A study of 32 major world cities shows that there are very clear relationships between transport and urban form. Economic factors such as income and petrol price are less important than the direct policy instruments of the transport planner and urban planner, such as the relative provision of infrastructure for automobiles and rapid transit, or the density of population and jobs. Transport and urban planning policies are developed with quantitative guidelines that can help cities ease their dependence on the automobile, for example, by increasing population densities where these are under 30 per hectare
