Functional classification is the process of grouping streets and highways according to the character of travel service they provide. This classification system recognizes that travel involves movement through a hierarchical system of facilities that progress from lower classifications handling short, locally-oriented trips to higher classifications that serve longer-distance travel at a higher level of mobility. The function performed by a roadway within this hierarchical system determines its classification.
Functional classification is an important transportation planning tool used for such programs as: Federal-aid funding and eligibility; traffic modeling; reporting of highway statistics; highway and pavement design; and measurement of highway system performance.
All public roadways, including those maintained by non-state agencies, are assigned one of the following functional classifications. A roadway's classification is further designated as urban or rural based upon whether or not it is located within one of the FHWA Adjusted Urban Area Boundaries.
- Roadways that comprise the Dwight D. Eisenhower National System of Interstate and Defense Highways and other Interstates as designated by the Secretary of Transportation
- Other Freeways & Expressways
- Non-Interstate roadways with access points limited to on-ramp and off-ramp locations and directional travel lanes usually separated by a physical barrier
- Other Principal Arterials
- Roadways that provide a high level of traffic mobility for substantial statewide travel and/or serve major activity centers and the longest trip demands within urban areas
- Minor Arterials
- Roadways that serve trips of moderate length to smaller geographic areas and at a slightly lower level of traffic mobility than Principal Arterials
- Major Collectors
- Roadways that distribute and channel trips between the lower classifications and the arterial systems
- Minor Collectors
- Roadways that distribute and channel trips between Local Roads and the higher classifications at a lower level of traffic mobility than Major Collectors
- Local Roads
- Roadways that primarily provide direct access to adjacent land and are not intended for use in long distance travel
The Federal Highway Administration (FHWA) establishes classification criteria and procedures but relies on state and local transportation planning professionals to assign the classifications. Further guidance is accessible from FHWA's Highway Functional Classification Concepts, Criteria and Procedures.
Functional Classification Resources