Sustainable Transportation Energy Pathways (STEPS)
Suggested Citation: Emil Frankel et al. (2011) Policy Options for Reducing Energy Use and Greenhouse Gas Emissions from U.S. Transportation. Transportation Research Board Special Report 307, Committee for a Study of Potential Energy Savings and Greenhouse Gas Reductions from Transportation, (Emil H. Frankel, Chair)
This report examines U.S. transportation’s consumption of petroleum fuels and the public interest in reducing this consumption to enhance national energy security and help control emissions of carbon dioxide (CO2) and other greenhouse gases (GHGs). Scientific analyses and models indicate a need to stabilize atmospheric concentrations of these gases by the middle of this century. Worldwide emissions reductions of up to 80 percent may be needed over the next four decades as a consequence. A response by the transportation sector to this energy and emissions challenge will be important, because the sector accounts for more than two-thirds of the petroleum consumed in the United States and produces between one-quarter and one-third of all the CO2 emissions attributable to the country’s energy consumption.
The report reviews policy options to bring about desired energy consumption and GHG emissions reductions from U.S. transportation over the next half century. 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. For each policy option, consideration is given to the challenges associated with implementation and with the production of large savings in energy and GHG emissions over a time span of decades.
Given the magnitude of the needed emissions reductions indicated by climate change science and GHG modeling, it is difficult to envision the U.S. transportation sector contributing meaningfully to these reductions without a close alignment of policies to induce and sustain the needed energy- and emissions-saving response. Gradual improvements in the energy efficiency of transportation vehicles and their operations over the past several decades—brought about in part by public policies—have helped temper transportation’s overall demand for carbon-rich petroleum, even as the total population, automobile ownership, personal travel, freight demand, and traffic congestion have grown. However, a mere tempering of the growth in petroleum demand by transportation will not yield deep reductions in the CO2 and other GHGs emitted from transportation over the next 40 years. In this respect, the policy challenge that lies ahead is more complex than the energy conservation challenge facing the nation over the past 40 years. The achievement of deep reductions in energy use and emissions by midcentury will require more than gradual improvements in vehicle energy efficiency. It is likely to require reducing the GHG impact of the transportation fuel supply and the total amount of energy- and emissions-intensive transportation activity.