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FHWA Functional Classification Guidelines

Attachment 3 - Addendum

Note: This publication was updated in 2013. This version is for archival purposes. For the current version, see

Revised in 1989, this document was electronically scanned in April, 2000. The scanned image was processed through Optical Character Recognition software, the resulting text being formatted for the World Wide Web. Changes are restricted to:

Highway Functional Classification -
Concepts, Criteria and Procedures

This addendum supplements the manual, Highway Functional Classification - Concepts, Criteria and Procedures, March 1989, to provide more flexibility for classifying routes that cross urban boundaries and to provide specific criteria for including future or proposed routes.

Routes Crossing Urban/Rural Boundaries
The Manual provides for rural routes (other than principal arterials) to be upgraded to a higher classification level when they cross an urban boundary. Although the principle is sound, rigid application has presented difficulties for some states. Accordingly, this addendum to the guidelines is intended to provide greater flexibility for deciding on an appropriate place for changing the functional classification when rural routes cross an urban boundary, taking into account changes in traffic conditions, the degree of urban development and other factors. Instead of automatically upgrading the functional classification of a rural route that crosses an urban boundary, the rural classification may be continued inside the urban boundary until there is a more logical and acceptable place for a change.

Future Routes
The manual discusses procedures for conducting a functional classification based on projected facilities and usage for some "future year"; however, the manual does not provide criteria for including future or proposed routes into a functional classification of existing facilities. Because the functional classification will support the designation of the National Highway System which is expected to include some future routes, this addendum establishes criteria for determining which future routes should be included in the functional classification of existing routes. Future routes should be functionally classified with the existing system if they are included in an approved short range improvement program and there is a good probability that the route will be under construction in the reasonably near future (up to 6 years). Where applicable, the same classification should be given to the future route and to the existing route that it will replace until the future route is constructed.

Updated: 1/31/2017
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