This chapter examines the political capacities of Shared Streets experiment in the promotion of smart and sustainable cities. By describing the contingencies and controversies that emerged as a result of the efforts to 'laboratorise' the urban space towards low-carbon habits, it contributes to the discussion of how 'smart citizen' projects are translated and operationalised in specific contexts such as Santiago de Chile. The chapter analyses how the use of ideas of citizen participation and urban laboratories – which are being increasingly included in smart city strategies around the world – constitute true socio-material devices for justifying and legitimating institutional interests while limiting other modes of experimentation and smartness. To complement the narrative, political and technological aspects behind smart cities, it highlights two closely linked concepts: namely the 'experimental' and 'citizen' grammars that are increasingly infused into smart city programmes and their implications in cities of the Global South.