Comparison of Safety Evaluation Approaches for Intersection Signalization in Florida

摘要

In this study, we evaluate the safety effectiveness of introducing traffic signals to stop controlledintersections. According to the Highway Safety Manual (HSM), various Crash ModificationFactors (CMFs) have been identified to predict safety performance after updating a stop to asignal controlled intersection. Different CMFs may be expected for the same treatment underdifferent circumstances. Therefore, one CMF may not be able to represent the safetyperformance under all settings. This paper presents CMFs for signalization and attempts toinvestigate the relationship between CMF and Annual Average Daily Traffic (AADT). CMFsare examined at different ranges of AADT. According to the 2009 Manual on Uniform TrafficControl Devices (MUTCD), signalizing a stop controlled intersection would be expected to havepositive effects on the safety performance. This assumption needs to be proven under differentintersection configurations. Our study focuses on grouping intersections into five AADT levelsand comparing the safety performance of these levels. In addition, the effects on total crashesand severe crashes (fatal and injury crashes) are analyzed separately; two Safety PerformanceFunctions (SPFs) are estimated, one for total and the other is for fatal and injury crashes. Aftercalculating CMFs based on the Empirical Bayes (EB) method, the result points out that potentialrisk may occur when the AADT of the target intersections are between 20,000-25,000 vpd fortotal crashes and 20,000-35000 for fatal and injury (F+I) crashes. Therefore, based on this result,it is suggested that the MUTCD signalization warrant could consider AADT levels and otherconsiderations when making the signalization decision.