Abstract
The Interactive Highway Safety Design Model (IHSDM) is a suite of software developed by FHWA for monitoring and analyzing two-lane rural highways in the United States. IHSDM consists of six modules: Policy Review, Crash Prediction (CPM), Design Consistency, Traffic Analysis, Intersection Review, and Driver/Vehicle. Of the six modules, CPM was selected for possible use in safety audits of two-lane rural highways. Many departments of transportation (DOTs) often lack the resources to calibrate the model's factors; hence, the module was tested to see if it could be used as is, without model calibration. Three two-lane rural highway sections in Utah were selected for a sample application of CPM to safety audits. The results of this evaluation show that the CPM can produce reasonably reliable crash predictions if appropriate input data, especially alignment data, reflect existing conditions with reasonable accuracy. Using crash records available from the multiyear crash database maintained 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 and thus improve the safety audit task's focus and effectiveness. The study concludes that CPM could be useful for engineering decision making during safety audits of two-lane rural highways. Interpreting the outputs from CPM, however, requires knowledge and experience in highway design.
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