The use of energy-efficient technologies and renewable energy sources in transportation could reduce petroleum use and greenhouse gas emissions, but these approaches may face challenges in consumer adoption, infrastructure requirements, and resource constraints. The Transportation Energy Futures project of the U.S. Department of Energy reviewed opportunities for significant reductions in petroleum use and greenhouse gas emissions. On the basis of that review, a diverse set of strategies is explored: reduced energy intensity of transportation modes, lower use intensity of motorized transport, and reduced carbon or petroleum intensity through the use of electricity and hydrogen from renewable energy as well as the use of biofuels. Energy efficiency and demand-side approaches could stop the growth in total transportation energy. In the light-duty vehicle sector, growth in energy use already is projected to flatten; the deployment of technologies for energy efficiency could limit growth in the non-light-duty sector. Travel reduction and built environment changes could moderate personal transportation demand. Freight mass reductions and mode switching could slow or stabilize freight demand. Vehicles using electricity or hydrogen could enable access to renewable energy resources other than biomass. Challenges in fueling infrastructure expansion and market uptake of advanced vehicles are considered. Competition for biomass also is explored, considering markets for electricity, gasoline, diesel, jet fuel, and bunker fuel. The potential for the implementation of these strategies to displace U.S. petroleum use and reduce greenhouse gas emissions in the transportation sector is discussed along with the barriers to realizing this potential in the market.

This paper examines fuel economy and carbon standards for light vehicles (passenger cars and light trucks), discussing the rationale for standards, appropriate degrees of stringency and timing, regulatory structure, and ways to deal with "real world" fuel economy issues that may not be dealt with by the standards. There is no optimum method of establishing the stringency of a standard, but policymakers can be informed by analyses of technology cost-effectiveness from the viewpoint of different actors (e.g., society, vehicle purchasers) and of "top runners"—vehicles in the current fleet, or projections of future leading vehicles, that can serve as models for average vehicles some years later. The focus of the paper is on the US light vehicle fleet, with some discussion of applications to the European Union. A "leading edge" midsize car for the 2020 timeframe is identified, and various types of attribute-based standards are discussed. For the US, a 12–15 year target for new vehicle fleet improvement of 30–50% seems a reasonable starting point for negotiations. For 2030 or so, doubling current fuel economy is possible. In both cases, adjustments must be made in response to changing economic circumstances and government and societal priorities.

A key message of the Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change is that improved energy efficiency is one of society’s most important instruments for combating climate change. This article reviews a range of energy efficiency measures in the transportation sector as discussed in AR4 and assess their potentials for improving fuel efficiency. The primary focus is on light-duty vehicles because they represent the largest portion of world transport energy use and carbon dioxide emissions; freight trucks, a rapidly expanding source of greenhouse emissions, are also discussed. Increasing energy efficiency can be achieved by improving the design and technology used in new vehicles, but vehicle technology is only one component of fleet fuel economy. Measures that create strong incentives for customers to take energy efficiency into consideration when buying and operating their vehicles will be crucial to policy success.

Oil independence has been a goal of U.S. energy policy for the past 30 years, yet the term has never been rigorously defined. A rigorous, measurable definition is proposed: to reduce the costs of oil dependence to less than 1% of gross domestic product in the next 20 to 25 years, with 95% probability. A simulation model incorporating the possibility of oil supply disruptions and other sources of uncertainty is used to test whether two alternative energy policy strategies-business as usual (BAU) and an interpretation of the strategy proposed by the National Commission on Energy Policy (NCEP)-can achieve oil independence for the United States. BAU does not produce oil independence. The augmented NCEP strategy comes close to achieving oil independence for the U.S. economy within the next 20 to 25 years, but more effort is needed to achieve full independence. The success of the strategy appears to be robust regardless of how the Organization of the Petroleum Exporting Countries responds to it. Expected annual savings are estimated to exceed $250 billion per year by 2030.

