Thesis (M.S., Civil Engineering)--University of Idaho, June 2014 | This study evaluates the safety performance of the IdaShield experimental warning sign via crash data analysis, user assessment surveys, and driving simulation. Highway-rail crossing inventory and crash data from the Idaho Transportation Department and Federal Railroad Administration were used to develop a Safety Performance Function (SPF) for passive highway-rail crossings. A Highway Safety Manual Before/After Empirical Bayes analysis was performed using the SPF and revealed a significant decrease in crash frequency after the 1997 - 1998 IdaShield installations. This is the first study to develop a highway-rail crossing SPF and also use the SPF in the HSM Empirical Bayes method to evaluate the effectiveness of a sign treatment. A statistical comparison between nighttime and daytime crash frequency reduction due to IdaShield installations showed that the IdaShield performs notably better at nighttime relative to daytime. User assessment surveys and driving simulation revealed that drivers assign a "yield" meaning to the IdaShield.