Our thesis investigates the expansion of urban traffic from the early 1910s to the late 1960s. Initially built around the case of Lyon, one of the major French cities nowadays, the study also refers to the situation of others places -namely Marseille, Lille, Bordeaux, Nice, Saint-Etienne and Villeurbanne- in order to further underline the specificities -or lack of- of the city of Lyon. Not only does it rely on municipal archives, but also on national and international archives and periodicals issued by either public authorities or private bodies. Two main themes of interest structure the dissertation: the social construction of a public problem and the related regulation of public intervention. We investigate them through the study of local...