Transport activity, a key component of economic development and human welfare, is increasing around the world as economies grow. For most policymakers, the most pressing problems associated with this increasing transport activity are traffic fatalities and injuries, congestion, air pollution and petroleum dependence. These problems are especially acute in the most rapidly growing economies of the developing world. Mitigating greenhouse gas (GHG) emissions can take its place among these other transport priorities by emphasizing synergies and co-benefits (high agreement, much evidence). Transport predominantly relies on a single fossil resource, petroleum that supplies 95% of the total energy used by world transport. In 2004, transport was responsible for 23% of world energy-related GHG emissions with about three quarters coming from road vehicles. Over the past decade, transport’s GHG emissions have increased at a faster rate than any other energy using sector (high agreement, much evidence). Transport activity will continue to increase in the future as economic growth fuels transport demand and the availability of transport drives development, by facilitating specialization and trade. The majority of the world’s population still does not have access to personal vehicles and many do not have access to any form of motorized transport. However, this situation is rapidly changing. Freight transport has been growing even more rapidly than passenger transport and is expected to continue to do so in the future. Urban freight movements are predominantly by truck, while international freight is dominated by ocean shipping. The modal distribution of intercity freight varies greatly across regions. For example, in the United States, all modes participate substantially, while in Europe, trucking has a higher market share (in tkm1), compared to rail (high agreement, much evidence). Transport activity is expected to grow robustly over the next several decades. Unless there is a major shift away from current patterns of energy use, world transport energy use is projected to increase at the rate of about 2% per year, with the highest rates of growth in the emerging economies, and total transport energy use and carbon emissions is projected to be about 80% higher than current levels by 2030 (medium agreement, medium evidence). There is an ongoing debate about whether the world is nearing a peak in conventional oil production that will require a significant and rapid transition to alternative energy resources. There is no shortage of alternative energy sources, including oil sands, shale oil, coal-to-liquids, biofuels, electricity and hydrogen. Among these alternatives, unconventional fossil carbon resources would produce less expensive fuels mostcompatible with the existing transport infrastructure, but lead to increased carbon emissions (medium agreement, medium evidence). In 2004, the transport sector produced 6.3 GtCO2 emissions (23% of world energy-related CO2 emissions) and its growth rate is highest among the end-user sectors. Road transport currently accounts for 74% of total transport CO2 emissions. The share of non-OECD countries is 36% now and will increase rapidly to 46% by 2030 if current trends continue (high agreement, much evidence). The transport sector also contributes small amounts of CH4 and N2O emissions from fuel combustion and F-gases (fluorinated gases) from vehicle air conditioning. CH4 emissions are between 0.1–0.3% of total transport GHG emissions, N2O between 2.0 and 2.8% (based on US, Japan and EU data only). Worldwide emissions of F-gases (CFC-12+HFC- 134a+HCFC-22) in 2003 were 0.3–0.6 GtCO2-eq, about 5–10% of total transport CO2 emissions (medium agreement, limited evidence). When assessing mitigation options it is important to consider their lifecycle GHG impacts. This is especially true for choices among alternative fuels but also applies to a lesser degree to the manufacturing processes and materials composition of advanced technologies. Electricity and hydrogen can offer the opportunity to ‘de-carbonise’ the transport energy system although the actual full cycle carbon reduction depends upon the way electricity and hydrogen are produced. Assessment of mitigation potential in the transport sector through the year 2030 is uncertain because the potential depends on: • World oil supply and its impact on fuel prices and the economic viability of alternative transport fuels; • R&D outcomes in several areas, especially biomass fuel production technology and its sustainability in massive scale, as well as battery longevity, cost and specific energy. Another problem for a credible assessment is the limited number and scope of available studies of mitigation potential and cost. Improving energy efficiency offers an excellent opportunity for transport GHG mitigation through 2030. Carbon emissions from ‘new’ light-duty road vehicles could be reduced by up to 50% by 2030 compared to currently produced models, assuming continued technological advances and strong policies to ensure that technologies are applied to increasing fuel economy rather than spent on increased horsepower and vehicle mass. Material substitution and advanced design could reduce the weight of light-duty vehicles by 20–30%. Since the TAR (Third Assessment Report), energy efficiency of road vehicles has improved by the market success of cleaner directinjection turbocharged (TDI) diesels and the continued market penetration of numerous incremental efficiency technologies. Hybrid vehicles have also played a role, though their market penetration is currently small. Reductions in drag coefficients of 20–50% seem achievable for heavy intercity trucks, with consequent reductions in fuel use of 10–20%. Hybrid technology is applicable to trucks and buses that operate in urban environments, and the diesel engine’s efficiency may be improved by 10% or more. Prospects for mitigation are strongly dependent on the advancement of transport technologies. There are also important opportunities to increase the operating efficiencies of transport vehicles. Road vehicle efficiency might be improved by 5–20% through strategies such as eco-driving styles, increased load factors, improved maintenance, in-vehicle technological aids, more efficient replacement tyres, reduced idling and better traffic management and route choice (medium agreement, medium evidence). The total mitigation potential in 2030 of the energy efficiency options applied to light duty vehicles would be around 0.7–0.8 GtCO2-eq in 2030 at costs

