a2b07205_SCAN_Glossary_Traffic_Data_Definitions_Definition
[Data Type] Long Volume [Abbr.] LongVol [Definition] 
Number of large vehicles (such as eighteen wheel trucks) that were detected passing through a traffic zone. This value is only available in a side-fired configuration. A Side-fired configuration can only be configured to support Long Volume or Average Headway, but not both.
SCAN Glossary