The latest available data on hazardous materials shipments by mode in the U.S. were collected as part of the 1997 Commodity Flow Survey (CFS). Data from the 2002 CFS, conducted in partnership by BTS and the U.S. Census Bureau, will be released in late 2004.
U.S. Department of Transportation defines hazardous materials as belonging to one of nine hazard classes:
Respondents to the 1997 Commodity Flow Survey (CFS) provided a four-digit United Nations (UN) or North American (NA) identification number to help identify the shipment as hazardous material, and allow BTS to assign the shipment to one of the nine hazardous materials classes and their divisions and make summary tabulations.
Please note that because of the industry coverage and shipment definitions of the CFS, certain hazardous materials such as infectious substances or radioactive wastes were not well represented in the CFS data.