Manual of Traffic Signs

From the American Association of State Highway and Transportation Officials (AASHTO)


(Revised September 15, 1970)

The purpose of the U.S. road numbering and marking system is to facilitate travel on the main interstate lines, over the shortest routes and the best roads. To serve that purpose a system of main interstate routes was designated, and a uniform system of guide and warning signs was adopted for use in all the States, on such designated routes. This system was established in 1926. It has passed the preliminary development state. It has reached the period of review, revision, and consolidation. The U.S. road system now needs perfecting rather than expansion.

New construction has opened up newer, better and shorter routes. Demands of interstate traffic have increased and are more exacting. Public acceptance of the U.S. numbered system has made possible the rectification of early concessions made for the purpose of getting the system established and marked.

In harmony with the improved condition of State roads, the State route markers of the several States have more and more become a dependable trade mark of quality in those routes.

The establishment of a U.S. number as a guide for interstate travel over certain roads has no connection with federal control or the designation of Federal funds for road construction. These numbers may recognize a State road which has been constructed entirely by the use of State funds.

Often the U.S. marker is interpreted by the public as identifying a "federal highway" whereas the routes making up the U.S. numbered system are under State jurisdiction and not under Federal jurisdiction.

It was never intended that the U.S. numbered system should absorb or supplant the State numbered routes. It is intended by uniform marking of a U.S. route in two or more States, to facilitate the movement of Interstate traffic. Thus, with a relatively limited mileage, the U.S. numbered road system must meet the changing conditions if it is to endure and serve the purpose for which it was intended.

The routes comprising the National System of Interstate and Defense Highways will be marked with its own distinctive route marker shield and will have a numbering system that is separate and apart from the U.S. numbered system. The Interstate system marking and numbering is not to replace that of the U.S. system, but is, in reality, a separate system of a limited mileage of modern expressways to accommodate major streams of traffic between the Nation's major traffic generating areas and the two numbered systems will complement each other. A large extent of the Interstate system is developed on new location. Those sections where the Interstate system is developed over an existing U.S. numbered route, both the U.S. and the Interstate system shields and route numbers shall be used to mark those sections which are coincident. Otherwise, it is assumed that in the majority of instances the U.S. markers and numbers will remain on the routes as now established or as determined by subsequent Executive Committee action, as new construction makes available new and better routes.

Established Policies

  1. The Executive Committee of the American Association of State Highway and Transportation Officials shall have full authority to review the U.S. numbered road system and the numbering and marking thereof, to make additions, changes, extensions, revisions or reductions in said road system and to revise the numbering or marking thereof.

  2. Before approving any addition, change, extension, revision or reduction in the U.S. numbered road system or the numbering or marking of any U.S. numbered road, the Executive Committee shall consult the State Highway Department of the State or States through or within which such addition, change, extension, revision or reduction is located.

  3. The State Highway Department, by a favorable vote on the adoption of this program and policy, agrees and pledges its good faith that it will not erect U.S. markers on any road or take down or change the U.S. markers on any road without the authorization, consent or approval of the Executive Committee of the American Association of State Highway and Transportation Officials, notwithstanding the fact that the changes proposed are entirely within that State.

  4. No additional road shall be added to the U.S. numbered road system, and no existing U.S. road shall be extended except where there is a definite showing of an adequately improved highway carrying an established and necessary line of interstate traffic not otherwise provided for by existing U.S. routes and for which traffic adequate service cannot be provided by State route numbers.

    Extension of present U.S. numbered routes may be made only when the proposed extension is in the general direction of the present route.

    Proposed extensions shall not be made when, to do so, it is necessary to duplicate U.S. routes already established, unless the duplication is for a short distance and the routes then diverge, ending in different terminal points.

  5. No new U.S. route located wholly in one State shall be established. U.S, routes, less than three hundred miles in length, heretofore established and located wholly in one State, shall be eliminated either by consolidation with other U.S. routes or by reverting to State routes, as rapidly as the State Highway Department and the Executive Committee of the American Association of State Highway and Transportation Officials can reach agreement with reference thereto.

