Urban living labs as cracks, not doors: Reimagining experimentation in transport (and beyond)

Urban Living Labs (ULLs) are widely promoted as experimental spaces for urban innovation, particularly in EU policy contexts. Yet their design is often shaped by current institutional logics, EU-funding structures, and sector-specific constraints, especially in transport, a domain marked by technical path dependencies and dominant narratives of efficiency and optimization. These conditions risk narrowing experimentation. This Viewpoint is written within the frame of the special issue Urban Living Labs and inclusive, accessible and sustainable transport systems . It critically reflects on the role of ULLs in shaping mobility futures, drawing on Báyò Akómoláfé's metaphor of doors and cracks. In the words of Akómoláfé “doors are anticipated architectural technologies” - they allow movement, but only within the logic of the existing structure. Cracks, by contrast, are unruly and unpredictable; they open towards the unknown. Thinking with Akómoláfé's metaphor, we ask: what remains unseen when experimentation in ULLs becomes an overly programmed or top-down process - when the lab becomes a door that opens in predefined buildings and structures? This paper reflects on the potential of cracks, and how subtle, disruptive, and often overlooked experiments can emerge beyond what can be seen in formal ULLs. Against this backdrop, we argue for a reformulation of the Urban, the Living, and the Lab that recognizes cities as contested and relational, and centres future experimental interventions in lived experience, care, and refusal. This reframing also calls for new theories of change that may potentially emerge through increasing reflexivity and historical awareness, more attentive listening, and engaging with the unpredictable.