Why are US fossil fuel carbon emissions falling? Why are US oil imports falling? Why is US gasoline demand back to September 2001 and oil consumption at May 1999 levels? Rapidly rising fuel efficiency in new vehicles is one major reason for all the foregoing. Consider these numbers from a University of Michigan study:
New light duty vechicles (cars, pickup trucks, minivans, vans, and SUVs) on sale in 2012 average 21.5 mpg, compared to 21.2 mpg in 2011; 20.7 mpg in 2010; and 19 mpg in 2009. In short the fuel efficiency of vehicles on sale has improved by about 13% since 2008. http://ns.umich.edu/new/releases/20197-fuel-economy-of-new-vehicles-continues-to-rise-feb2012.
The vehicles actually bought by consumers were more fuel efficient than the average vehicle available for sale in every year since 2008, as consumers bought more higher fuel efficient vehicles. For example, vehicles bought in 2011 averaged 22.5 mpg; 22.1 in 2010; and 21.3 mpg in 2009; and 20.8 mpg in 2008.
Rising fuel efficiency in vehicles is cutting gasoline demand, pollution, and imports of foreign oil. It is one reason that even US carbon emissions have been declining.
The increasing fuel efficieny will certainly continue as federal law requires a fleet average of 34.1 mpg by 2016 and a proposed regulation would raise that further to 54.5 mpg by 2025.
Fuel efficiency and rising production of domestic oil and oil substitutes like biofuels, natural gas, and electricity are moving Uncle Sam to energy independence.