Division 600 — Section 657
600-236 Section 657 — Overhead Sign Structures
657.1 Description
1 Furnish, fabricate, and install new overhead sign structures . Refurbish, modify, or remove exiting overhead sign structures. Furnish, fabricate, and install sign lighting systems.
657.1.1 Types of Overhead Sign Structures
1 This Section contains characteristics for the following types of overhead sign structures: • Cantilever Structure – One vertical support with an arm extending over the roadway. The cantilever arm is limited to 45 ft in length. • Sign Bridge – Spans the entire roadway or a roadway in a single direction and has supports at either end. The vertical supports on either end may have an integral foundation built in to a bridge parapet, median barrier, or retaining wall. • Butterfly – Single vertical support, usually installed on integral footings in median barriers along urban freeways or highways having six or more traffic lanes. Signs can be mounted on both sides (back to back) of the structure. • Bridge Mounted – Structure attached to a bridge overpass over the highway. Structures are normally erected perpendicular to the traffic lanes if the roadway bridge is skewed but may be slightly skewed to the traffic lanes where the bridge skew is great. A single sign assembly can be made up of two or more individual structures mounted together where there is an extreme skew or length. • Span -wire Structure – Two concrete or steel stain poles with a cable across the roadway. Signs are mounted on the cable using clamps, and tether cables are included to keep the signs stable in high winds. 2 The structure type, illustration of sign panel dimensions, span lengths, vertical and horizontal clearances, subsurface data when possible, and design wind loads are shown on the Plans. Unless otherwise noted, mount all signs with their horizontal centerl ines on the same level with the horizontal centerline of the structure.
657.1.2 Structural Designs
1 Design the overhead sign structure and provide Shop/Working Drawings that conform to these specifications, the Special Provisions, latest AASHTO
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