In recent years, many cities have embraced the 15-minute city concept (15minC) by implementing strategies to foster both urban density and diversity, reducing car traffic through car-reduced neighbourhoods and re-designing urban street spaces. However, many cities adopting the approach are experiencing public and political backlash. One reason is that the concept is seen as disproportionately benefitting urban residents while ignoring the needs of those living in the periphery. To overcome these transition conflicts, cities need to find solutions to expand the 15mC concept beyond the urban core while making it more socially inclusive. To address this knowledge gap, TuneTo15 combines quantitative accessibility analysis with qualitative analysis of social conflict dimensions in four international case studies. The goals of the project are: (1) to identify the limits and potentials of the 15mC concept in diverse spatial settings, especially beyond the urban core; (2) to understand the impacts of the concept on different social groups and identify conflicts between them; and (3) to engage municipal stakeholders in co-creative processes to develop implementation and conflict-resolution guidelines. A key element is the “Municipal Peer Group”, which fosters peer-learning and helps to build transformational capacity in city administrations and other stakeholders of urban transition processes.