  6. The Executive Committee shall encourage the State Highway Departments in the development of continuous State route numbers extending into two or more States rather than the establishment of additional U.S. numbered routes, and shall encourage the substitution of continuously numbered State routes for relatively short U.S. routes now located in two or more States.

  7. No new divided numbers (such as U.S. 96-W and U.S. 96-E, etc.) shall be adopted. Existing divided U.S. numbers shall be eliminated as rapidly as the State Highway Department and the Executive Committee can reach agreement with reference thereto.

  8. Existing U.S. routes shall be consolidated, improved and shortened

    1. By connecting two or more relatively short routes into one longer route.

    2. By relocating portions of existing routes so as to follow newer, better or shorter roads.

    3. By establishment of new numbers, following in general existing U.S. numbered routes but taking advantage of new roads or short cuts where the changing of present numbers is not practical.

  9. A suitable highway legend, which may be copyrighted, shall be adopted by the Executive Committee. Such legend will be recommended for use to all travel map makers, also for use by the State Highway Departments. This legend is to show, In a uniform manner, the suitability for travel not only of the U.S. numbered routes but also of State routes.

  10. Any proposal that would exploit the prestige of the U.S. numbered highway system to direct traffic over routes that are not the shortest and best available between major control points on the system, especially when it appears to be for the purpose of benefiting businesses located along such a proposed route, shall constitute reason for denying any application to make such an addition to the system.

  11. Since the U.S. numbered system was established by joint action of the State Highway Departments, only those applications for changes in or additions to the U.S. numbered system from the member State Highway Department involved shall be considered by the Executive Committee. Those local officials, organizations, groups, or Individuals interested in a change or in an addition to the system should contact their State Highway Department and not the Executive Committee. The Executive Committee shall consider only those applications from State Highway Departments that are filed on the official form and are complete in all detail to the degree that the Executive Committee can evaluate the need for and adequacy of the proposed route from the application form submitted and without a representative of the State Highway Department appearing before Committee to supply additional information.

  12. No person or group of persons shall be allowed to appear either before the Executive Committee or its Special Committee on U.S. Route Numbering except in the case of a State Highway Department requesting reconsideration of an action by,the Executive Committee in regard to an application filed by that Department.

  13. In case a proposed change in or addition to the U.S. numbered system involves two or more States, the proposal shall be given official consideration only when all affected State Highway Departments have filed applications to cover the complete proposal.

  14. No route should be considered for inclusion in the U.S. numbered system that does not substantially meet the current AASHTO design standards.

  15. Any toll highway facility may be included in the U.S. Numbered System when it meets all the criteria for inclusion, and when the request for the marking originates with the official authority having jurisdiction over the toll facility and the request is directed to AASHTO and supported by the appropriate Member Department. The word "Toll" shall appear over the official U.S. Route Marker and a toll free routing between the same termini shall continue to be retained and marked as a part of the U.S. Numbered System.

These purposes and policies, having been amended and approved by the State Highways Departments after individual State consideration, the Executive Committee of the American Association of State Highway and Transportation Officials hereby promulgates and makes effective these policies upon the authority of the State Highway Departments, beginning September 15, 1970.

It is realized that this work is a continuing obligation and that even reforms made evident from past experiences cannot be accomplished at once. It is the judgment of those to whom this obligation has been delegated, that all far-seeing citizens will aid the State Highway Departments in their efforts to make this numbering system of the greatest use to the traveling public.

In this connection it should be noted that while additional routes for U.S. numbering will be greatly limited, that stress will be laid upon the availability of many State numbered routes for interstate travel. Map makers will be urged to recognize U.S. numbered roads and well established State numbered roads as of equal importance - both to be printed in the same color.

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Updated 15 September 2010 (coding)

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