After decades of futile attempts to increase U.S. fuel economy standards for passenger cars, which have remained unchanged since enactment of the Corporate Average Fuel Economy (CAFE) Standards in Title V of the 1975 Energy Policy Conservation Act, it seems increasingly likely that new and tougher standards will be enacted in the near future - especially after the Senate's 21 June passage of energy efficiency bill H.R. 6. As this magazine went to press, the bill, which calls for a 40 percent increase in vehicle fuel economy by 2020 among other efficiency and alternative energy goals, was headed to the House of Representatives for more debate. Congress has seen proposals like this since the 1980s, but this is the first time that one of them has passed in the Senate. The Bush administration has also weighed in with a proposal to increase new vehicle fuel economy by 4 percent per year from 2011 to 2017, and the administrator of the National Highway Traffic Safety Administration (NHTSA) has asked Congress to grant the Secretary of Transportation the authority to restructure and increase CAFE standards for cars, a power denied by the original CAFE legislation. A confluence of events has led tomore » this change of political climate, including: the failure of world oil production and refining capacity to keep pace with rapidly growing demand, especially from China and other emerging economies, which has led to the highest oil prices since the 1980s and growing fears that world production of conventional oil may be close to its peak and rapid decline; the escalating influence of oil resources on geopolitics as China seeks to guarantee its future access to supplies, enhanced revenues from the higher prices, which prop up authoritarian regimes in Iran, Venezuela, Russia, and elsewhere and allow them increasing freedom of action; the enhancement of the role of climate change in political decision making by new reports from the Intergovernmental Panel on Climate Change (IPCC), with much strengthened language about the probability and severity of climate change and man's influence on it, and a recent Supreme Court decision rejecting the Environmental Protection Agency's assertion that it has no authority to regulate greenhouse gas emissions. New fuel economy standards will represent an ambitious and expensive undertaking on the part of the automobile industry and the nation, and proposals for new standards deserve careful congressional and public scrutiny.« less

Click to increase image sizeClick to decrease image size Additional informationNotes on contributorsSteven Plotkin Steven Plotkin is a Washington, DC-based energy and environmental analyst who currently specializes in analysis of transportation energy efficiency. He has worked extensively on automobile fuel economy technology and policy as a consultant to the U.S. Department of Energy and was a consultant to the National Research Council's recent study, Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards. For 17 years, he was a senior analyst and senior associate with the Energy Program of the Congressional Office of Technology Assessment (OTA), and prior to that, he was an environmental engineer with the U.S. Environmental Protection Agency. While at OTA, he was the project director and principal investigator for 11 OTA assessments of transportation energy conservation policy and technology and U.S. oil and gas resources, and he directed the environmental analysis on a number of other OTA assessments. Plotkin was a member of the National Research Council Committee on Undiscovered Oil and Gas Resources and currently is a consultnt to the National Highway Traffic Safety Administration on CAFE Reform. He is a member of the Transportation Research Board and the Society of Automotive Engineering. The author wishes to thank Danilo Santini of Argonne National Laboratory. Marc Ross of the University of Michigan, K. G. Duleep of Energy and Environmental Analysis, Inc., and John German of American Honda for their thoughtful reviews of a draft version of this paper. The author takes full responsibility for the contents of this paper.

