There are two major types of overhead signs:Ĭantilever: Cantilever signs are used to place a single sign or multiple smaller signs over one side of a highway.ĭifferent styles of cantilever signs include tapered steel tube, single steel tubular, and truss type construction. This reduces cost and improves safety by minimizing the number of separate structures needed. Whenever reasonably feasible, existing structures such as overpasses should be used for support of overhead signs. This allows the vehicle to safely pass under the sign after impact. When struck, the post slips off the foundation at the bottom, and rotates around the hinge plate below the sign panel (see diagram). The bottom plates are then bolted together at a specified torque. This is usually accomplished by adding a slotted plate to the top of the foundation post and another slotted plate to the bottom of the sign post, and by cutting the post just below the sign panel and adding a hinge system. The advantages of large steel I-beam posts are the ability to support very large sign panels, and the ability to quickly replace damaged posts by bolting a new post onto the existing breakaway foundation.ĭisadvantages include a difficulty in breaking away safely except in a single direction, unless special proprietary hardware is used.Īll large steel posts use a breakaway feature, unless protected by barrier or placed out of the clear zone. The upper portions of steel breakaway posts are often 'coped' or diagonally cut away to reduce the total weight of the post system. Sizes are defined by standard AISC beam designations. 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.īreakaway: This post type is characterized by an I-beam type shape. 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.ĭisadvantages 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. The sign panels are either bolted directly through the post or clamped to the outside of the post.

Sizes are defined by nominal steel tube diameters.

Tubular Steel: This post type is characterized by a round steel tube or pipe shape. Some sizes and combinations of square tube posts may require the use of slip bases or other breakaway features to meet crashworthiness criteria. 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.ĭisadvantages include a moderately higher cost per installation over U-channel. This is called creating a 'telescoping' post. Standard sizes range from 1 1/2 inches to 2 1/2 inches in 1/4 inchĪ square tube post can be made much stronger or spliced by inserting another smaller square tube post inside. Sizes are defined by outside square dimensions. Square Tube: This post type is characterized by a square shape, sometimes perforated by mounting holes at 1 inch spacings. No more than 3 U-channel posts should be used for a single sign without addition of a breakaway feature. '3 lb/ft post'.ĭisadvantages of U-channel include its lower loading capacity and the inability to mount signs at right angles on the same post. Sizes are defined by weight per foot i.e. 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. There are four primary types of steel shapes used for sign supports: Temporary sign posts can be made of non-treated wood. Permanent wood sign posts are made of redwood or pressure-treated softwoods. These posts usually come in sizes from 4x4 inches to 6x8 inches, with larger box beam sizes made of laminated plywood used for larger guide signs.Īll posts above 4圆 inch nominal size must be drilled perpendicular to traffic flow to allow the post to break away when struck by a motor vehicle, yet still maintain rigidity against wind forces and other non-impact loads. Wood posts are used in a number of states for permanaent or temporary signs.

Mash signpost specs