Abstract : When envisioning the future of a territory, public authorities typically make an effort to anticipate changes in land-use and transport systems. These projections are based on the principle that different zones are complementary, as they have varying urban functions. These differences generate transport demand, which then leads to concrete transport flows. Land use and transport forecasts are often carried out independently despite the well-known interactions between these two domains. The Greater Paris Area has pursued a polycentric New Town policy for over a generation, seeking an optimal spatial distribution of human activities. These New Towns were located in "preferential urban growth" zones served by major transport infrastructures in hopes of increasing the urban region's geographic coherence and better managing transport demand by reducing congestion toward the centre city and increasing public transit's mode share. Nonetheless, recent analyses of land-use data and mobility behaviour reveal that Greater Paris still possesses a dominantly monocentric urban form. The New Towns remain dependent on central Paris, and the private car is still the favoured transport mode; these areas never attained the degree of importance and centrality called for in the initial development plans. In order to verify the polycentric urban form's capacity to foster sustainable mobility, our thesis investigates two scenarios for urban development over the 2004-2030 period. Both involve increasing urban density, but this increase is spatially homogeneous in one scenario and more targeted in the other, with human activities clustered near urban subcentres. We carry out an integrated land-use and transport simulation, employing a supply and demand model from the DRIEA-IDF (Regional Direction for Infrastructure and Spatial Planning), as well as spatially focussed demographic projections based on the OMPHALE model from INSEE (the National Institute for Statistics and Economic Studies). In this way, we show that spatially channelling expected population growth before 2030 with the goal of increasing density could intensify urban centrality in the New Towns, leading to an increase in coherence (in terms of jobs-housing balance), a reduction in average commuting distances, a greater share of non-motorized transport, and transport network performance improvements. These effects are stronger in our targeted scenario than in the homogeneous case. Despite the challenges presented by population growth, it appears possible to maintain private transport modes' quality of service through changes in the structure of spatial interactions and transport requirements , in conjunction with planned road and transit development. Quality of service stabilization would require increased reliance on high-capacity urban trunk roads. In the targeted density scenario, traffic on the road network could even decrease in certain places, and capacity could then be reallocated to sustainable transport modes. Demographic change and transport quality of service can work together to both enhance secondary centres (improving accessibility through nearness) and increase the number of inhabitants capable of reaching a destination in a given amount of time, or the number of jobs accessible from residential areas.