Box 2-1 - The Commodity Flow Survey and Supplementary Freight Data

Most of the national estimates of freight movement presented in this report are based on preliminary results from the 1997 Commodity Flow Survey (CFS), conducted by the Bureau of Transportation Statistics (BTS) and the Census Bureau, and additional estimates of freight shipments that are not fully measured in the CFS. Conducted for the first time in 1993 and again in 1997, the CFS is the nation's primary and most comprehensive data source on domestic freight movement. It surveys a sample of shipments by domestic establishments engaged in manufacturing, mining, wholesale trade, retail trade, and some selected services. The CFS collects information about what modes these establishments used to ship their products and materials, the types of commodities they shipped, and the value, weight, distance, origin, and destination of the shipments. The survey collects information on freight moved by each mode of transportation, and on freight moved by intermodal combinations (e.g., truck and train).

Although the CFS is the most comprehensive source of data on the domestic movement of goods and materials, some industries and commodities and most domestic movement of imports are not included. Thus, BTS has sought to fill in some of the missing pieces, such as crude petroleum pipeline shipments, some waterborne freight, and out-of-scope imports by surface, air, and water, in both the 1997 and 1993 estimates of commodity flows. This supplementary data can be used to compare the magnitude of overall national freight shipments in 1993 and 1997, but not to estimate specific commodities, sizes, or average length of haul.

Even with supplementary data, the existing data do not cover all freight movement on the nation's transportation network. Data on shipments by establishments included in the Standard Industrial Classification under farms, forestry, fishing, governments, construction, transportation, and most retail and service industries, municipal solid waste, and household movers are not available.

The completeness of estimates is due to revisions in the supplementary data to reflect refinements in methodology to include previously unavailable import data, and to address changes in the CFS coverage. Most of the 1993 data presented in this report are revised and differ from previous estimates for 1993 published by BTS and the Census Bureau. The Census Bureau revised some 1993 figures to make them directly comparable to the 1997 CFS results and BTS revised its supplementary data to improve its estimates. The revised data are noted where appropriate. The Oak Ridge National Laboratory (ORNL) prepared estimates for BTSof the value, tons, and ton-miles of crude petroleum and petroleum products shipments by pipelines and some waterborne shipments not captured in the CFS. ORNL converted Federal Energy Regulatory Commission (FERC) information on barrels of petroleum and petroleum products transported into tons and ton-miles. Estimates of value, tons, and ton-miles of waterborne shipments not captured in the CFS are based on information from the U.S. Army Corps of Engineers and the Department of Commerce's International Trade Division.