In order to minimize the losses resulting from traffic crashes, Indiana developed its road safety management methods before the Highway Safety Manual and the SafetyAnalyst became available. The considerable cost of replacing the Indiana current practice with the safety management based on the Highway Capacity Manual prompted the Indiana DOT to continue using its own safety management tools. This study includes two related but distinct components: (1) Comparison of the HSM-based and...
More DescriptionIn order to minimize the losses resulting from traffic crashes, Indiana developed its road safety management methods before the Highway Safety Manual and the SafetyAnalyst became available. The considerable cost of replacing the Indiana current practice with the safety management based on the Highway Capacity Manual prompted the Indiana DOT to continue using its own safety management tools. This study includes two related but distinct components: (1) Comparison of the HSM-based and Indiana methods of safety management, and(2) Development of a Collision Diagram Builder (CDB) to improve current Indiana safety management tools. This study concluded that the HSM SPFs would need to be calibrated to the Indiana conditions before they could be used. Calibrating the SPFs for, so-called, base conditions would lead to an insufficient number of roads and, consequently, to estimates that were not trustworthy. This problem is amplified by the large number of road categories and crash types in HSM (110 categories and 468 crash severity proportions). Furthermore, a re-calibration process must be repeated over time to keep the SPFs updated to the changes in safety. An advanced statistical simulation of a safety management system aimed to maximize the total safety benefit was performed. The results indicate that two best performing criteria: the HSM EPDO-based criterion and the Indiana total cost of crashes criterion are equivalent and they produce the same results. It is important that the HSM provides guidance as to which screening criteria support which screening objectives because some of the HSM criteria were found inadequate for maximizing the overall safety benefit. It also was concluded that although the cost of crashes and the Index of Crash Cost and Frequency used separately proved to be good screening criteria in Indiana, the combined use of these two measures did not deliver any considerable improvement. Two differences were found between the HSM and Indiana procedures for evaluating the benefits and costs of safety projects: the infinite period of analysis and the road capacity constraint on traffic growth. Consequently, Indiana results depend on the capacity constraints while the HSM results depend on the length of the analysis period.