Sustainability is a powerful and relevant concept for managing the cities of the world as we move rapidly to an urbanised global economy. The integration of transport and land use to improve sustainable city development is critical. Sustainable transport is not just case of developing better technology; we must also develop ways of overcoming car dependence. This is explained in the terms of the Marchetti constant on travel time budgets and the average speed of modes in cities. Data are presented that show the constaints of the Marchetti budget. They suggest that car dependence is land use-induced in much of Australian, New Zealand and Amerian cities and is traffic-induced in the rapidly motorising cities of Asia. With few options for sustainable transport modes if Marchetti budgest are to be maintained, the main planning agenda for such cities in the 21st century is to reduce automobile dependence through better infrastructure and urban desegn. Sustainable transport wil require ways of accommodating car ownership but not car dependence. It will need real options for people to choose sustainable modes for most actvities and to have cars as alternatives. There are numerous policy challenges facing New Zealand to improve transport and land use planning, including better integrated decision-making between the Resource Management Act, Local Government Act and Land Transport Management Act. Professional advice and political leadership on how to advance sustainability will need constant improvement as the modernist assumptions of automobile dependence are not able to adequately answer the demands of a sophisticated public looking for better and more sustainable options.