Truck Movements in America: Shipments From, To, Within, and Through States

Trucking is a vital segment of the transportation system in the United States. The Commodity Flow Survey estimates that trucks carried about $4.6 trillion worth of goods over 900 billion ton-miles in 1993. This report presents new estimates of the movements of commodities by truck to, from, within, and through each state. These estimates show the magnitude of interstate commerce on the nation's highways, particularly on the traffic that travels through states.

Figure 1 and Table 1 show the value of truck shipments and indicate the relative importance of trucking to each state. Figure 2 and Table 2 show the ton-miles of truck shipments and indicate the amount of trucking activity over the highways. Ton-miles of each interstate shipment are divided among the states in proportion to the distance along the route used by the shipment, while the value of the interstate shipment is counted in each state in which the shipment passes. Thus, individual state totals may be added across states for ton-miles, not for value.

Major patterns that emerge from the data include:

• Nationally, shipments crossing state boundaries accounted for 73 percent of the ton-miles and 55 percent of the value of commodity movements by truck. A small proportion of the shipments account for much of the ton-miles. Shipments of 1,000 miles or more account for 10 percent of the value, only 2 percent of the weight, and 25 percent of the ton-miles of shipments by truck.
• Interstate commerce accounted for at least half of trucking by value of shipments in all but three states. The same is true in terms of ton-miles.
• Shipments passing through states accounted for more than half of the value of commodity movements by truck in 25 states, and in 19 states, through shipments accounted for more than half of the state's ton-miles by truck.
• The largest shares of shipments within states tend to be in states that are geographically large with widely separated major cities, such as California and Texas, or in the corners of the country, such as Florida and Washington. The relatively large share of intrastate traffic in Michigan is overstated because imports from Canada are not included in the estimates.
• The large concentration of truck activity in the corridor from Illinois to Pennsylvania clearly shows that the nation's historic manufacturing belt remains vital.

The Bureau of Transportation Statistics (BTS) developed these estimates using the 1993 Commodity Flow Survey and the 1992 Census of Agriculture. The Bureau of the Census conducted the Commodity Flow Survey with guidance and financial assistance from BTS and the Federal Highway Administration. The survey asked a national sample of 200,000 shippers what they shipped, how the shipments were transported, and where the shipments went. The routes used by the shipments were estimated by Oak Ridge National Laboratory using sophisticated network simulation models and data on highways, railroads, waterways, pipelines, and air routes published by BTS in its National Transportation Atlas Database. The survey covered shippers in manufacturing, mining, and wholesale. BTS added estimates of farm-based shipments from the Census Bureau's 1992 Census of Agriculture. The resulting estimates include most truck activity, except imports, shipments between foreign countries that pass through the United States, and shipments by households, retail, service, and government establishments.

Estimates of truck activity presented in this report differ from statistics published by the Bureau of the Census. This is the first publication in which BTS accounted for farm-based shipments and incorporated all shipments in the network simulations. BTS also separated exports from domestic commodity flows, which shifted some "within state" shipments to "from state" shipments and some "to state" shipments to "through state" shipments in border states. The statistical reliability of these estimates are comparable to the reliability estimates published by the Bureau of the Census for the Commodity Flow Survey.

For more information on truck shipments from the Commodity Flow Survey, call Felix Ammah-Tagoe at 202-366-8926. For additional copies of this publication, call 202-366-3282, or send your name and address to orders@bts.gov.