Benefit-Cost Analysis of Rural Roadside Countermeasures and Evaluation of the Roadside Safety Analysis Program

Abstract

The roadside is a diverse environment having different types of objects with varying features. Roadway departure crashes can be severe and account for a majority of fatalities. In 2014, there were 17,791 fatalities (54 percent of traffic fatalities) associated with roadway departure crashes. On a rural highway, it can often be difficult for an engineer to install cost-effective countermeasures without accounting for the benefit of the potential countermeasure and the budget available. Primary objective of this thesis was to develop a series of figures to determine the cost-effective countermeasures for various considerations along the roadside of rural roads. Secondary objectives included exploration of the Roadside Safety Analysis Program (RSAP) and to examine any functionality differences between RSAP Version 2 (RSAPv2) and Version 3 (RSAPv3). Another research objective also included investigating the results of both of the versions and to provide future guidance for further exploration and development of the software. Different geometric and traffic conditions which generally exist in rural areas were selected to develop the required figures. Identical parameters were input in both versions to examine the disparities in benefit-cost ratio values and cost-effective countermeasures for each condition. Roadside countermeasures that were selected for this research were: 1. do nothing (leaving the roadway unchanged); flattening the foreslope to 1:3 (from an assumed starting condition at a 1:1 foreslope); flattening the foreslope to 1:6; and installing the guardrail. These countermeasures were tested for different geometric and traffic conditions in both the versions. A detailed literature review was performed to study the previously recommended cost-effective options on roadside and research applications of RSAP. A questionnaire survey was sent to the state departments of transportation (DOTs) to determine the practical implementation of the software and benefit-cost countermeasures in practice on rural roadsides. Installation costs were calculated for every condition and road profile combination. The program was executed in both versions keeping the same input parameters despite the different procedures in RSAPv2 and RSAPv3. Benefit-cost ratio tables from both RSAP versions were compared, and it was found that results from RSAPv2 seemed to be more consistent and acceptable for this specific area of research. Negative benefit-cost ratios were generated for flattening the foreslope in the RSAPv3 analysis, which is impractical and, therefore, benefit-cost ratios of RSAPv2 were used for further analysis. Benefit-cost ratios of selected countermeasures under different geometric and traffic conditions were tabulated and figures were developed. The developed figures are useful for local officials to determine the cost-effectiveness of potential roadside safety improvement alternatives for their specific conditions.