All public roadways, including those maintained by non-state agencies, are assigned a functional classification regardless of the responsible agency. Following are the eight major functional classes which are described more fully below.
- Rural Principal Arterial
- Rural Minor Arterial
- Rural Collector Road
- Rural Local Road
- Urban Principal Arterial
- Urban Minor Arterial
- Urban Collector Street
- Urban Local Road
Rural Principal Arterial (Rural Inst, Rural PA):
Rural principal arterials comprise a system of continuous, connected, rural routes having trip length and density suitable for statewide or interstate travel. They provide for movement between all urban areas with a population of 50,000 or more and most urban areas with a population of at least 25,000. This classification has two sub-classifications:
- Interstates: Interstate routes located outside urban areas.
- Other Principal Arterials: All rural, non-Interstate principal arterials.
Rural Minor Arterial (Rural MnA):
Rural minor arterials supplement the rural principal arterial system and link cities, larger towns, resort areas, and other major traffic generators into a system providing interstate and inter-county service. They are spaced at intervals consistent with population density so that all developed areas of the state are within a reasonable distance of an arterial highway. These facilities should provide relatively high overall travel speeds with minimum interference to through movement.
Rural Collector Road (Rural MJ C, Rural Mn C):
Rural collector roads primarily serve travel of intra-county importance and constitute those routes on which predominant travel distances are shorter than on arterial routes. This system has two sub-classifications:
- Major Collector Roads: Provide service to county seats, larger towns, and other traffic generators of intra-county importance, which are not directly served by a higher system and link them to larger towns or routes with higher classifications. Examples of traffic generators for this classification include schools, shipping points, county parks, and important mining and agricultural areas.
- Minor Collector Roads: Provide service to remaining smaller communities, link locally important traffic generators to larger towns, and collect traffic from local roads. They should be spaced at intervals consistent with population density to bring all developed areas within a reasonable distance of a collector road.
Rural Local Road (Rural Loc):
Rural local roads primarily provide access to adjacent land and include trips over relatively short distances compared to the higher systems. This classification includes all rural facilities not included in one of the higher classifications.
Urban Principal Arterial (Urban Inst, Urban F&E, Urban PA):
Urban principal arterials should carry the major portion of traffic entering and leaving the urban area, as well as the majority of the through movements desiring to bypass the central city. Intra-city trips, including bus routes, such as between the central city and outlying areas, should also be served by this classification. In urban areas with a population under 50,000, routes within this system may be very limited in number and may be included only to provide continuity for rural arterials passing through the urban area. This system has three sub-classifications:
- Interstates: Interstate routes located within urban areas.
- Other Freeways and Expressways: All urban, non-interstate principal arterials with full control of access.
- Other Principal Arterials: All urban, non-interstate principal arterials with no control of access.
Urban Minor Arterial System (Urban Mn A):
Urban minor arterials interconnect with and enhance the urban principal arterial system and support trips of moderate length at a somewhat lower level of travel mobility. These facilities place more emphasis on land access than principal arterials, may carry local bus routes, and provide intra-community connections. Ideally, they should not penetrate identifiable neighborhoods.
Urban Collector Street (Urban C St):
Urban collector streets provide both land access and traffic circulation within residential, commercial, and industrial areas. These facilities collect traffic from local streets and channel it into the arterial system and also distribute trips by linking arterials with the ultimate destination. They may penetrate identifiable residential neighborhoods.
Urban Local Street (Urban Loc) :
Urban local streets primarily provide access to adjacent land and to the higher systems. These streets offer the lowest level of mobility and through traffic is usually deliberately discouraged. This classification includes all urban facilities not included in one of the higher classifications.