($ millions)
| 1999 | 2000 | 2001 | 2002 | 2003 | |
|---|---|---|---|---|---|
| Truck | 29,296 | 36,008 | 34,697 | 35,094 | 35,935 |
| Rail | 293 | 1,433 | 1,575 | 2,051 | 2,473 |
| Pipeline | 135 | 206 | 99 | 100 | 85 |
| Other and unknown | 2,170 | 1,729 | 1,560 | 1,205 | 711 |
| Total | 31,894 | 39,376 | 37,931 | 38,450 | 39,204 |
SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics, Transborder Surface Freight Data, 1999-2003.