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Mailbox Support Installation

Where to install a mailbox along a public road

Mailboxes shall be placed for maximum convenience to the patron, but shall be consistent with safety considerations for highway traffic, the carrier, and the patron. Mailbox locations shall minimize the walking distance within the roadway for the patron, maximize the stopping sight distance in advance of the mailbox, and shall not restrict the sight distance exiting the driveway. The placing of mailboxes along high-speed highways should be avoided if other practical locations are available.

Mailboxes shall be located on the far right side of the highway in the direction of travel. The bottom of the box shall be set at an elevation of 42 to 48 inches above the roadway surface as established by the U.S. Postal Service. The roadside face of the mailbox shall be located so that it is:

    • 8 -12 inches outside of the paved or aggregate shoulder, or
    • 6 -12 inches back from the face of the curb

Where a mailbox is located near an intersection or driveway, it shall be in accordance with local ordinances and/or policies. If a mailbox is installed near an existing guardrail, it shall be located behind the guardrail, where practical.

Exceptions to these mailbox locations requirements must be approved by the St. Louis County Public Works Department and the local Postmaster.

Mailboxes shall conform to the requirements of the U.S. Postal Service, Minnesota Rules Chapter 8818 and shall be acceptable to the St. Louis County Public Works Department. No more than two mailboxes shall be mounted on a support structure.

All new and replacement mailbox supports shall meet the St. Louis County Public Works Department standard specifications for swing-away mailbox support design. The attached drawing and specifications are from MnDOT Standard Plate 9350A.

The metal support shall weigh three pounds per linear foot or less and shall not be fitted with an anchor plate. The post must be embedded a minimum of four feet below ground and project at least two feet or more above ground as needed depending on roadway in-slope. The minimum spacing between the centers of support posts shall be thirty inches.

The post-to-box attachments 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 exact support hardware dimensions and design may vary. The product must result in a satisfactory attachment of the mailbox to the post, and all components must fit together properly.

There are several swing-away mailbox supports manufactured for sale to the public. It is acceptable for residents to purchase and install these products if the product has passed NCHRP 350 crash requirements and meets Minnesota Rules Chapter 8818.

Exceptions to these mailbox structure designs must be approved by the St. Louis County Public Works Department and the local Postmaster.

Spacing of Mailbox Supports
In accordance with Minnesota Rules Chapter 8818, mailbox supports shall be spaced no closer than thirty inches.

Miscellaneous Attachments to Mailbox Supports
Newspaper delivery boxes, advertisement delivery boxes, nameplates, address plates, etc., shall not be installed underneath the mailbox, whether attached to the mailbox support or on a separate post. The area underneath the mailbox shall remain free of obstructions in order to allow the unhindered passage of the snowplow wing blade. Obstacles interfering with the wing blade force the plow to swerve, often into the oncoming lane, creating an unsafe situation for motorists and plow operators.


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Related Topics

 Mailbox Support Diagram 


 NCHRP Report 350 
 MN Admin. Rule 8818