Fully Bayesian Approach to Investigate and Evaluate Ranking Criteria for Black Spot Identification

Abstract

The fully Bayesian (FB) approach for identification of collision black spots has been available for some time. However, little research has been conducted on the performance of the FB method, especially on criteria for ranking sites. A study was done to fill this void by a thorough evaluation of the FB method for black spot identification. First, an investigation compared the FB approach with the now-traditional empirical Bayesian method. It was confirmed that the FB method was superior for key ranking criteria [the posterior Poisson mean (PM) of crash frequency and potential for safety improvement] based on evaluation criteria, including sensitivity and specificity, and the sum of the PM. Next, eight ranking criteria, which included PM, posterior expected, mode and median ranks, and probability of being the worst, were proposed and evaluated for the best of several FB model variations explored. The mode rank of the posterior distribution of the Poisson mean proved to be the most promising because it tended to provide the best results, especially for top-ranked sites. The sum of the Poisson mean was also found to be a solid evaluation criterion, especially for limited numbers of top-ranked sites.