The objective of ARTS is to benefit policy, practice and theory related to accelerating sustainability transitions and to create opportunities for innovation (including social innovation) by coupling, rescaling and accelerating sustainability initiatives in European city-regions. ARTS will create interfaces between policy, practice and theory that are spaces for co-creation, theory building, policy experimentation, social innovation and learning. ARTS will have an aggregated impact on transition regions, on national and European policy related to facilitating transitions, and on theory and governance of sustainability transitions. The focal unit of analysis will be innovative activities and related actor-networks that are fundamentally changing energy, food, shelter and mobility provisioning patterns at the scale of a city or region, situated within a wider European context. ARTS will explore how lessons from these initiatives can be drawn for broader transitions to sustainable low-carbon European societies. We seek to identify the values, conditions and mechanisms for accelerating sustainability transitions, develop strategies to assist and stimulate their acceleration and assess them with dynamic modelling approaches. We will explore these conditions based on a diverse set of transition initiatives in five regions across Europe in an inter- and transdisciplinary way: Brighton, Budapest, Dresden, Flanders, and Stockholm. The developed acceleration governance approach and modelling platform, support decision making, and social learning processes to speed-up the implementation of EU’s Sustainable Development and Biodiversity Strategies. They deliver to the energy targets (20/20/20 targets, the EU Energy Strategy), and the targets addressed in the Roadmaps (2050-Competitive Low-carbon Economy, Resource Efficient Europe), while supporting transitions to innovative (Innovation Union Flagship Initiative) socially sustainable (2020 Growth Strategy) low-carbon societies.