This paper investigates the impact of urban form on household fuel consumption and car emissions in France. We in particular analyze three features of cities commonly referred to as the "3 D's" (Cervero & Kockelman 1997): Density, Design and Diversity. Individual data allow us to identify the effects of urban form and the spatial sorting of households on emissions. We also use instrumental variables to control for other endogeneity issues. Our results suggest that, by choosing to live at the fringe of a metropolitan area instead of the city center, a representative household would consume approximately six extra tanks of fuel per year. More generally, doubling residential Density would result in an annual saving of approximately two tanks per household. However, larger gains would result from better urban Design (job-housing central-ization, improved rail/bus routes to central business districts, reduced pressure for road construction and a less fragmented built environment in urban areas) while improved Diversity (the concentration of various local amenities such as shops and public facilities) can also help lower fuel consumption. Another important finding is that the relationship between the metropolitan population and car emissions in France is bell-shaped, contrary to that in the US, suggesting that small cities do compensate for their lack of Density/Diversity by environmentally-friendly Design.