Tarko, A. P., Romero, M., Thomaz, J., Ramos, J., Sultana, A., Pineda, R., & Chen, E. (2016). Updating RoadHAT: Collision diagram builder and HSM elements (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2016/11). West Lafayette, IN: Purdue University. https://doi.org/10.5703/1288284316334
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. 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.
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. The differences between the two methods were quite limited and they could be fully reconciled if the capacity constraints was relaxed in the Indiana method and a long analysis period assumed in the HSM method.
A second major component of the study was to improve the current Indiana safety management tool, RoadHAT2, by developing a computer application facilitating preparation of a so-called collision diagram. These diagrams are an important element of safety audits. The developed application reduces this time from one or two days to an hour or less. The application also provides additional tools for analyzing and visualization of crash patterns. A developed CDB User Manual introduces the user to the tool and provides examples to help the user get familiar with the application.
road safety management, road network screening, economic evaluation, collision diagram builder
Joint Transportation Research Program
Indiana Department of Transportation
West Lafayette, Indiana
Date of this Version