There are many options available for reducing the fuel, energy, and GHG emissions impacts of LDVs. As our understanding of these options improves, our ability to better prioritize their usefulness in moving toward significantly reduced impacts increases. We should continue to adopt policies to reduce transportation energy demand and emissions, while using our evolving information base to assess and reassess which options have the greatest leverage. While recommendations like ours can never be “proven” and will always be subject to some disagreement, the sequence of topics we have analyzed here constitutes, in our judgment, a valid basis for identifying pathways that are likely to have the greatest benefit. Achieving our overall goal—reducing fleet fuel and energy consumption and GHGs by three-quarters or more—will be extremely challenging. All of us involved in studying the ways in which we can move toward that goal have a responsibility to provide ever more useful and focused advice.

—“On the Road Toward 2050”

The research for the report was done by a team of graduate students from 2009 to 2014, and includes some 20 projects. The report addresses topics related to the evolution of vehicle technology and its deployment, the development of alternative fuels and energy sources, the impacts of driver behavior, and the implications of all of these factors on future GHG emissions in the United States, Europe, China, and Japan.

In the United States, LDVs alone currently account for 43% of petroleum demand and 23% of GHG emissions, when fuel production is considered. The United States, Europe, China, and Japan consume over half of the world’s petroleum, making these countries particularly critical in efforts to reduce petroleum consumption and the associated emissions.

Overall, we have substantial opportunities for reducing environmental and climate impacts from light-duty road vehicles. Achieving reductions in vehicle-related greenhouse gas emissions will require a major global shift towards more efficient personal and freight vehicles—including those powered with alternative, low-carbon energy sources—along with a corresponding reduction in demand for energy-intensive vehicles that is strongly incentivized with supportive policies, and ongoing research towards the technology breakthroughs needed to achieve a transition to a truly low-carbon transportation system.

—John Heywood

The results of the report’s plausible yet aggressive scenarios for the United States show the potential for technological improvements to more than offset fleet growth and, by 2050, reduce fuel use and GHG impacts by up to 50%.

Average on-road fuel consumptions (tank to wheels) of the different propulsion systems in an average light-duty vehicle: 2010, 2030, and 2050. Includes vehicle weight reduction: at constant acceleration capability. Values normalized to standard naturally-aspirated gasoline engine vehicle. Note the factor-of-two reductions anticipated in this “realistic yet aggressive” scenario for each propulsion system, and the relative ranking of several promising propulsion systems in vehicles. Progress will be made by both steadily improving each propulsion system and by shifting increasing fractions of the sales mix each year to the more efficient alternatives. —“On the Road Toward 2050” Click to enlarge.

In Europe, the anticipated fleet growth is less, as are the potential reductions from technology improvements, but the overall percentage reduction potential is similar to that in the United States.

Evolving US new LDV market: percent sales by powertrain type out to 2050. Other major regions likely to have similar evolution: diesel in Europe currently about 50% of the ICE sales, but that fraction is slowly decreasing. Going beyond improvements in conventional technologies and conservation measures, a long-term transformation of the transportation energy system to one or more alternative fuels and energy sources is the ultimate piece of the puzzle of reducing petroleum consumption and GHG emissions. Today, it is possible to identify a number of potential alternative fuels, including electricity, hydrogen, biofuels, and natural gas. However, it is not yet clear that any one of these can fully assume the dominant position that petroleum has held as the preferred transportation energy source for the past century. More research, development, and demonstration studies are needed to lay the foundation for such a long-term transformation. —“On the Road Toward 2050” Click to enlarge.

In Japan, fleet size and use are declining, so the overall reduction in impacts could be larger. In China, though current growth in fleet size is large, reductions in that growth rate and substantial technology improvements over time are expected to level off fleet fuel consumption and GHG emissions by about 2040.

The report makes several recommendations that should be implemented to attain the 40-50% reductions in fleet fuel consumption and GHG emissions by 2050 that the overall assessment indicates are feasible in North America, Europe, and Japan.

Larger reductions on this time scale will need additional major efforts, and would likely require a significant reduction in travel demand, and more rapid development and substantial distribution and use of low-GHG-emitting alternative sources of transportation energy, such as electricity and hydrogen.

The recommendations include:

• Improving the fuel consumption of mainstream vehicles is the primary nearer-term opportunity for reducing fuel use and GHG emissions. Market-based incentives should be implemented to support the US Corporate Average Fuel Economy (CAFE) LDV requirements.

• The CAFE standard targets for LDVs leading up to the 2025 models need to be clarified as the often-quoted average number of 54.5 miles per gallon will not reflect what most new car buyers should expect to achieve in 2025.

• Vehicle electrification is a potentially promising alternative energy source and propulsion system technology to move toward lower fleet GHG emissions over time.

  From our studies of vehicle electrification, we have concluded that PHEVs offer the most viable path toward powering more vehicle miles with electricity. The market for pure BEVs is likely to be limited because their inherently limited driving range and long recharging times, and their high cost, make them less attractive to purchasers looking for an all-purpose vehicle. However, BEVs do appeal because their propulsion system is simpler than an ICE, and they do not dilute their “electric miles” with “gasoline miles,” as does a PHEV. However, the flexibility and lower costs of PHEVs appear to trump this simplicity, certainly in the nearer term. Planning for electrification should be based on growth in the PHEV market over time in contrast to the more limited expected growth in the BEV market. Recharging requirements for PHEVs are not the same as for BEVs: especially, the demand for “fast recharging” stations is really not there.

  —“On the Road Toward 2050”

• The need to improve mainstream fuels, and to enable a transition to alternative fuels is both obvious and remarkably challenging. Conventional hydrocarbon fuels should be improved in the near term while we continue to develop a portfolio that includes the more promising alternative fuel options, and refine strategies as we learn more about the costs, benefits, and the viability of the pathways of different fuels.

• The overall strategy should include conserving energy through changes in travel behavior, improving conventional technologies, and transforming the transportation system to increasingly use lower carbon energy sources.

• Policies should be implemented to enforce a carbon tax combined with an increasing fuel tax; current CAFE regulations should be extended and new regulations should be implemented; and improvements in existing fuels that would achieve fleet-wide GHG emissions reductions should be explored.

“On the Road toward 2050” is a synthesis of research conducted in the Sloan Automotive Laboratory at MIT over the past five years, primarily under the direction of Heywood, with support from the MIT Energy Initiative (MITEI) as well as MITEI Founding Member Eni S.p.A. It is the third report in a series that records the research findings of this group; “On the Road in 2020” was published in 2000 and “On the Road in 2035” was published in 2008.

Because MIT has other ongoing research programs in many domains vital to transportation and mobility, MITEI has recently organized a multi-disciplinary study team from across the Institute to examine how the complex interactions between engine technology options, fuel options, vehicle characteristics, refueling infrastructure, consumer choice, public transit options, new mobility business models, and government policy will shape the future landscape of mobility.

MITEI’s study on “Mobility of the Future” will explore these and other questions.

The MIT Energy Initiative is MIT’s hub for energy research, education, and outreach. Founded in 2006, MITEI’s mission is to create low- and no-carbon solutions that will efficiently meet global energy needs while minimizing environmental impacts and mitigating climate change.

BP, Chevron, Concawe, the Department of Energy U.S.-China Clean Energy Research Center’s Clean Vehicle Consortium, the MIT Joint Program on the Science and Policy of Global Change, and the MIT-Portugal Program also provided support for the report.