Automobile use, fuel economy and CO2 emissions in industrialized countries: Encouraging trends through 2008?

Car use and fuel economy are factors that determine oil demand and carbon dioxide (CO2) emissions. Recent data on automobile utilization and fuel economy reveal surprising trends that point to changes in oil demand and CO2 emissions. New vehicle and on-road fleet fuel economy have risen in Europe and Japan since the mid 1990s, and in the US since 2003. Combined with a plateau in per capita vehicle use in all countries analyzed, these trends indicate that per capita fuel use and resultant tail-pipe CO2 emissions have stagnated or even declined.Fuel economy technology, while important, is not the only factor that explains changes in tested and on-road fuel economy, vehicle efficiency and transport emissions across countries. Vehicle size and performance choices by car producers and buyers, and driving distances have also played significant roles in total fuel consumption, and explain most of the differences among countries. Technology applied to new vehicles managed to drive down the fuel use per unit of horsepower or weight by 50%, yet most of the potential fuel savings were negated by overall increased power and weight, particularly in the US. Similarly, the promise of savings from dieselization of the fleet has revealed itself as a minor element of the overall improvement in new vehicle or on-road fuel economy. And the fact that diesels are driven so much more than gasoline cars, a difference that has increased since 1990, argues that those savings are minimal. This latter point is a reminder that car use, not just efficiency or fuel choice, is an important determinant of total fuel use and CO2 emissions.We speculate that if the upward spiral of car weight and power slows or even reverses (as has been observed in Europe and Japan) and the now mandatory standards in many countries have the intended effect that fuel use will remain flat or only grow weakly for some time. If real fuel prices of 2008, which rivaled their peaks of the early 1980s, fell back somewhat but still remain well above their early 2000 values. If the prices remain high, this, combined with the strengthened fuel economy standards, may finally lead to new patterns of car ownership, use and fuel economy. However, if fuel prices continue their own stagnation or even decline after the peaks of 2008 and car use starts upward, fuel use will increase again, albeit more slowly.

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.