Mitigating global climate change will require a profound transformation of energy use sectors throughout the world and this challenge is particularly acute for the United States transportation sector. Market forces alone are unlikely to change transportation-energy technologies and infrastructures sufficiently to address the needs for an environmentally sustainable system. A set of policies for encouraging technological advances and promoting sustainable planning, operations, and pricing of transportation services was analysed for its effects on sector energy use and greenhouse gas (GHG) emissions. Baseline projections show US transport sector GHG emissions increasing over the 1990 level 28% by 2010 and 58% by 2030. The combined impacts of the policies analysed would be substantial emission reductions that grow over time, with GHG emissions returned to the 1990 level by 2010 and cut to 35% lower by 2030. Due to fuel savings from technology-based efficiency improvements, it was found that the economic benefits accruing from these reductions would outpace costs almost from the outset.