Project-Level Life-Cycle Benefit–Cost Analysis Approach for Evaluating Highway Segment Safety Hardware Improvements

This paper presents a methodology for a benefit–cost analysis of improving the conditions of highway segment safety hardware over its life cycle. In the framework, a safety index is established for assessing the risks of vehicle crashes on a highway segment. These risks are associated with the safety-related attributes of the segment, which include traffic volume, segment length, standards and consistency of geometric design, pavement surface condition, safety hardware condition, and roadside features. The annual potential for safety improvements (PSI) associated with safety hardware improvements is calculated as reductions in fatal, injury, and property-damage-only crashes on the highway segment on the basis of the without- and with-improvement safety indices. Then, by monetizing and extrapolating the annual PSI over the longest hardware service life, the maximum life-cycle benefits of safety hardware improvements for the highway segment are established. To demonstrate the application of the methodology, data on 193 highway segments in Ozaukee County, Wisconsin, are collected and analyzed and the results are validated using the root-mean-square error test, chi-square test, Spearman's rank correlation test, and the Mann–Whitney test. A direction for future research is recommended to simplify the methodology and to prepare guidelines for enhancing its practical implementation.