The Interactive Highway Safety Design Model (IHSDM) is a suite of software developed by the Federal Highway Administration (FHWA) for monitoring and analyzing two-lane rural highways in the United States. Among the six modules available in IHSDM, two were chosen for evaluation because of their applicability to audit safety of the two-lane rural highways in Utah, namely the Crash Prediction Module (CPM) and the Intersection Review Module (IRM). It was found that the CPM can produce reasonably reliable crash predictions if appropriate input data, especially alignment data, reflect the existing conditions at reasonable accuracy and engineering judgment is used. Using crash records available from the crash database developed by the Utah Department of Transportation (UDOT) and CPM’s crash prediction capability, UDOT’s traffic and safety engineers can locate “hot spots” for detailed safety audit, thus making the safety audit task more focused and effective. Unlike the CPM, the outputs of the IRM are qualitative and include primarily suggestions and recommendations. They will help the traffic and safety engineers what to look for as they visit the sites, such as a lack of stopping sight distance and a lack of passing sight distance. Based on the findings of the study, it is concluded that the CPM and IRM of IHSDM could be a useful tool for engineering decision-making during safety audits of two-lane rural highways. However, the outputs from these modules demand knowledge and experience in highway design. (Author/publisher)
Abstract