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Structural Supports For Highway Signs, Luminaires And Traffic Signals
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STEEL MAST ARM ASSEMBLIES

The use of steel mast arm assemblies for traffic signal installations is normally detailed in the plans by the Office of Traffic Safety and Design and the work is controlled under the following sections of the Georgia Standard Specifications:

  1. SECTION 639 - Strain Poles for Overhead Sign and Signal Applications

  2. SECTION 915 – Mast Arm Assemblies

To limit serviceability concerns due to high amplitude wind vibrations as well as structural concerns due to fatigue loading, steel mast arm assemblies shall be limited by this policy to lengths not to exceed 65 feet.

Exceptions to this policy may be granted for the following reasons:

  1. Safety - Longer mast arm assemblies may be used if it is determined that the proposed mast arm installation location has a high accident history and the use of the longer mast arm assembly provides a safer condition than a span wire or sign bridge assembly or if greater clear zone areas can be obtained with the use of longer mast arms as opposed to span wire or span bridge arrangements.

  2. Right of Way - Longer mast arm assemblies may be used if it can be demonstrated that the proposed installation location has Right of Way concerns that make a span wire or sign bridge assembly impracticable or prohibitively expensive.

  3. Local Governments – If the proposed installation is on a local road and the installation is to be maintained by the local government longer mast arm assemblies may be approved provided;

    1. The local government agrees to hold harmless the Department from any future failure of the assembly,
    2. The assembly meets appropriate design criteria as determined by the Department and,
    3. The local government agrees to fund any additional cost as a result of the use of the longer mast arm assembly.

Exceptions to the 65 foot limit for mast arm assemblies shall be approved by the Chief Engineer on a case by case basis. Exceptions shall be granted only after submittal of documentation indicating the appropriate safety or right of way concerns and/or appropriate agreements from local governments and providing sufficient information to justify the need for the exception.

In all cases requesting an exception, every effort should be made to keep the mast arm assembly length as close to the 65 foot limit as possible.

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