Limits to sustainability in pedestrianized public spaces. Administrative constraints and unintended uses in Barcelona's green axes

The global pursuit of sustainable cities has led local governments worldwide to reform public spaces, shifting from car-centric infrastructures towards pedestrian-oriented settings. While such interventions have gained widespread acceptance, little attention has been paid to how pedestrians actually use these redesigned public spaces or whether the resulting built forms align with the sustainability goals articulated in the original urban design intentions. This paper addresses this gap by advancing architectural ethnography as a methodological lens for assessing public-space sustainability, treating pedestrian mobility data not as a neutral technical output but as an integral component of urban design and planning processes. Using the Consell de Cent green axis in Barcelona as a case study, the paper examines the institutional production and everyday inhabitation of a flagship pedestrianization project that has served as an international reference through the superblock model. Empirically, the study combines ethnographic observations in public space with interviews with architects and residents, analysis of institutional documents regulating urban design and land-use frameworks, and an examination of ground-floor commercial transformations following pedestrianization. The findings provide empirical evidence of how administrative and regulatory frameworks constrain ecological ambitions during design-making, while revealing the emergence of unanticipated commercial typologies, everyday uses, and mobility patterns. These dynamics expose structural limits to public-space sustainability that are not fully captured by post-occupancy design-led evaluations. The paper concludes by arguing that advancing sustainable public spaces requires a critical perspective that foregrounds planning externalities and unplanned uses when rethinking the scope and limits of people-centered contemporary urban interventions.