In Europe, for the past several decades, we have observed that local urban transportation policies in many cities have been geared at reducing automobile use; at the same time, mobility has become a key aspect of social integration. The massive development policies of public transportation systems which, among other things, aim at guaranteeing this mobility in spite restrictions against automobile use nonetheless are not always a sufficient response to this. Based on this more or less paradoxical idea, the goal of this thesis is to highlight the link between daily mobility behaviours of vulnerable populations and urban transit policies in these cities over the past decades. More specifically, we will look at the two-fold question of 1) how does the spatial distribution of functions in a given region and the means of accessing them influence individuals' mobility capacity and 2) which transportation and development policy produces which inequalities when it comes to mobility? We have chosen to tackle these issues comparatively by looking at two cities in Switzerland (Geneva and Bern) and two in France (Clermont-Ferrand and Grenoble), cities characterized both by diverse urban configurations in terms of density, compactness and locations, and yet with accessibilities (by car, foot or public transportation) that are quite different.