Amid rising congestion and transport emissions, policymakers are embracing the "15-minute city" model, which envisions neighborhoods where basic needs can be met within a short walk from home. Prior research primarily examined amenity access without examining its relationship to behavior.

We introduce a measure of local trip behavior 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, signaling potential socio-economic challenges in achieving local living.