This article explores the centrality of mobility in the practices of the outdoor advertising industry, analysing how commercial conceptualisations of mobility orient the production and sale of advertising space on roadside billboards, panels in pedestrian zones, on buses and taxis, and in train stations. I explore how the industry's market research practices conceive of urban space as mobility, and how understandings of mobility impact upon the design of advertising structures and their textual content. I conceptualise as a retroduction the relationship between market research practices, the aesthetics of advertising design and the visual engagement of people with advertisements. This is a performative relationship that produces a commercial ontology of the city. These retroductive relationships do not merely reproduce the hegemony of an urban commodity culture; they open up alternative ways of knowing the city.