The Interactive Highway Safety Design Model (IHSDM) is a tool for assessing the safety impact of project-level design decisions by implementing the HSM crash prediction methodology. Safety Performance Functions (SPFs), Crash Modification Factors/Functions (CMFs), calibration factors, and crash proportions are utilized in predicting the number, severity, and type of crashes occurring on various types of roadway facilities. This study updated and expanded the set of CMFs applicable to Indiana conditions for various geometric, traffic, pavement, and other road characteristics. CMFs for 80 various road and control improvements for urban and rural segments, intersections, and interchanges. This report also presents the methodology of calibrating the IHSDM’s predictive components based on local data and past research. This method jointly estimates the SPFs and CMFs to preserve the crash prediction consistency. SPFs, CMFs, and crash proportions were calibrated for Indiana rural two-lane segments, rural divided multilane segments, and urban/suburban arterial segments. Example calculations showed that some results were only slightly affected while others vary considerably. This finding confirms the need for calibrating the parameters in the IHSDM to local conditions.

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road safety, IHSDM, design, CMF, CRF, SPF, HSM

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Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version