Source: An, F., and A. Sauer. 2004. Comparison of Passenger Vehicle Fuel Economy and GHG Emission Standards Around the World. Pew Center on Global Climate Change, Washington, DC; Updated data obtained from “Global passenger vehicle standards,” The International Council for Clean Transportation, Retrieved from here , June 2012.
In the United States and worldwide, vehicle standards have been the main mechanism for improving vehicle efficiency and reducing emissions of conventional air pollution and greenhouse gases from the transportation sector. Increasing vehicle fuel-economy standards have had the effect of lowering greenhouse gas (GHG) emissions from what they otherwise would have been, because GHG emissions are closely related to fuel use.
Vehicle fuel economy standards can be expressed in miles per gallon (mpg) or kilometers per liter (km/l). Vehicle fuel economy can be improved by increasing energy efficiency of the drivetrain (engine and transmission) and by decreasing the amount of energy needed to move the vehicle (through reducing weight, aerodynamic drag, and rolling resistance). Countries with fuel economy standards include Australia, Canada, China, Japan, South Korea, and the United States.
Some vehicle GHG emission standards limit the tailpipe emissions from a vehicle, as well as from air conditioning, and are typically expressed as grams of CO2-equivalent per kilometer (gCO2e/km) while other standards only include CO2 in the measurement. The European Union uses a standard in gCO2/km while the United States uses a gCO2e/mi standard alongside the Corporate Average Fuel Economy (CAFE) program.
This graph is an update of our 2004 report  that takes into account the new U.S. vehicle fuel economy standards (see here  for more information). For this graph, the CO2 per kilometer standard in the EU and the other standards that are not measured in fleet average miles per gallon are converted to CAFE-equivalent miles per gallon values in order to establish an equivalent comparison. This conversion and adjustments are not straightforward since the form of the standards varies from country to country. For example, different countries cover different segments of the vehicle fleets, and use different procedures for determining compliance. For a description of the methodology for comparing the standards on a common basis, see here .