Beyond "15-minute cities", the need to connect at the agglomeration scale

Barcelona has been at the forefront of the global 15-minute city movement, pioneering the concept and implementation of superilles (superblocks) since 2014. As Lamiquiz et al. (2025) highlight, the city’s evaluation of superblocks’ impact led to a significant evolution in its 2024 Mobility Plan (PMU): the introduction of agglomeration-scale green axes (Ejes Verdes), designed to connect superblocks into a cohesive network.

"Ejes verdes" (green axis), supplementing the "superilles" (15-minute cities inspired superblocks) in Barcelona urban planning (PMU) from 2024 (Ajuntament de Barcelona, Superilla Barcelona—Model Eix Verd. El nou carrer del segle XXI. 2021)

What’s particularly compelling is how Barcelona’s superblocks — local implementation of the 15-minute city model — are now being complemented by this longer-distance network approach. This resonates with the classic Transit-Oriented Development (TOD) corridors, as in the necklace of pearls idea (Arrington et al 2008, p 73). After all, Calthorpe (1993) himself introduced TOD after first theorizing the pedestrian pocket, underscoring that urbanism is, by definition, multi‑scale.

This development also enriches the broader debate on 15-minute cities. In February 2024, I had the opportunity of joining Carlos Moreno on a guided tour of Paris’s Olympiades-Batignolles district, a model 15-minute neighbourhood. Standing outside the iconic Pont-Cardinet metro station, I asked Carlos about the role of transit in the 15-minute city framework — and its connection to TOD. His response was clear: transit should remain secondary in the model, with the primary focus on proximity.

The Pont Cardinet metro station in Olympiades-Batignolles district, Paris (CC-BY-SA Cartocite, Mapillary, 2021)

The convergence — and divergence — of these urban models is fascinating. In Barcelona, the green axes (or streets for the 21st century) prioritize walking, cycling, and placemaking, while explicitly integrating public transport planning. This holistic policy suite outlines the contours of an urban model that warrants further research — and perhaps even theoretical formalization.

References

• Ajuntament de Barcelona (2021). Superilla Barcelona—Model Eix Verd. El nou carrer del segle XXI. https://ajuntament.barcelona.cat/superilles/sites/default/files/SuperillaBarcelona_Presentacio_CarrerSegleXXI.pdf
   
• Arrington, G. B., and Robert Cervero. Effects of TOD on Housing, Parking, and Travel. No. 128. TCRP Report. 2008. http://www.reconnectingamerica.org/assets/Uploads/finalreporttcrp128.pdf.
• Calthorpe, Peter. The next American Metropolis: Ecology, Community, and the American Dream. Princeton Architectural Press, 1993.
• Cervero, Robert. The Transit Metropolis, a Global Inquiry. Island Press, 1998.
• Lamíquiz-Daudén, P. J., Baquero-Larriva, M. T., Ramirez-Saiz, A., & Carpio-Pinedo, J. (2024). Proximidad y herramientas de planificación en España: los casos de Barcelona, Castelló de la Plana, Pontevedra, Valladolid y Vitoria-Gasteiz. Ciudad Y Territorio Estudios Territoriales, 56(220). https://doi.org/10.37230/CyTET.2024.220.17