Energy efficiency technologies for road vehicles Shigeki Kobayashi & Steven Plotkin & Suzana Kahn Ribeiro Received: 19 June 2008 /Accepted: 27 November 2008 / Published online: 6 January 2009 # Springer Science + Business Media B.V. 2008 Abstract 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 transpor- tation 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 oper- ating their vehicles will be crucial to policy success. Keywords Light-duty vehicles . Fuel economy. Fuel efficiency. Vehicle technologies . IPCC Introduction Transport activity, a key component of economic development and human welfare, is increasing around the world as economies grow. Transport activity will continue to increase in the future as economic growth fuels transport demand and the availability of trans- port drives development, by facilitating specialisation and trade. In 2004, transport energy use amounted to 26% of total world energy use and the transport sector was responsible for about 23% of world energy- related GHG emissions (IEA 2006a, b). The 1990��� 2002 growth rate of energy consumption in the transport sector was highest among all the end-use sectors. Road vehicles account for more than three- quarters of total transport energy use, with light- duty vehicles and freight trucks having the lion���s share (see Fig. 1, WBSCD 2004). Virtually all (95%) of transport energy comes from oil-based fuels, largely diesel (about 31% of total energy) and gasoline (47%). One consequence of this depen- dence, coupled with the only moderate differences in carbon content of the various oil-based fuels, is that the CO2 emissions from the different transport sub-sectors are approximately proportional to their energy use. Energy Efficiency (2009) 2:125���137 DOI 10.1007/s12053-008-9037-3 S. Kobayashi (*) Toyota Central R&D Laboratories., Inc., Nagakute, Aichi 480-1192, Japan e-mail: shige@mosk.tytlabs.co.jp S. Plotkin Argonne National Laboratory, Washington, DC, USA S. K. Ribeiro Federal University of Rio de Janeiro, Rio de Janeiro, Brazil

Transport activity is expected to grow robustly over the next several decades. A key driving force is the rapidly growing economies of the developing world, led by China and India, and the extraordi- nary growth in ownership of private vehicles in these areas. Also, energy-intensive intercity and international travel is growing rapidly and freight transport is expanding even faster than overall passenger travel. Unless there is a major shift away from current patterns of energy use, this expansion of travel activity will cause total trans- port energy use and carbon emissions to rise by about 80% above current levels by 2030 (WBSCD 2004). Improving energy efficiency offers an excellent opportunity for transport GHG mitigation through 2030. For example, average carbon emissions from new light-duty road vehicles could be reduced by up to 50% by 2030 assuming continued technological advances and strong policies to ensure that technol- ogies are applied to increasing fuel economy instead of increased power or other vehicle attributes (IPCC 2007). And low-carbon fuels, promotion of more efficient transport modes, and shifting urban design to allow excellent mobility with less travel and to better accommodate the more efficient modes can all play important roles in moving transport to a lower-carbon future. In this paper, we will try to assess the potential of various vehicle technologies for improving fuel efficiency, and also discuss briefly the additional cost of these technologies and the importance of on-road fuel efficiency. Trends in fuel efficiency During the past few decades, vehicle technologies have improved significantly and the efficiency of each drivetrain component has increased. As shown in Fig. 2, the outcome of these improvements was highly positive for new car fuel economy in the decade following the 1973 oil crisis, but in the 1980s, improvements in fleet fuel economy slowed and even reversed in Japan and the United States. What happened in these fleets is that the effect of steady improvements in the technical efficiency of the vehicles was counteracted by increased vehicle power, size and weight as manufacturers and vehicle purchasers traded off these characteristics against improved fuel economy (see Fig. 2). For example, the US Environmental Protection Agency (EPA 2008) has concluded that the fuel economy of the year 2004 fleet of cars and light trucks would have been 5.5 mpg (22%) higher had it remained at the same average weight and acceleration performance of the 1987 fleet. The rise of the market for light trucks played a significant role in the US stagnation in fuel economy between 1987 and the present. The SUV market share increased from less than 10% of the overall new light- duty vehicle market in 1990 to about 30% of vehicles built each year since 2003. The overall market share of light trucks increased to about 50%, with trucks averaging 5���7 mpg lower than cars. This trend was backed by low fuel prices in the future, higher fuel prices and stricter regulation should push fuel efficiency improvement. 0 2 4 6 8 10 12 14 16 18 75 80 85 90 95 2000 2005 France Germany Fuel Economy (km/L) US Truck JP US Car US Car+Truck Fig. 2 Sales-weighted fuel economy of new cars sold in US, Japan, France and Germany. Data source: EPA (2008) and EDMC (2007) Light Duty Vehicles 45% 2-wheelers 2% Freight trucks 25% Buses 6% Rail 2% Air 12% Shipping 10% Energy Use in Transport sector(2000) Fig. 1 World transport energy use in 2000, by mode (WBSCD 2004) 126 Energy Efficiency (2009) 2:125���137