A number of U.S. state and local governments have adopted strategies for reducing greenhouse gas (GHG) emissions from transportation and land development. Although some have made significant progress in reducing GHG emissions from the power sector, transportation emissions in most states continue to rise. This Article details the range of existing and proposed state interventions to reduce transportation-sector GHG emissions, analyzes the trade offs of these strategies, and offers recommendations to improve and supplement such initiatives, including strategic use of planning mandates and funding and technical assistance. Additionally, regulating land use, shifting transportation spending, removing barriers to implementing road pricing policies, and altering standards for environmental impact analysis can more effectively reduce transportation-sector GHG emissions and mitigate climate change.