Development and Application of Safety Performance Functions for Illinois

摘要

This report explains the procedure involved in developing Safety Performance Functions (SPF) for the road segments and intersections in the state of Illinois, under the jurisdiction of the Illinois Department of Transportation. SPFs predict the relationship among traffic, geometric conditions of the road and crash density, crash severity, and crash type. The SPFs are developed in such a way that they can be easily incorporated into the SafetyAnalyst tool that is being developed by FHWA to analyze and improve the safety of road elements. The SPFs are used to calculate a given sites Potential for Safety Improvement (PSI) and thus help in identifying the locations that have the highest potential for improvement. A literature review was conducted as a part of the study to identify the methodology that would be needed. The literature review included studies on identifying the statistical techniques best suited for the requirement and identifying road element variables that have to be considered while developing SPFs. This report also includes the background and rationale behind the use of techniques such as Empirical Bayesian method, Sliding Window technique, and other such procedures that have been used in the analysis.