All modes of freight transportation, combined, generated 4.3 trillion domestic ton-miles in 2001, 20 percent more than in 1991 (box 2-B). This represents an average growth rate of 1.8 percent per year during the period.
Domestic ton-miles for all modes, except water, grew during most of this period (figure 2-7). On an annual average basis, rail grew the fastest (4.4 percent), closely followed by air (3.8 percent) and truck (3.4 percent). Rail and truck accounted for the majority of domestic ton-miles at 37 percent and 29 percent, respectively, in 2001 (figure 2-8). Truck data, however, do not include retail and government shipments and some imports and, therefore, understate total truck traffic.
Water transportation and oil and gas pipelines1 accounted for 14 and 19 percent of domestic ton-miles, respectively, in 2001. Although domestic waterborne ton-miles decreased 27 percent between 1991 and 2001, waterborne vessels continued to play a prominent role in international trade . U.S. waterborne imports and exports, valued at $719 million, totaled 1.2 billion metric tons in 2001 . Oil and gas pipeline combined ton-miles grew 10 percent between 1991 and 1996, were stagnant in 1997, and then declined 7 percent through 2001.
Air freight declined between 2000 and 2001, from 15 billion ton-miles to 13 billion ton-miles. In addition to the impact of the terrorist attacks of September 11, 2001, and the economic downturn, some of the decline in air freight may be attributed to restrictions placed on the air transport of U.S. mail packages as a security precaution in late 2001. In general, air freight tends to transport high-value, relatively low-weight goods. Thus, on a ton-miles basis, air freight accounted for less than 1 percent of domestic freight in 2002, whereas on a value basis, this mode accounted for 7 percent of domestic freight .
1. U.S. Department of Transportation, Bureau of Transportation Statistics, U.S. International Trade and Freight Transportation Trends (Washington, DC: 2003).
2. U.S. Department of Transportation, Bureau of Transportation Statistics and U.S. Department of Commerce, U.S. Census Bureau, 2002 Economic Census, Transportation, 2002 Commodity Flow Survey (Washington, DC: 2003), preliminary data.
3. U.S. Department of Transportation, Maritime Administration, Office of Statistical and Economic Analysis, U.S. Foreign Waterborne Transportation Statistics, available at http://www.marad.dot.gov/statistics/usfwts/index.html, as of October 2003.
1 Pipeline ton-miles data in the previous October 2003 edition of Transportation Statistics Annual Report only included oil pipelines.