Current trends in urban planning aim at the reduction of space for private vehicles to promote alternative mobility, more diverse activities on streets and reduced pollution for healthier cities. Simultaneously, “tactical urbanism”, embedded within participatory processes, helps to articulate and enrich these policies.

In this connection, our study evaluates a number of “what-if scenarios” of “city pruning” by means of realistic, agent-based computer simulations. They regard traffic restrictions for Barcelona with the purpose to identify the impact on travel performance and the environment. Positive counterintuitive effects related to Braess and Daganzo paradoxes are found in new alternatives to the street repurposing plans developed by the City of Barcelona.

These result in a reduction of emissions (−8% of main pollutants) and traffic congestion (−14% of travel time) solely by closing some streets to motor vehicles. These findings indicate a formerly unnoticed potential to further improve the quality of urban life.

Hence, the use of interactive urban models can be a powerful tool to explore and co-create policies within participatory approaches in spatial planning. Positive counterintuitive effects of street repurposing and network dismantling provide opportunities for participatory and sustainable city-making beyond the ongoing public debate.

J.A. Sanchez-Vaquerizo, D. Helbing, Less can be more: Pruning street networks for sustainable city-making, Transportation Research Interdisciplinary Perspectives 21 (2023) 100878.