Structural and Safety Investigation of Statewide Performance of Weathered Steel Beam Guardrail in North Carolina

Abstract

This paper evaluates the structural integrity and safety performance of weathered steel beam guardrail (WSBG) in North Carolina. WSBG is a popular alternative to galvanized steel guardrail (GSG) in that it is an aesthetic solution that blends in with the surrounding natural environment. A New Hampshire study, however, found that WSBG deteriorates more quickly. That study prompted an FHWA recommendation discouraging the use of WSBG across the country. This paper describes a comprehensive study of all WSBG installations in North Carolina, where weather conditions and deicing practices are generally much less severe than in New Hampshire. The research results did not show any trends of deteriorating thickness as a function of guardrail age (the oldest installation was almost 30 years old), elevation (the tallest installation was 4,200 ft), and annual average daily traffic (the highest traffic volume was 27,000 vehicles per day). The WSBG at all 25 test sites was shown to be above AASHTO minimum thickness specifications of 0.096 in. at a 95% confidence level. From a safety perspective, the research results suggested a lower percentage of injury collisions at WSBG installations relative to GSG installations at comparison sites, although low crash sample sizes made a more robust comparison difficult. Overall, this research suggests there are no structural concerns about using WSBG in North Carolina. The findings of this study may have broader policy implications for other states.

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