a Data before 2007 are for Passenger car and Other 2-axle, 4-tire vehicles, respectively.
bBefore 1995, light duty vehicle, short wheel base (previously Passenger car) fuel efficiency includes motorcycles.
Key: U = unavailable.
Notes: Fuel economy is miles divided by gallons. New vehicle data are for model years. Average fleet data for 2007 to 2009 were calculated using a new methodology developed by FHWA. Data for these years are based on new categories and are not comparable to previous years. The new category Light duty vehicle, short wheel base includes passenger cars, light trucks, vans and sport utility vehicles with a wheelbase (WB) equal to or less than 121 inches. The new category Light duty vehicle, long wheel base includes large passenger cars, vans, pickup trucks, and sport/utility vehicles with wheelbases (WB) larger than 121 inches.
Source: National Highway Traffic Safety Administration, Summary of Fuel Economy Performance (Washington, DC: Annual Issues), available at http://www.nhtsa.gov/ and Federal Highway Administration, Highway Statistics (Washington, DC: Annual Issues), table VM-1, available at http://www.fhwa.dot.gov/policyinformation/statistics.cfm as cited in U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, National Transportation Statistics, table 4-23, available at http://www.bts.gov/publications/national_transportation_statistics/ as of December 2011.