The authors, who all took part in a discussion series relating to global climate change and transportation, discuss and summarize their impressions of the discussion series. Topics covered include greenhouse gas emissions, climate change, global warming, the science of global warming, vehicle and fuel technology, non-highway/transit modes of transportation, the impact of global warming, planning for sustainability, petroleum demand, fuel consumption, Kyoto Protocol, the difficulty (and possibility) of change, motor fuel prices, low emission vehicles, policy, and the responsibility of individuals and organizations.

This report presents the results of the first phase of Argonne National Laboratory's (ANL's) examination of the costs and energy impacts of light-duty hybrid electric vehicles (HEVs). We call this research an HEV Technology Assessment, or HEVTA. HEVs are vehicles with drivetrains that combine electric drive components (electric motor, electricity storage) with a refuelable power plant (e.g., an internal combustion engine). The use of hybrid drivetrains is widely considered a key technology strategy in improving automotive fuel efficiency. Two hybrid vehicles--Toyota's Prius and Honda's Insight--have been introduced into the U.S. market, and all three auto industry participants in the Partnership for a New Generation of Vehicles (PNGV) have selected hybrid drivetrains for their prototype vehicles.

This paper explores how advanced transportation technologies and alternative fuels, together with policies aimed at reducing greenhouse emissions and energy use, can help address the energy challenges facing the US transportation system over the coming decades. Three scenarios of future transportation energy use are constructed to represent alternative views of the urgency with which the federal government and the American people will view these challenges, and the policy interventions they will seek. The analysis concludes, first, that US transportation energy use and greenhouse emissions will increase virtually unchecked without policy intervention or unforeseen large, long-lasting fuel price increases, and second, that policies that stimulate technology development and deployment can substantially slow this growth—though not without a considerable time lag due to the slow turnover of the vehicle fleet and limits on the rate of technology development and deployment.

The transportation sector produces slightly more than 30% of the greenhouse gas emissions from the United States, with light-duty vehicles-automobiles and light trucks-accounting for more than half of the sector's emissions.(2) This makes the light-duty vehicle fleet an appealing target for carbon emissions reductions undertaken in pursuit of satisfying the United States' potential obligations under the Kyoto protocol. Furthermore, the current Light-duty vehicle fleet is essentially fully dependent on petroleum for its energy supply, so reductions in greenhouse gases will yield similar reductions in U.S. oil use, an attractive proposition to those concerned about U.S. dependence on petroleum imports.Reducing light-duty greenhouse gas emissions and petroleum use can be accomplished by increasing vehicle energy efficiency, shifting travel to more efficient modes, reducing travel overall (by increasing the price of travel, changing development patterns, or other means), changing fuels, and increasing vehicle occupancy. This article focuses on policies and technologies for increasing vehicle energy efficiency, though policies that raise fuel prices will encourage other physical measures, as well.

This paper addresses the relative fuel economy and emissions behavior, both measured and modeled, of technically comparable, contemporary hybrid and conventional vehicles fueled by gasoline, in terms of different driving cycles. Criteria pollutants (hydrocarbons, carbon monoxide, and nitrogen oxides) are discussed, and the potential emissions benefits of designing hybrids for grid connection are briefly considered. In 1997, Toyota estimated that their grid-independent hybrid vehicle would obtain twice the fuel economy of a comparable conventional vehicle on the Japan 10/15 mode driving cycle. This initial result, as well as the fuel economy level (66 mpg), made its way into the U.S. press. Criteria emissions amounting to one-tenth of Japanese standards were cited, and some have interpreted these results to suggest that the grid-independent hybrid can reduce criteria emissions in the U.S. more sharply than can a conventional gasoline vehicle. This paper shows that the potential of contemporary grid-independent hybrid vehicle technology for reducing emissions and fuel consumption under U.S. driving conditions is less than some have inferred. The importance (and difficulty) of doing test and model assessments with comparable driving cycles, comparable emissions control technology, and comparable performance capabilities is emphasized. Compared with comparable-technology conventional vehicles, grid-independent hybrids appear to have no clear criteria pollutant benefits (or disbenefits). (Such benefits are clearly possible with grid-connectable hybrids operating in zero emissions mode.) However, significant reductions in greenhouse gas emissions (i.e., fuel consumption) are possible with hybrid vehicles when they are used to best advantage.