Urban experiments have been initiated in several locations to purposively initiate and shape transitions to more sustainable urban socio-technical systems, e.g. for energy, water, mobility. Although knowledges produced within such learning spaces are often presented as logical, technical and rational (Vanolo, 2013; Kitchin, 2014), the actors and mechanisms that shape decisions are far from obvious, involving cultures, power relations and multiple logics that are profoundly political (Machin, 2013). This research presents a case study founded in a phronetic perspective (Flyvbjerg, 2001; Avelino and Grin, 2017), unpacking the epistemological politics of an urban experiment taking place within a ‘smart city’ programme. A ‘smart transport’ application for mobile phones, ‘MotionMap’, was developed to transform the mobility system of Milton Keynes, an expanding city located 80 km to the north of London, UK. The case study recognises power relations and reveals how various actors engaged in the development of this application have further rendered the MK mobility socio-technical system an object of urban governance.