Calibration of highway safety manual prediction models for Delaware intersections
Date
2024
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Publisher
University of Delaware
Abstract
There has been growing momentum across the United States to develop systematic procedures for quantifying and predicting safety in order to build up safer roadways for all users. Over the last century, highway safety-related decisions at the project level were mostly made based on engineering judgment experience and standards compliance. Published in 2010, the Highway Safety Manual (HSM) provides information and methodologies on measuring, estimating, and evaluating roadways in terms of safety. The HSM introduces techniques for predicting crashes based on predictive models developed by different researchers in different periods and from different regions using base conditions. The main goal of this research is to calculate calibration factors to account for the difference between predictive methods under base conditions and under Delaware-specific conditions. This analysis was performed collecting data mostly from the state of Delaware, Google Street View, and satellite imagery. The research utilized the software ArcGIS Pro to store data and perform spatial analysis. Calibration factors and their goodness-of-fit measures are calculated for all HSM intersection classifications (ten site types). This research also provides local crash distribution proportion tables based on injury severity level and collision type. The results suggest that calibration factors for five site types are recommended for use, and five site types are not recommended for use. In general, calibration factors were higher than 1.0, implying that the HSM predictive models underpredict reported crashes in Delaware. The study concludes with a discussion on data limitations, thoughts about HSM crash prediction methodology, and suggestions for future research.
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Keywords
Highway Safety Manual, Delaware intersections, Calibration factors, Safety performance analysis