Thesis: Three of the largest social unrests of the last two decades in France – the 2005 suburban riots, the 2013 Bonnets Rouges and the 2019 Gilets Jaunes movements- were directly associated with claims for spatial justice. It is actually no surprise that equity claims could take a spatial form and involve transportation. Cities are highly unequal structures, being the site of a spatial competition for access to the benefits of density. Transportation infrastructures, and especially public transit, plays a major role in organizing spatial inequalities, since they provide distant land with access to urban agglomeration economies. Without access to transportation, one could not enjoy a full citizenship. Two types of equity issues may be at stake in the spatial economy. Vertical equity, that regards equal treatment between households with different resources, is particularly salient within cities, since the housing market sorts incomes by distance to amenities and agglomeration economies. Horizontal equity, that regards equal treatment between households with similar resources and income, is of particular concern between cities, since the availability of transportation infrastructure, and especially public transport, conditions access to urban benefits for many urbanites. In a context of reinforced urban segregation, acceleration of the concentration of activity and jobs in large metropolis, and rise of transportation costs that could result of the generalization of the carbon tax, such vertical and horizontal equity claims may become more salient in the next decades. This thesis examines three aspects of spatial equity, through the particular scope of transportation infrastructure. The first two chapters assess whether public transit investment should be directed to mitigate vertical equity claims within cities or horizontal equity claims between cities. The third chapter applies the reflections of the first two chapters to the specific case of the fuel carbon tax acceptability and wonders whether urban policies could answer spatial equity issues associated with such a tax.