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(1) No mailbox or newspaper delivery box (hereafter referred to as "mailbox") will be allowed to exist on any highway under the jurisdiction of the highway commission if it interferes with the safety of the traveling public or the function, maintenance, or operation of the highway system. A mailbox installation that does not conform to the provisions of this regulation is an unauthorized encroachment under Title 60, chapter 6, part 1, MCA. The location and construction of mailboxes shall conform to the rules and regulations of the U.S. postal service as well as the standards established by the department. The standards of the department for the location and construction of mailboxes are available from:


     Montana Department of Transportation

     2701 Prospect Avenue

     Helena, MT 59620

(2) A mailbox installation that conforms to the following criteria will be considered acceptable unless in the judgment of the department the installation interferes with the safety of the traveling public or the function, maintenance, or operation of the highway system.

(a) No mailbox will be permitted where access is from the lanes or shoulders of limited access or controlled access facilities or where access is otherwise prohibited by law or regulation.

(b) Mailboxes shall be located on the right-hand side of the roadway in the direction of the delivery route except on one-way streets where they may be placed on the left-hand side. The bottom of the box shall be set at an elevation established by the U.S. postal service, usually between 3'6" and 4'0" above the roadway surface. The roadside face of the box shall be offset from the edge of the traveled way a minimum distance of the greater of the following: 8 feet (where no paved shoulder exists) , the width of the all-weather shoulder present plus 8 to 12 inches, or the width of an all-weather turnout specified by the department plus 8 to 12 inches.

(c) Exceptions to the lateral placement criteria above will exist on residential streets and certain designated rural roads where the department deems it in the public interest to permit lesser clearances or to require greater clearances. On curbed streets, the roadside face of the mailbox shall be set back from the face of curb a distance between 6 and 12 inches. On residential streets without curbs or all-weather shoulders that carry low-traffic volumes operating at low speeds, the roadside face of a mailbox shall be offset between 8 and 12 inches behind the edge of pavement. On very low-volume rural roads with low-operating speeds, the department may find it acceptable to offset mailboxes a minimum of 6'8" from the traveled ways and under some low-volume, low-speed conditions may find clearances as low as 2'8" acceptable.

(d) Where a mailbox is located at a driveway entrance, it shall be placed on the far side of the driveway in the direction of the delivery route.

(e) Where a mailbox is located at an intersecting road, it shall be located a minimum of 100 feet beyond the center of the intersecting road in the direction of the delivery route. This distance shall be increased to 200 feet when the average daily traffic on the intersecting road exceeds 400 vehicles per day.

(3) (a) Mailboxes shall be of light sheet metal or plastic construction conforming to the requirements of the U.S. postal service. Newspaper delivery boxes shall be of light sheet metal or plastic construction of minimum dimensions suitable for holding a newspaper.

(b) No more than two mailboxes may be mounted on a support structure unless the support structure and mailbox arrangement have been shown to be safe by crash testing. However, light- weight newspaper boxes may be mounted below the mailbox on the side of the mailbox support.

(c) Mailbox supports shall not be set in concrete unless the support design has been shown to be safe by crash tests when so installed.

(d) A single 4-inch x 4-inch or 4 1/2-inch diameter wooden post or a metal post with a strength no greater than a 2-inch diameter standard strength steel pipe and embedded no more than 24 inches into the ground will be acceptable as a mailbox support. A metal post shall not be fitted with an anchor plate, but it may have an anti-twist device that extends no more than 10 inches below the ground surface.

(e) The post-to-box attachment details should be of sufficient strength to prevent the box from separating from the post top if the installation is struck by a vehicle. The May 24, 1984 edition of the AASHTO (American Association of State Highway and Transportation officials) publication "A Guide for Erecting Mailboxes on Highways" has been used as a guide for this rule and is incorporated by reference. Please refer to Figures I, III, and V of said document for acceptable attachment details, and Figures II, IV, and V, which show acceptable mailbox support assemblies. (Copies of all AASHTO publications referenced in these rules are available for inspection and copying at the department's offices in Helena. Copies of current AASHTO publications are available for purchase from the American Association of State Highway and Transportation Officials, Suite 225, 444 North Capital Street, NW, Washington, DC 20001.)

(f) The minimum spacing between the centers of support posts shall be three-fourths the height of the posts above the groundline.

(g) Mailbox support designs not described in this regulation may be acceptable if specifically approved by the department.

(4) It will be the responsibility of the postal patron to inform the department of any new or existing mailbox installation where shoulder construction is inadequate to permit allweather vehicular access to the mailbox.

(5) Any mailbox that is found to violate the intent of this regulation shall be subject to the notification and removal provisions found in sections 60-6-101 through 60-6-105, MCA.

History: Sec. 60-6-101 MCA; IMP, Sec. 60-6-101 MCA; NEW, 1992 MAR p. 1868, Eff. 8/28/92.

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