Figure 1,,,,,,
Passenger-Miles of Travel,,,,,,
,,,,,,
Trillions,,,,,,

Year,1975,1980,1985,1990,1995,1999
,"2,557,177","2,871,260","3,202,200","3,800,500","4,131,300","4,621,392"

SOURCE:  1975–1995—various sources as cited in U.S. Department ,,,,,,
"of Transportation, Bureau of Transportation Statistics, National ",,,,,,
"Transportation Statistics 2000 (Washington, DC: 2001); 1999 ",,,,,,
data—various sources as compiled by the Bureau of Transportation ,,,,,,
Statistics.,,,,,,