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System Classifications

Federal laws and regulations assign states the primary responsibility for developing, updating and adopting a Statewide Functional Classification and Urban Boundary Map.

Functional classification is the process by which streets and highways are grouped into classes, or systems, according to the character of service they are intended to provide. Basic to this process is the recognition that individual roads and streets do not serve travel independently in any major way. Rather, most travel involves movement through a network of roads. It becomes necessary then to determine how this travel can be channelized within the network in a logical and efficient manner. Functional classification defines the nature of this channelization process by defining the part that any particular road or street should play in serving the flow of trips through a highway network.

The Federal Highways Administration made revisions to the Highway Functional Classification: Concepts, Criteria and Procedures 2013 Edition guidebook (located in the documents section). The most significant change is the reduction of the number of functional classification codes due to the consolidation of rural and urban designations. The revised functional classification codes now are:

  • 1 = Interstate
  • 2 = Other Freeways and Expressways
  • 3 = Other Principal Arterial
  • 4 = Minor Arterial
  • 5 = Major Collector
  • 6 = Minor Collector
  • 7 = Loacl Roads

Moving Ahead for Progress in the 21st Century (MAP-21) is the latest Transportation Bill and was signed into law by President Obama on July 6, 2012. Among the many changes in MAP-21 is a new definition of the National Highway System (NHS). As of October 1, 2012, the NHS will automatically be expanded to include all roads that have a federal functional classification of principal arterial or higher.

Idaho's impact: About 470 miles of principal arterials - including many local roads - will be added to the NHS. These routes will be subject to federal design standards as the result of this designation and a number of new federal performance measures are required on all NHS. Local governments may want to consider reviewing their functional classification designations of some marginal principal arterials. FHWA guidance is anticipated by 12/31/12.

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Another important systems adjustment consideration is urban boundary and how changes to a urban boundary can affect the overall transportation system. Every 10 years, the US Bureau of the Census reviews urban growth. Approximately, 2-years after the decennial census is conducted, the Census Bureau distributes Urban Area Boundary maps or data in which maps can be created. All cities over cities over 5,000 population and metropolitan transportation orgianization must review the potential census boundary changes and either accept them as is or adjust them for transportation planning purposes. While the urban/rural designation is independent of the functional classification, it is important to recognize that the adjusted urban area boundary is a significant factor in developing the functional classification of a road in an urban/rural context.

If ITD or local planning agencies choose not to adjust the urban growth boundaries (or otherwise unable to do so within two years of the release of the Census Bureau boundaries), the most recent unadjusted census boundaries will take effect, and the appropriate modifications to the HPMS roadway databse will need to be made to reflect the new urban/rural boundaries. This could cause a roadway privisously considered ot be urban to now be considered rural, which may affect the Federal-aid funding eligibility.

Functional Classification and Urban Boundary Update Procedures

FHWA Directive 23 CFR 470 states that the State transportation agency has the primary responsibility for developing and updating a statewide highway functional classification to determine functional usage of the existing roads and streets. The State transportation agency is to cooperate with responsible local officials, or appropriate Federal agency in the case of areas under Federal jurisdiction, in developing and updating the functional classification. The results of the functional classification is to be mapped and submitted to FHWA for approval and when approved serve as the official record for Federal-aid highways and the basis for designation of the National Highway System.

The functional classification map access through the following link reflects the Federal Functional Classification for Idaho as defined and approved by the Federal Highway Administration (FHWA). The map is updated after each census and periodically between decennial censuses.

The functional classifcation and urban boundary system is revised periodically to reflect the changing conditions brought on by regional development. There are two specific circumstances in which adjustments are generally considered:

1. Statewide Updates. Upon the release of the US Census, data becomes available for review; thus, truggering the review and possible updates to adopted systems and boundaries to reflect the anticipated functional usage witha 10-year target date. Approximately, two to three years after the Decennial Census modifications are made, itis recommended to anticipate the next round of proposed changes.

2. State Highway System Updates and Special Cases. As outlines in Board Policy B-09006, if a request is made to revise the current approved system, revisions will be made on case-by-case bases. Such revisions may be initiated by the Local Highway Technical Assistance Council (LHTAC), a local highway jurisdiction or at the request of said jurisdiction by the District Engineer, District Senior Transportation Planner, the Planning/Program Management (2PM) Section or designee.

If updates are requested for project funding reasons, the local jurisdiction should initiate requests prior to the beginning of the Federal program year (October 1st) corresponding to the project authorization to ensure timely approval by LHTAC; however, updates may be requested at any time.

All requests (whether it is a system-wide update or a special case) will follow the five step process shown on the following page. Each request is required to be submitted using the ITD Functional Classification/Urban Boundary Change Request Form. The form outlines all required information and submittal requirements.

System Adjustments Update Procedures

All requests for adjustment (addition, removal and/or other system action) to the SHS shall be referred to the Board Subcommittee on State Highway System Adjustments for consideration before department staff undertakes any actions or studies. Upon review of the request for a State highway System Adjustment, the Board Subcommittee shall direct the Chief Engineer to conduct an analysis to determine the highway’s operating and network characteristics using a rating criterion that has been reviewed and approved by the Idaho Transportation Board. When a SHS action is warranted, the Board Subcommittee, with assistance from the appropriate District Engineer or a delegate shall negotiate with the local highway jurisdiction on the proposed adjustment.

In the event that the department establishes a new state highway such as, but not limited to, an alternate route, bypass, and .or interchange, the Board Subcommittee and the District Engineer shall work closely to negotiate state highway adjustments with the local highway jurisdiction prior to the project moving from the Early Development Program into the Statewide Transportation Improvement Program (STIP). The Board Subcommittee and the District Engineer are to be creative and consider all feasible options in the negotiations, including financial assistance or maintenance assistance such as snowplowing or striping. The full Idaho Transportation Board shall have final approval of all transactions on the State Highway System. Adjustments shall be accomplished by an “Official Minute” of the Idaho Transportation Board. The department and the local highway jurisdiction shall sign a cooperative agreement whenever needed to clarify responsibilities and other specifications.

For further information please call or email Maranda OBray, Transportation Planner: (208) 334-8483

Page Last Modified: 9/30/2013 3:46:00 PM

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Idaho Transportation Department
3311 W. State Street · P.O. Box 7129
Boise, ID 83707-1129