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Vehicle-miles traveled (VMT)

30-year historical VMT by system

Traffic data definitions

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.


Vehicle type definitions

Cars, pickups, and vans All two-axle, four-tire vehicles that primarily carry passengers
Motorcycles All two- or three-wheeled motorized vehicles
Single unit two-axle All vehicles on a single frame, including trucks, camping and recreational vehicles, motor homes, etc., having two axles and dual-rear wheels
Single unit three-axle All vehicles on a single frame, including trucks, recreational vehicles, motor homes, etc., having three axles
Single unit four-axle All trucks on a single frame with four or more axles
Bus All vehicles manufactured as traditional passenger-carrying buses with two axles and six tires, or three or more axles
Combination four-axle All vehicles with four or less axles consisting of two units, one of which is a tractor or straight truck power unit
Combination five-axle All five-axle vehicles consisting of two units, one of which is a tractor or straight power unit
Combination six-axle All vehicles with six or more axles consisting of two units, one of which is a tractor or straight truck power unit
Double bottom All vehicles with six or more axles consisting of three units, one of which is a tractor or straight truck power unit