| Interstate | A full-controlled access divided facility of at least four lanes designated by the Federal Highway Administration as part of the Interstate Highway System |
| Municipal | Within the limits of any incorporated city or town |
| Municipal interstate | A full-controlled access divided facility of at least four lanes within the limits of any incorporated city or town |
| Municipal other primary | All federal and state highways, excluding interstates, within the limits of any incorporated city or town |
| Municipal streets | Any street within the limits of any incorporated city or town other than interstate or other primary highways |
| Other primary | All federal and state highways, excluding interstates |
| Road and city street | Nonprimary and noninterstate routes |
| Rural | Outside the limits of any incorporated city or town |
| Rural interstate | Full-controlled access divided facility of at least four lanes outside the limits of any incorporated city or town |
| Rural other primary | All federal and state highways, excluding interstates, outside the limits of any incorporated city or town |
| Rural secondary | Any nonfederal or state highway outside the limits of any incorporated city |
| Vehicle type | A series of motor vehicle types that have been grouped together because of their design similarities |
| VMT | A measure of total vehicle activity. For a given segment of roadway, the VMT is obtained by multiplying the annual average daily travel (AADT) by the length of the roadway segment. For example, on a 5-mile highway segment traveled by 5,000 vehicles daily (an average obtained over a year), the VMT would be 25,000. |
