FIGURE 1-1 Trends in actual and projected U.S. transportation fuel use, 1995-2035. SOURCE: EIA (2010); Newell (2010).

biofuels) for transportation goes from about 13.5 million bbl/day in 2009 to 16.38 million bbl/day in 2035. Although the dependence on petroleum imports in these forecasts is somewhat ameliorated compared to recent trends, significant import dependence remains.

Added to the concern over high-priced oil and energy security is the concern regarding global warming. Nations around the world are beginning to exert more stringent control over human-made emissions, especially greenhouse gases (GHGs) such as carbon dioxide (CO2). Numerous discussions have taken place in Congress about climate change, and many pieces of climate change legislation have been proposed. The consumption of petroleum in the U.S. transportation sector accounted for about 1.81 billion metric tons of CO2-equivalent (CO2-eq) emissions in 2009, about 33 percent of total U.S. CO2-eq emissions from the burning of fuels. EIA (2010) forecasts that CO2-eq emissions from petroleum in the transportation sector in 2035 will be about 2.065 billion metric tons, about 33 percent of the projected U.S. total emissions of 6.32 billion metric tons of CO2-eq emissions from the burning of fuels. The EPA estimates that medium- and heavy-duty trucks and buses accounted for about 22 percent of CO2-eq emissions from the transportation sector in 2008 (EPA, 2010). Consequently, the transportation sector and the significant portion of that sector that is composed of MHDVs are important to any policies that are aimed at reducing greenhouse gas emissions. Thus, for the foreseeable future, there will be pressure to control and reduce greenhouse gas emissions. One approach to addressing such emissions is to use fuel more efficiently; another is to use fuels that emit less CO2 than petroleum-based fuels do.

Both the limited availability of oil and the additional pressures to reduce CO2 emissions will have a profound impact on automotive vehicles worldwide. In addition, as briefly discussed in the next section, the United States is implementing policies on fuel economy that will directly impact the vehicle sector. These forces will pressure vehicle manufacturers to make renewed efforts to reduce both fuel consumption and exhaust emissions. Light-duty vehicle manufacturers have already made significant improvements in reducing fuel consumption and even more progress in reducing vehicle emissions. Emissions of oxides of nitrogen (NOx) and particulate matter (PM) from heavy-duty vehicles have been significantly reduced by PM regulations that went into effect in 2007 and NOx regulations that were phased in between 2007 and 2010. However, reductions in fuel consumption of the large commercial truck fleet have not been as impressive, partly because of the growth in the number of miles driven by large trucks during the past decade (NRC, 2008; NAS-NAE-NRC, 2009a).

Thus, with regard to economic considerations, energy security, and environmental reasons, the transportation sector is a key area for consideration and policy focus, and the medium- and heavy-duty vehicle component significant. The 21CTP can play an important role is this regard.


The economic and policy environment outside the DOE continues to change, and various external initiatives and policies can affect the DOE and specifically the Partnership: such developments that may affect the Partnership have continued to emerge since the publication of the NRC Phase 1 report (NRC, 2008). The control of emissions from the engines of heavy-duty trucks with gross vehicle weight (GVW) over 8,500 pounds (lb) began in 1973 in California and in 1974 in the United States as a whole. The federal standards were harmonized with California standards beginning with model year (MY) 2004, and stringent emissions standards for heavy-duty diesel engines came into effect, as noted in the previous section, in the 2007-2010 time period. These increasingly stringent engine emissions standards were an important driver for R&D for engine, emissions control, and fuels.5 Reaching low emissions of hydrocarbons (HCs), carbon monoxide (CO), NOx, and PM in terms of grams per brake horsepower-hour (g/bhp-h) was a significant challenge if fuel consumption was constrained to not increase. The changes in U.S. emission standards over time are presented in Figure 1-2 (DOE, 2010c, d).

With the increasing concern in Congress and the administration about energy security and greenhouse gas emissions, numerous actions are taking place that will create incentives for technology development for vehicles as well as improve the operational efficiency of managing the movement of freight in the United States (e.g., through driver education, longer combination vehicles, reducing congestion, etc.). Although the National Highway Traffic Safety Administration (NHTSA) has regulatory authority over fuel economy standards for vehicles, the EPA has the authority to regulate CO2 and other greenhouse gases as air pollutants under the Clean Air Act, thus empowering the EPA to regulate vehicle


5 A summary review of these emissions standards and changes can be found in the NRC Phase 1 report, Chapter 1 (NRC, 2008), as well as in references in this chapter (Ehlmann and Wolff, 2005; Johnson, 1988).

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