United States Department of Transportation
i
Updating and Implementing the Grade Severity Rating System for Wyoming Mountain Passes: Evaluating the Safety Effectiveness of Downgrade Warning Signs [Volume 2]
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2018-12-01
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[PDF-7.74 MB]
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Edition:Final Report
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Abstract:Truck safety on mountain passes presents a major challenge to most highway agencies in western United States. Large trucks are known to be disproportionately affected on severe downgrades which characterize mountain passes in comparison to other vehicle classes due to large sizes and heavy loads. The Wyoming Department of Transportation in an effort to reduce crash risks on Wyoming mountain passes has among other measures installed warning signs on steep grades in the state. The main purpose of this study is to develop recommendations of the best warning system on Wyoming mountain passes based on an evaluation of the impact of warning signs on truck crashes. Hazardous downgrades in the state were identified and data was collected to build a crash database. Several analyses were then conducted to evaluate the impact of advance downgrade warning signs on truck crashes. The analyses included propensity score matching, negative binomial modeling, and ranking of sites and a hotspot analysis of warning sign placement. The potential use of intelligent transportation systems in reducing downgrade truck crashes was assessed as well. The results of the analyses indicate that the various downgrade warning signs are effective in preventing downgrade crashes on mountain passes.
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