This study explores how speed limit regulations for cars in Île-de-France affect air pollution from road trac and the economic costs linked to the population's exposure to this pollution. Using an enhanced version ofthe comprehensive and integrative modeling system, METRO-TRACE (Le Frioux, de Palma, and Blond, 2023), the research combines detailed geographical data, a mobility model to simulate population movements, and an air quality model to assess the economics costs associated with population exposure to road trac related air pollution . The ndings show that the yearly cost of population exposure to road trac pollution is 118.6 e per person. Implementing speed limit policies may not signicantly reduce these costs unless they are substained over the long term or accompanied by behavioral adjustments. The study highlights the intricate relationship between speed limits, pollutant emissions, and their economic consequences.