Calibrating Crash Modification Factors for Wyoming-Specific Conditions : Application of the Highway Safety Manual - Part D

2017PDFTech ReportWY- 17/04FRS03216Highway safetyHighway factors in accidentsGeometric segmentsSnow fencesRumble stripsIntersectionsTraffic dataAccident dataHighway Safety ManualCrash Modification FactorsSafetyEffectivenessShoulder Rumble StripsPassing LanesHeadlight UseSignsIntersectionsAdding Turn LanesSnow FencesWyomingWyomingUnited StatesWyoming. Dept. of TransportationAhmed, Mohamed M.Gaweesh, SherifHossain, Md JulfikerSharmin, SadiaPeel, ThomasUniversity of Wyoming. Dept. of Civil and Architectural EngineeringWyoming Technology Transfer CenterWyoming. Dept. of TransportationUS Transportation CollectionMohamed Ahmed, Ph.D., P.E.- orcid.org/0000-0002-1921-0724; Sherif Gaweesh, M.S. - orcid.org/0000-0001-7977-6378; Md Julfiker Hossain -orcid.org/0000-0001-7173-7040; Sadia Sharmin \u2013 orcid.org/0000-0003-0947-8345; Thomas Peel \u2013 orcid.org/ 0000-0002-5357-602 This study is considered a first step towards validating the applicability of the Highway Safety Manual (HSM) Part D to Wyoming conditions. The HSM Part D provides a quantitative measure of safety for various countermeasures known as crash modification factors (CMF). These CMFs are provided for four distinct groups of treatments; roadway segments (e.g., rumble strips, passing lanes, etc.), intersections (e.g., flashing yellow arrows), special facilities (e.g., Highway-rail crossings, and interchanges), and road networks. CMFs provided in the HSM Part D are calibrated based on data collected from a few states in the US, which may not represent the same safety efficacy of countermeasures implemented in Wyoming. The objectives of this study are (1) to validate the applicability of the HSM Part D to Wyoming conditions, (2) to calibrate CMFs for various countermeasures in Wyoming, and (3) to provide recommendations in terms of data requirements, how to mitigate data shortcoming, and applicability of alternative analytical methodologies to evaluate the safety effectiveness of specific countermeasures. Depending on data availability, various observational before-after and cross-sectional techniques were adopted in this study to calibrate CMFs for six countermeasures applied to roadway segments, intersections, and special facilities. The results indicated that the majority of these countermeasures are statistically significant in reducing crash frequencies and severity