Motor vehicles create approximately one-third of all carbon dioxide (CO2) emissions in the United States. Carbon dioxide emissions from burning of fossil fuels are a significant contributor to global warming and climate change. Each gallon of gasoline burned releases approximately 20 pounds of CO2, thus the quantity of CO2 emitted is directly related to the amount of fuel consumed. The lower the fuel economy (miles per gallon), the more CO2 is produced per mile driven. Motor vehicles are not equipped with emission control equipment that reduce CO2 emissions, and CO2 emissions from motor vehicles are not regulated under the Clean Air Act Amendments of 1990. At this time the only way to reduce CO2 emissions from a motor vehicle is to increase fuel efficiency.
Fuel economy standards (miles per gallon of gasoline, or "mpg") for motor vehicles are set by the US Department of Transportation and are called Corporate Average Fuel Economy (or "CAFE") Standards. Under current CAFE Standards, vehicles in the light-duty truck classification, which includes pick-up trucks, minivans, and sport utility vehicles (SUVs), must meet an average of 20.7 mpg, while passenger vehicles must average 27.5 mpg. The standards have not been changed since 1981. Between the mid-1970’s and mid-1980’s the average fuel economy increased fleet-wide as vehicle manufacturers produced, and consumers purchased, increasingly fuel-efficient vehicles in response to fuel shortages and increased costs of gasoline. Since peaking in 1987 at 22.1 mpg, however, the fleet-wide average fuel economy (including passenger vehicles and light- duty trucks) has steadily decreased, as manufacturers and consumers have tended toward larger, less-efficient trucks, SUVs, and minivans. In 2001, for the first time, light-duty trucks exceeded passenger vehicles in new car sales, and the average light vehicle fuel economy declined nearly 8 percent to 20.4 mpg, lower than it has been at any time since 1980.
For more data on transportation trends, visit the US Department of Energy Office of Transportation Web site and click on Fact of the week, or visit the Fact of the Week Archives.