New Wind Design Criteria for Traffic Signal Support Structures

The American Association of State Highway and Transportation Officials (AASHTO) Standard Specifications for Structural Supports for Highway Signs, Luminaries and Traffic Signals has been revised in its entirety through a major research project conducted under the auspices of the National Cooperative Highway Research Program (NCHRP Project 17-10). The new document was approved in 1999 by all state departments of transportation for adoption by AASHTO and was published in 2001. The revisions include updated provisions and criteria for extreme wind loads and new provisions and criteria on fatigue design. These provisions differ considerably from those in previous editions of the specifications. The impact of the new wind load and fatigue provisions on the design of traffic signal supports from the standpoint of safety and economy had not been studied and was the main goal of this project. Wind load calculations and design of a span wire traffic signal structure in Alabama were performed using the design criteria in both the 2001 AASHTO specifications and the 1994 edition of the specifications. The results were compared and the impact of the 2001 specifications on design of span wire traffic signal structures in Alabama was illustrated.