Implementing Highway Safety Manual Life-Cycle Benefit–Cost Analysis of Safety Improvements

Abstract

The Highway Safety Manual (HSM) lists four methods for determining the change in crash severity in order of reliability. The life-cycle benefit–cost analysis currently used by the Utah Department of Transportation is similar to the least reliable method. To provide a tool to perform the most reliable method defined by the HSM—the predictive method—this research developed a spreadsheet-based tool to allow department engineers to perform life-cycle benefit–cost analyses for the 11 roadway segment types included in the HSM. The tool can be used to analyze the cost-effectiveness of safety-related improvements identified by the Utah crash prediction model, which was previously developed to identify safety hot spots on the state highway system. The concept and the spreadsheet layout are presented by using the rural two-lane, two-way highway spreadsheet as an example. Then a case of a rural two-lane, two-way highway with two selected countermeasures is presented to demonstrate the use of this spreadsheet to compare their benefit–cost ratios. One important aspect associated with life-cycle benefit–cost analyses of safety-related improvements is the cost of implementing such improvements. Safety-related improvements are often included in larger construction contracts and such costs vary significantly, depending on the way they are included in the larger contracts. Hence, construction costs of safety-related improvements—such as initial cost, periodic rehabilitation cost, and annual maintenance costs—must be prepared outside this spreadsheet by the user.