This paper quantifies the potential reduction in US greenhouse gas emissions that could be achieved by using advanced-technology motor vehicles and low-emission bio-fuels. These two approaches are compared to a variety of other approaches to reduce transportation sector emissions. It is concluded that only strong fiscal measures can produce emission reductions as large as are available from advanced-technology vehicles and low-emission fuels. A technology strategy is offered that should make the benefits of these technologies likely to occur should the US enter into a binding agreement to limit US greenhouse gas emissions. Various policy scenarios that could result from such an agreement are presented with the result that the technology strategy to produce advanced-technology vehicles and bio-fuels remains the most viable and cost-effective approach to control the future growth of transportation-sector greenhouse gas emissions.