Chapter 3: Sign Materials and Supports
Section 1: Roadside Sign Supports
Introduction
Sign supports and their foundations are designed and constructed
to hold sign panels rigidly in the proper position. Supports should
resist swaying and failure due to wind or displacement by pedestrians
or vandals. When hit by a vehicle, a support should break away as
designed so that it does not pose a safety hazard to motorists.
The type of support depends primarily on the size of the sign.
A variety of shapes and sizes of support material are used.
Chapter 4 provides more information on maintenance of roadside
sign supports.
Foundations
Non-reinforced concrete drilled shafts are used as foundations
for small roadside supports that require foundations. Foundations
for large roadside sign supports greater than or equal to 24 inches in
diameter are reinforced concrete drilled shafts.
Design details for concrete foundations are shown on the
, “Sign Mounting Details” (SMD‑Series).
Types of Supports
Through the years, the Texas Department of Transportation (TxDOT) has used many types of roadside sign supports. Since the early 1960s, the emphasis has been on the yielding or breakaway sign supports. The TMUTCD requires sign supports to be crashworthy (breakaway, yielding or shielded) if the sign is within the clear zone. All TxDOT standard supports are crashworthy. TxDOT uses several kinds of breakaway supports. The
(SMD‑Series) detail all of the designs and the appropriate size sign to be mounted on each.
An approved list of crashworthy sign supports can be found on the
. These systems are to be installed as per manufacturer directions.
The following table lists the common types of roadside sign supports. Details and procedures for these supports may be found in the Traffic Engineering Standard Sheets (SMD‑Series).
Anchor System | Sign Post | Sign Area Range |
|---|---|---|
Wedge Anchor or Universal Anchor | Thin Wall Tube | ≤ 14 sq. ft |
Triangular Slip Base | 10BWG SCH80 | > 14 sq. ft., ≤ 24 sq. ft. > 24 sq. ft., ≤ 36 sq. ft. |
Slip Base with Fuse Plate | Steel I-Beams | Large Guide Signs |
Double post installations can hold up double the square feet. The area of the regulatory or warning sign supplementary plaques is included in determining the total sign area.
Signs mounted back-to-back on a single support need only use the square footage of one sign when determining the type of sign post as the wind load is the critical factor for the post capacity.