NOTES: High-volume truck portions of the National Highway System carry more than 8,500 trucks per day, including freight-hauling long-distance trucks, freight-hauling local trucks, and other trucks with six or more tires. Uncongested segments have volume/service flow ratios between 0 and 0.75. Congested segments have reduced traffic speeds with volume/service flow ratios between 0.75 and 0.95. Highly congested segments are stop-and-go conditions with volume/service flow ratios greater than 0.95.
SOURCES: U.S. Department of Transportation, Federal Highway Administration, Office of Highway Policy Information, Highway Performance Monitoring System, and Office of Freight Management and Operations, Freight Analysis Framework, version 3.1, 2010.