Highway and traffic signs use a number of different types of supports.

Wood and steel are the two primary materials used for small sign supports. Larger sign supports, such as cantilever structures or sign bridges, are usually made of steel. Other metals such as aluminum may be used.

Steel Posts

 

There are four primary types of steel shapes used for sign supports:

U-Channel: This post type is often preferred for maintenance and light construction applications, since it is easy to directly drive into the ground and assemble, and has low cost. Sizes are defined by weight per foot; i.e. "3 lb/ft post".

Disadvantages of U-channel include its lower loading capacity and the inability to mount signs at right angles on the same post.

 

No more than 3 U-channel posts should be used for a single sign without addition of a breakaway feature.

 

Square Sign Post

This post type is characterized by a square shape, sometimes perforated by mounting holes at 1 inch spacings. Sizes are defined by outside square dimensions. Standard sizes range from 1 1/2 inches to 2 1/2 inches in 1/4 inch increments.

A square tube post can be made much stronger or spliced by inserting another smaller square tube post inside.

The advantages of square tube posts are excellent flexibility in mounting options, greater loading capacity over U-channel, the ability to mount signs on 4 sides of the post, and the ability to quickly replace damaged posts by pulling the old post out of the foundation and inserting a new post.

Disadvantages include a moderately higher cost per installation over U-channel.

 

Some sizes and combinations of square tube posts may require the use of slip bases or other breakaway features to meet crash worthiness criteria.

 

Tubular Steel

This post type is characterized by a round steel tube or pipe shape. Sizes are defined by nominal steel tube diameters. The sign panels are either bolted directly through the post or clamped to the outside of the post.

The advantages of tubular steel posts are low cost, the ability to use commonly available steel pipe, and the ability to mount signs at any desired angle.

Disadvantages include the need to field-drill the post or use special clamps to attach signs, and the requirement to use special proprietary breakaway hardware for larger post sizes if installed in the clear zone.

 

There are variants on tubular posts offered by vendors that use a different shape and cross-section for the post, but share many of the same characteristics as standard tubular posts.