Time is fast running out for formulating a viable global climate policy regime even as it seems obvious that the major initiative will have to come from the United States, which Currently appears indisposed to take any meaningful action at all. This paper reviews the prospects for emissions reductions in the US passenger transport sector and the technical, economic, social, and political barriers to developing policies that focus solely on technology or pricing. Using scenarios it shows that, in order to meet stringent emissions targets over the coming half-century, technology and pricing policies may have to be supplemented by strategies to change life-styles and land uses in ways that effectively reduce car dependence. In the medium to long term, bold initiatives that treat vehicle users as citizens capable of shifting their interests and behaviour could form kernels of social change that in turn provide opportunities for removing many of the social and political constraints. (c) 2004 Elsevier Ltd. All rights reserved.