It is not intended to model or quantify the impacts of each policy option over time but instead to examine the means by which each influences behavior and the demand for and supply of energy- and emissions-saving technology, particularly in the modes of transportation with the greatest effect on the sector's consumption of petroleum and emissions of GHGs. In choosing among policies, elected officials must take into account many factors that could not be examined in this study, such as the full range of safety, economic, and environmental implications of their choices; therefore, the report does not recommend a specific suite of policies to pursue. Instead, the emphasis is on assessing each policy approach with regard to its applicability across transportation modes and its ability to affect the total amount of energy-intensive transportation activity, the efficiency of transportation vehicles, and GHG emissions characteristics of the sector's energy supply.