Automobile use, fuel economy and CO2 emissions in industrialized countries: Encouraging trends through 2008?
Research Highlights
►Fuel economy of automobile fleets in industrialized countries has been improving since the late 1990s in Europe and since the early part of the 2000s in Japan and the US. Figures tabulated from national authorities reflect real on road consumption and distances driven. ►New vehicle test fuel economy has been improving, but technology has saved fuel faster, permitting ever larger and more powerful cars in the US and, until recently in Japan and Europe. Currently new vehicles in the US use about 24% more fuel/km in real traffic than in tests, those in Europe close to 20%, and those in Japan around 33%. ►The switch to diesel vehicles in Europe has only played a very small role in this improvement, as both diesel and gasoline vehicle fuel economy improved, with that of new gasoline vehicles improving slightly faster than that of new diesels. ►Car use per capita has stagnated in most industrialized countries, a consequence of higher fuel prices and possible other factors, such as road congestion, aging populations, and greater use of air travel.
Section snippets
Automobile fuel use and emissions: a gap in knowledge
Energy use and travel for personal transport in wealthy countries is dominated by automobiles. While fuel economy improvements and some slowing of the rise in ownership and use of automobiles has slowed the growth in fuel use, these vehicles still account for roughly 9% of total energy use (and 20% of oil use) in OECD countries, with higher shares in the United States (IEA, 2004). Their share in total energy use in developing countries is smaller, but rising rapidly (WBCSD, 2004, IEA, 2009).
Data and methods: focusing on the on-road fuel economy of entire fleets
The approach in this work follows the “ASIF” framework, in which fuel use depends on the product of total vehicle travel by vehicle fuel times the fuel intensity of that vehicle travel for each fuel. Adding CO2 emissions requires determining the CO2 content of each fuel used (Schipper et al., 2000). Apelbaum (2009) provides perhaps the most comprehensive review of how information on vehicle stocks, usage, and fuel intensity from both surveys and other sources are assembled to give a good
Results for on-road fuel intensity of the entire fleet
This section focuses on on-road fleet fuel intensity, the quantity directly proportional to energy use and CO2 emissions. Fig. 1 shows on-road fuel intensity of entire light-duty passenger fleets for a wide variety of developed countries from the early 1970s through 2007 or 2008.
Fuel intensity declined rapidly in the US in the 1970s and 1980s, while European countries experienced slower and less dramatic declines. Japan actually experienced an upturn in fuel intensity in the late 1980s and
Fuel economy of each year’s new vehicles
New car fuel economy, as measured by tests and weighted by sales, is an important indicator of how on-road fuel economy will behave as the fleet is renewed. The greater the difference (on road) between the fuel economy of new cars sold and those in the stock, and the more rapidly the stock turns over, the more rapidly the on-road fuel economy of the fleet will change.
A cautionary note: there is no simple way to compare new vehicle fuel intensities from tests among countries, both because test
The race for weight and power
Throughout this report we have avoided using the term “efficiency” for the indicators we have presented. The reason is clear—real fuel efficiency, if expressed as energy required to move a given mass a given distance, or the energy required to provide a given level of power to an engine, or to extract a given amount of power from a given volume has risen markedly in the US and Europe. Based on US and EU data (Environmental Protection Agency (EPA), 2010a, European Commission, 2010), Fig. 4, Fig.
Impact of diesels—disappointing?
Shifting from gasoline to diesel should save fuel and reduce CO2 emissions as well, goes the mantra in Brussels. In technical terms diesels are much more efficient than their gasoline counterparts of similar output (Schipper et al., 2002, Schipper and Fulton., 2009). In matched pairs, the diesel version of an automobile is somewhat heavier than the gasoline version, and has greater power to give roughly the same performance. Yet, because of the intrinsically higher efficiency of a diesel
Driving forces
The foregoing suggests that while improvements in on-road automobile fuel economy are critical for reducing oil demand and GHG emissions, serious oil saving or reduction in GHG emissions – say, bringing automobiles back to their 1990 levels of emissions or fuel use – cannot occur without both reductions in vehicle use and an end to the upward spiral of weight and power as well as improved fuel economy. The data on new vehicle properties and the diesel comparison show that between auto producers
A plateau in vehicle use—the other part of the equation
It was noted that in the “ASIF” approach (Schipper et al., 2000), fuel use or emissions depends on the product of car use (in kilometers/year) and fuel economy or emissions per kilometer. Will car use grow continually with higher incomes? Fig. 10 shows a novel portrayal of vkt/capita over time. The horizontal axis is per capita GDP over time, converted to real 2000 US dollars from real 2000 local currency at purchasing power parity. The vertical axis shows vkt/capita over time for cars. Data
Changing the trends?
Johansson and Schipper’s (1997) and Basso and Oum’s (2007) findings suggest economic forces – fuel prices – are an important determinant of fuel use for cars. In the US, at least, recent work suggests the reaction to higher prices would be small in the short term (Small and van Dender, 2007, Hughes et al., 2008, Hymel et al., 2010). Yet the plateau of vkt/capita or even vkt relative to income in so many countries suggests a larger reaction, particularly as fuel prices have risen slowly but
Conclusions
On-road fuel economy started improving in Japan and Europe by 2000, but hardly at all in the US from the early 1990s until 2003. New-vehicle test fuel economy has improved in all regions in recent years. Improvements in Europe through 2008 fell short of the target expressed in test CO2 emissions but landed about 5% above that figure in 2009. The shift to diesel cars was expected to “spark” significant fuel economy improvements in Europe to meet this target. But for a variety of reasons, new
Acknowledgment
The original version was written at the University of California Transportation Center, where the author was a visiting Scholar. This version of the paper was written with the support of EMBARQ, the WRI Center for Sustainable Transport, and its global strategic partners, the Shell Foundation and the Caterpillar Foundation. The author also acknowledges support of the Precourt Energy Efficiency Center, Stanford University.
Maria Mendiluce of the University of Madrid and Jennifer Carol Place of
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