NOTE: Total passenger-miles of travel (pmt) excludes motorcycle pmt and results in some double counting of bus pmt.
SOURCES: Passenger-miles—U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics 2002, table 1-34 revised, available at http://www.bts.gov/, as of October 2003. GDP—Based on chained 2000 dollar data from U.S. Department of Commerce (USDOC), Bureau of Economic Analysis, National Income and Product Accounts, summary GDP table, available at http://www.bea.doc.gov/bea/dn1.htm, as of January 2004. Population—USDOC, U.S. Census Bureau, National Intercensal Estimates 1990–2000 and National Population Estimates, available at http://eire.census.gov/popest/estimates.php, as of October 2003.