^a The Federal Aviation Administration has estimated vehicle-miles for general aviation aircraft through 1997, relying in part on hours-flown survey data. Vehicle-miles estimates for subsequent years are not yet available.

^b Includes vans, pickup trucks, sport utility vehicles, and other 2-axle, 4-tire motor vehicles that are not passenger cars.

^c Includes municipally owned transit and commercial, federal, and school buses.

^d Car-miles.

^e Includes light and heavy rail only.

^f Fiscal year data. Amtrak began operations in 1971.

^g Includes demand response, ferryboat, and other transit not specified; 1980 data include "other transit" only.

Key: N = data are nonexistent; P = preliminary.

Sources: Except as noted, various sources, as cited in U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics, National Transportation Statistics, table 1-32, available at http://www.bts.gov, as of October 2006.

2004 transit, commuter, and other transit: American Public Transportation Association, 2006 Public Transportation Fact Book, table 12 and 15, available at http://www.apta.com/research/stats/, as of October 2006.