Concept The concept of Functional Classification is not as mysterious or complex as it first appears. Most of us have an intuitive understanding that streets, roads, and highways serve different uses or "functions," and we act on this understanding when choosing a road or highway to meet our trip needs. We associate certain characteristics with certain types of facilities, and we classify or group them according to these characteristics. Even the names we give them often reveal a great deal about the general character of the facilities and the type of service we expect from them. They may suggest the locale of the facility, whether rural or urban; the volume, type, and speed of traffic typically using it; or even some of the physical features it is most likely to have such as multi-lanes or median divider. We may even associate a particular purpose of travel or type of trip with the name. We are more likely to take an Interstate rather than a “country road” when we need to drive a long distance in the shortest possible time. Directness of travel, high speeds, and minimal delay are some of the characteristics we associate with an Interstate highway. If we take the “country road” instead, we are choosing a very different trip and driving experience in terms of travel speeds, time, traffic volumes, and overall travel ease. For much the same reasons, we look for a “freeway” rather than a “local street” to take us across town or across county, hoping to avoid congestion and the stop and go traffic caused by signals and cross streets. But most of us prefer to live on “neighborhood streets” rather than “main highways” though we know that we must use the one to get to the other. “Boulevard,” “thoroughfare,” or “parkway” bring to mind other features and characteristics which we associate with these types of facilities. Sometimes our terminology is confusing if not contradictory. As someone pointed out, we still call some roads “freeways” even when there is a toll charge for using them. Many of our “expressways” resemble parking lots at rush hour. And we drive on “parkways” but park on “driveways.” Whatever we call them, our effort to classify streets and highways based on their general characteristics reveals an important point about the process. It is not an exact or precise science. It depends to a certain extent on experience and judgment, and no single measurement or criteria is sufficient to describe or define a class of roads. Nevertheless, the general concepts of each classification hold true no matter how much the details vary, and we have a relatively clear picture of what is meant when we talk about a “freeway,” an “Interstate,” or even a “main highway.” The Functional Classification system is similar in this respect. The criteria used to describe each class of highway must apply to a wide range of conditions in which the highway operates such as geography, population density, traffic volumes, highway spacing, and distance and speed of travel. While we may not be able to put exact figures to these measures and no one of them is sufficient to classify a highway, taken together they provide an effective set of guidelines for classifying and ranking different facilities. Definition Functional Classification is the grouping of roads, streets, and highways in a hierarchy based on the type of highway service they provide. Streets and highways do not operate independently. They are part of an interconnected network, and each one performs a service in moving traffic throughout the system. Generally, streets and highways perform two types of service. They provide either traffic mobility or land access and can be ranked in terms of the proportion of service they perform as shown in this diagram. At the top are Arterials. They include those classes of highways emphasizing a high level of mobility for the through movement of traffic. Land access is subordinate to this primary function. Generally, travel speeds and distances are greater on these facilities compared to the other classes. The highest classes of arterials, Interstates and freeways, are limited access to allow the free flow of traffic. Between these extremes are the Collectors whose name describes their function. They collect traffic from the lower facilities and distribute it to the higher. Collectors provide both mobility and land access. Generally, trip lengths, speeds, and volumes are moderate. At the bottom are Local streets and roads. Their primary function is to provide land access. Travel speeds, distances, and volumes are generally low, and through traffic is usually discouraged.   ODOT'S ROADWAY INVENTORY SYSTEM OF IDENTIFICATION OF THE FUNCTIONAL CLASSIFICATION OF A ROADWAY: 1 PRINCIPAL ARTERIAL - INTERSTATE (RURAL) 2 PRINCIPAL ARTERIAL - OTHER (RURAL) 6 MINOR ARTERIAL (RURAL) 7 MAJOR COLLECTOR (RURAL) 8 MINOR COLLECTOR (RURAL) 9 LOCAL (RURAL) 11 PRINCIPAL ARTERIAL - INTERSTATE (URBAN) 12 PRIN. ART.- OTHER FRWY/EXPRESSWY (URBAN) 14 PRINCIPAL ARTERIAL - OTHER (URBAN) 16 MINOR ARTERIAL (URBAN) 17 COLLECTOR (URBAN) 19 LOCAL (URBAN)     Functional Systems: Criteria and Characteristics In 1974, the Federal Highway Administration published the manual, Highway Functional Classification - Concepts, Criteria and Procedures. The manual was revised in 1989 and remains the definitive guide to the functional classification process. The manual defines the different functional systems, discusses the general concepts and characteristics used to identify each, and explains the procedures to follow in designating a system. The following discussion is based on this manual. Functional Classification is divided into rural and urban systems. The urban functional classification system covers all streets, roads, and highways located within urban boundaries designated by the U.S. Census Bureau. The Bureau defines two types of urban areas based on population. Small urban areas are urban places with a population or 5,000 or more and not located within any urbanized area. An urbanized area is an area with a population of 50,000 or more. As might be expected, the rural functional classification system covers all other streets, roads, and highways that are not located within the boundaries of small urban and urbanized areas. While urban and rural areas differ, for example, in terms of the density of land use and intensity of traffic and travel, the same general functional concepts apply to both systems. Streets and roads are ranked according to their purpose or function in meeting the demands for mobility and land access. The principal difference between the two systems is the length of trips both in time and distance. Rural Functional Classification System The rural functional classification system consists of all highways located outside urban and urbanized area boundaries. There are four classes of highways in the rural system: principal arterials, minor arterials, major and minor collectors, and locals. The characteristics of each class are as follows: Class Characteristics 1. Rural Principal Arterial a. Serve corridor movements having trip length and travel density characteristics indicative of substantial statewide or interstate travel; b. Connect all or nearly all urban areas with 50,000 and over population and the majority of urban areas with 25,000 and over population; c. Provide an integrated network of continuous routes. * The Rural Interstate highway system constitutes a subsystem of Rural Principal Arterials and is composed of those routes specifically designated as Interstate highways. All other non-Interstate principal arterials are included in the subsystem Rural Other Principal Arterials. 2. Rural Minor Arterial a. Connect cities and larger towns (and other major destinations such as resorts capable of attracting travel over long distances) and form an integrated network providing interstate and intercounty service; b. Spaced at intervals so that all developed areas are within a reasonable distance of an arterial; c. Provide service to corridors with trip lengths and travel density greater than those served by rural collectors and local roads and with relatively high travel speeds and minimum interference to through movement. 3. Rural Collectors a. Serve primarily intracounty rather than statewide travel; b. Serve more moderate travel speeds and distances than those on arterial routes. There are two subclasses of Rural Collectors. (1). Rural Major Collectors (a) Provide service to any county seat, larger towns, and other county destinations such as consolidated schools, parks, or important mining and agricultural area not served by an arterial; (b) Connect these places with nearby larger towns and cities or with arterial routes; (c) Serve the most important intracounty travel corridors. (2). Rural Minor Collectors (a) Are spaced at intervals to collect traffic from local roads and bring all developed areas within reasonable distance of a collector; (b) Provide service to smaller communities not served by a higher class facility; (c) Connect locally important traffic generators with rural hinterlands.

4. Rural Locals	a. Provide access to adjacent land;
	b. Serve travel over relatively short distances.

Urban Functional Classification System The urban functional classification system consists of all roads, streets, and highways located inside the urban/urbanized area boundary. There are four classes of highway in the urban system: urban principal arterials, urban minor arterials, collector streets, and local streets. Because of the greater concentration of population, more intense land use, and higher traffic volumes in the urban area compared to rural, some characteristics of urban classes differ slightly from their rural counterparts, for example in the density and spacing of the urban network and in the volume and length of trips.