"Table 1-2:  Number of Air Carriers, Railroads, Interstate Motor Carriers, Marine Vessel Operators, and Pipeline Operators",,,,,,,,,,,,,,,,
,1960,1965,1970,1975 ,1980 ,1985,1990  ,1995  ,1996  ,1997  ,1998  ,1999  ,2000  ,,,
Air carriersa,N,N,39,36,63,102,70,96,96,96,96,94,91,,,
Major air carriers,N,N,N,N,N,13,14,11,12,13,13,13,15,,,
Other air carriers,N,N,N,N,N,89,56,85,84,83,83,81,76,,,
Railroads,607,568,517,477,480,500,530,541,553,550,559,555,560,,,
Class I railroads,106,76,71,73,39,25,14,11,10,9,9,9,8,,,
Other railroads,501,492,446,404,441,f475,516,530,543,541,550,546,552,,,
Interstate motor carriersb,e,e,e,e,U,U,"216,000","346,000","379,000","417,000","477,486","517,297","560,393",,,
Marine vessel operatorsc,U,U,U,U,U,U,U,"2,519","2,505","2,494","2,534","R2,391",U,,,
Pipeline operatorsd,N,N,"1,123","1,682","2,243","2,204","2,212","2,378","2,338","2,282","2,225","2,216","2,163",,,
Hazardous liquid,N,N,N,N,N,f222,187,209,215,217,225,216,243,,,
Natural gas transmission,N,N,420,432,474,724,866,974,970,954,880,862,828,,,
Natural gas distribution,N,N,938,"g1,500","g1,932","1,485","1,382","1,444","1,397","1,363","1,366","1,382","1,351",,,
KEY:  N = data do not exist; U = data are not available; R = revised,,,,,,,,,,,,,,,,
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"a Carrier groups are categorized based on their annual operating revenues as major, national, large regional, and medium regional.  The thresholds were last adjusted July 1, 1999, and the threshold for major air carriers is currently $1 billion. The other air carrier category contains all national, large regional, and medium regional air carriers. ",,,,,,,,,,,,,,,,
"b Figures are for the fiscal year, October through September.  The Federal Motor Carrier Safety Administration deletes motor carriers from the Motor Carrier Management Information System (MCMIS) when they receive an official notice of a change in status.  This most often occurs when a safety audit or compliance review is attempted.  As a result, many inactive carriers are included in the MCMIS.  ",,,,,,,,,,,,,,,,
c The printed source materials do not contain totals for the number of operators and data files from which the figures can be determined are not available prior to 1993.,,,,,,,,,,,,,,,,
d There is some overlap among the operators for the pipeline modes so the total number of pipeline operators is lower than the sum for the three pipeline modes.,,,,,,,,,,,,,,,,
"e Prior to 1980, the source of motor carrier data was the Interstate Commerce Commission (ICC), which was abolished on Jan. 1, 1996.  (Certain functions were transferred to the Surface Transportation Board and the Department of Transportation.)  The system used by ICC to collect motor carrier data differs significantly from that used by the Federal Motor Carrier Safety Administration in its Motor Carrier Management Information System (MSMIS), which began operations in 1980. The MCMIS is updated weekly, but archive versions are not retained.  Because of differences between the two systems, data are not comparable and thus are not included here.",,,,,,,,,,,,,,,,
f This value is for 1986.  The number of hazardous liquid pipeline operators is not available for prior years.,,,,,,,,,,,,,,,,
"g Includes master meter and mobile home park natural gas distribution operators.  A master meter system is a pipeline system for distributing gas within, but not limited to, a definable area, such as a mobile home park, housing project, or apartment complex, where the operator purchases metered gas from an outside source for resale through a gas distribution pipeline system. The gas distribution pipeline system supplies the ultimate consumer who either purchases the gas directly through a meter or by other means, such as by rents. ",,,,,,,,,,,,,,,,
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SOURCES:  ,,,,,,,,,,,,,,,,
Air carriers:  ,,,,,,,,,,,,,,,,
"U.S. Department of Transportation, Bureau of Transportation Statistics, Office of Airline Information, Air Carrier Financial Statistics Quarterly (Washington, DC: Fourth quarter issues), ""Alphabetical List of Air Carriers by Carrier Group ..."".",,,,,,,,,,,,,,,,
Railroads:  ,,,,,,,,,,,,,,,,
"1960-1985: Association of American Railroads, Railroad Ten-Year Trends, Vol. 2 (Washington, DC), table I-2.",,,,,,,,,,,,,,,,
"1986: Ibid., Vol. 3 (Washington, DC), table I-2.",,,,,,,,,,,,,,,,
"1989-1998: Ibid., Vol. 16 (Washington, DC: 1999), p. 10.",,,,,,,,,,,,,,,,
"1999:  Ibid., Railroad Facts (Washington, DC: 2000), p. 3.",,,,,,,,,,,,,,,,
"2000: Ibid., Railroad Ten-Year Trends, Vol. 18 (Washington, DC), p. 9.",,,,,,,,,,,,,,,,
Interstate motor carriers:  ,,,,,,,,,,,,,,,,
"U.S. Department of Transportation, Federal Motor Carrier Safety Administration, Motor Carrier Management Information System (MCMIS) data, personal communication, Nov. 6, 2001.",,,,,,,,,,,,,,,,
Marine vessel operators:  ,,,,,,,,,,,,,,,,
"1995-97: U.S. Army, Corps of Engineers, Waterborne Transportation Lines of the United States, Volume 2, Vessel Company Summary(New Orleans, LA: Annual issues), source data files obtained by personal communication, Apr. 12, 2000.",,,,,,,,,,,,,,,,
"1998: Ibid., Internet site: http://www.wrsc.usace.army.mil/ndc/datavess.htm as of Apr. 10, 2000.",,,,,,,,,,,,,,,,
"1999: Ibid., Internet site: http://www.wrsc.usace.army.mil/ndc/datavess.htm as of Nov. 6, 2001.",,,,,,,,,,,,,,,,
Pipeline Operators:  ,,,,,,,,,,,,,,,,
"U.S. Department of Transportation, Office of Pipeline Safety, personal communication, Nov. 15, 2001.",,,,,,,,,,,,,,,,
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