Peak-Period Congestion on the National Highway System: 2012 Map
Highly congested segments are stop-and-go conditions with volume/service flow ratios greater than 0.95. Congested segment have reduced traffic speeds with volume/service flow ratios between 0.75 and .095. The volume/service flow ratio is estimated using the procedures outlined in the HPMS Field Manual Appendix N.
U.S. Department of Transportation, Federal Highway Administration, Office of Freight Management and Operations, Freight Analysis Framework, version 4.3. 2017.
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