Traffic signs are a primary source of information to motorists. The majority of traffic signs consist of sign panels held in place by a single support. Single supports can usually be used for signs as large as 18 ft2 (1.7 m2) in area. The only purpose of the sign support is to hold the sign at the proper position for driver visibility. This requires that this support be strong enough to maintain the sign panel in its intended position while subjected to wind, ice, and snow loads. The magnitude of these forces increases as the sign panel becomes larger in size, until the panel is so large that multiple supports are required. Single sign supports are made of different materials, of various sizes and configurations, each capable of withstanding different environmental loads. Considering only the environmental loads and selecting a support system to hold the sign panel at the proper position can result in severe vehicular damage and occupant injury upon impact. Proper sign installation requires that the sign assembly be able to hold its proper position and give way under impact to minimize severity to an errant vehicle and its occupants. This requires the proper design in sign system selection and placement.
Sign supports are classified as single-support and multiple-support systems. Single sign support refers to a support that has no other support, or fixed object, within a 7-ft (2100-mm) radius [18]. Multiple supports refer to installations that are spaced less than 7 ft (2100 mm) from each other, or from other fixed objects. With the closer spacing, it is possible for a vehicle, leaving the roadway at an angle, to impact more than one fixed object or support at a time. Support systems that provide acceptable performance when struck alone can result in severe occupant injury when struck simultaneously with another support. The discussion of this article pertains to single sign supports (i. e., supports installed no closer than a 7-ft (2100-mm) radius to other sign supports or fixed objects). The single mount support types that are used by most agencies include U-channel, wood, square steel tube, and steel pipe. Descriptions of other single mount post types, such as aluminum and fiberglass, are provided at the following FHWA sign support website: http://safety. fhwa. dot. gov/roadway_dept/ road_hardware/signsupports. htm
