Freight Facts and Figures 2009
Table 3-10. Ton Miles of Truck Shipments by State: 2002
The measure of ton miles combines the weight and distance of freight movement to indicate how much overall demand freight is placing on the transportation system. This measure also demonstrates the dominant role of interstate commerce in freight movements for most states. Two-thirds of ton miles moved by truck are classified as interstate commerce. Almost 40 percent of ton miles moved by truck pass through a state between out-of-state origins and destinations. In the Midwest and many western states, a large majority of ton miles is considered through traffic, meaning that such traffic uses one state highway in order to serve shippers and consumers in other states.
Ton miles include domestic flows by truck, domestic portions of international trade by truck to and from ports, and domestic portions of international flows by truck to and from Canada and Mexico.
Technical Notes on Calculating Truck Shipments by State:
Ton miles for shipments by truck among places at least 50 miles apart are estimated by assigning flows in the Freight Analysis Framework (FAF) to the highway network as described in the report on Freight Traffic Analysis at www.ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports7/index.htm. Truck movements carrying international trade to and from maritime ports are counted as originating or terminating at the port, while truck movements across land borders are counted as originating or ending in Canada or Mexico. If the origins and destinations of international trade by truck through maritime ports were treated the same as by truck across land borders, ton miles for each state would remain the same, but the shares entering, leaving, within, and passing through coastal states would change slightly.
Local ton miles for shipments by truck among places less than 50 miles are estimated by multiplying the FAF tonnage originating in the state that was not assigned to the network by the ratio of ton miles to tons for shipments less than 50 miles in the 2002 Commodity Flow Survey. The ratio of ton miles to tons is the average distance traveled weighted by the weight of the shipments. The average for the United States was substituted for Minnesota, which has suppressed values in the 2002 Commodity Flow Survey. Local ton miles are counted with the state of origin. While some local traffic crosses state lines, the ton miles are very small and nationwide data to allocate that local traffic to flows entering and leaving each state are not available.
Except for truck moves of foreign trade to and from maritime ports, estimates of long-distance and local ton miles do not include truck portions of shipments using more than one mode. Inclusion of the truck portions of intermodal shipments would only increase national ton miles between one-half and two percent, depending on the trucking share of postal, parcel, and courier shipments. This estimated increase is based on the difference between total truck ton miles and truck-only ton miles plus the ton miles for postal, parcel, and courier shipments in the Commodity Flow Survey.1
1U.S. Department of Commerce, Census Bureau, 2002 Commodity Flow Survey, EC02TCF-US, December 2004, tables 1a and 2a.
Ton miles between places over 50 miles apart: U.S. Department of Transportation, Federal Highway Administration, Office of Freight Management and Operations, Freight Analysis Framework, version 2.3, August 2009.
Ton miles between places less than 50 miles apart (Local): Ibid., and U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statistics and U.S. Department of Commerce, Census Bureau, 2002 Commodity Flow Survey, July 2009.
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United States Department of Transportation - Federal Highway Administration