Over the last few years, smart cities have been a focus of scholarly attention. Most of these critical studies concentrated on the multinational corporations’ discourses and their implications on urban policies. Besides these factors, however, the data-driven city develops within a complex web of entanglements whereby data-driven technologies modulate the urban infrastructure in a multitude of ways contingent upon the social, political, material and technical aspects. As such, this article attends to the infrastructural implications of a smart city product, Citymapper, (...) which is a transport app built on open data available as part of London’s smart city planning. In order to establish the relationship between data and infrastructure, I use Gilbert Simondon’s notions of ‘transduction’, ‘individuation’ and ‘technicity’ to explore this relationship in a processual and relational way. In constructing this relationship as co-generative, whereby infrastructure and data transindividuate, I subsequently posit the term data/infrastructure. Against this theoretical background, I study the ways in which Citymapper individuates and thereby gains infrastructural power through technicity of data by studying the ways in which the users’ contribute to data generation that feed back into the app. Specifically, by following the transformation of the app from initially mediating the bus timetable to transducing users into environmental sensing nodes through which the app collects behavioural data, I foreground the epistemological, infrastructural and social consequences of Citymapper’s infrastructural power for the data-driven city. (shrink)