made within a 15-minute walk from home. Our findings show that the median resident makes only 14% of daily consumption trips locally. Differences in access to local amenities can explain 84% and 74% of the variation in 15-minute usage across and within urban areas, respectively. Historical data from New York zoning policies suggest a causal relationship between local access and 15-minute usage. However, we find a trade-off: increased local usage correlates with higher experienced segregation for low-income residents, signalling potential socio-economic challenges in achieving local living.

Spatial proximity matters: A study on collaboration.

As scientific research becomes increasingly cross-disciplinary, many universities seek to support collaborative activity through new buildings and institutions. This study examines the impacts of spatial proximity on collaboration at MIT from 2005 to 2015. By exploiting a shift in the location of researchers due to building renovations, we evaluate how discrete changes in physical proximity affect the likelihood that researchers co-author. The findings suggest that moving researchers into the same building increases their propensity to collaborate, with the effect plateauing five years after the move. The effects are large when compared to the average rate of collaboration among pairs of researchers, which suggests that spatial proximity is an important tool to support cross-disciplinary collaborative science. Furthermore, buildings that host researchers working in the same or related fields and from multiple departments have a larger effect on their propensity to collaborate.