(Commodity Flow Survey Data Only)
NOTE: Shipments are grouped into distance categories based on Great Circle
Distance (GCD). GCD is the shortest distance between 2 points on the surface of a sphere.
Ton-miles estimates are based on estimated distances traveled along a modeled transportation network.
SOURCE: U.S. Department of Transportation, Bureau of Transportation Statistics, based on the 1993, 1997, and preliminary 2002 Commodity Flow Survey data.