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Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects (2018)

Chapter: Chapter 5. Application of Benefit-Cost Analysis for 3R Projects

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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
×
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Suggested Citation:"Chapter 5. Application of Benefit-Cost Analysis for 3R Projects." National Academies of Sciences, Engineering, and Medicine. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Washington, DC: The National Academies Press. doi: 10.17226/25206.
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47 Chapter 5. Application of Benefit-Cost Analysis for 3R Projects Benefit-cost analysis enables highway agencies to assess design alternatives for 3R projects and decide (a) whether geometric design improvements should be made as part of the project and, if so, (b) which geometric design improvements are appropriate for particular projects. 5.1 Elements of Benefit-Cost Analysis The elements of a benefit-cost analysis for a particular design alternative are presented here. Examples of the use of these elements in benefit-cost analysis are presented below. While the computations needed for a benefit-cost analysis may appear complex, they can be performed automatically by the benefit-cost analysis spreadsheet tools presented in Section 5.6. 5.1.1 Implementation Cost for Geometric Design Improvements A key element of benefit-cost analysis for a particular geometric design alternative is the cost of implementing that alternative. This cost is referred to as the implementation cost, rather than the construction cost, because it includes not only construction costs, but also the cost of acquiring any right-of-way needed to implement the design alternative. Highway agencies differ in their policies concerning right-of-way acquisition as part of 3R projects. Some agencies almost never consider design alternatives that involve right-of-way acquisition as part of 3R projects; other agencies routinely consider 3R project alternatives that involve right-of-way acquisition. The benefit-cost procedures presented here will support either approach. Utility relocation costs may be incurred in some 3R projects. Such costs are site-specific and difficult to generalize. Therefore, they have not been included in the automated cost estimation procedures incorporated in the spreadsheet tools used with these guidelines. However, users of the procedures may include utility relocation costs in site-specific project implementation costs for benefit-cost analysis, where appropriate. The cost of pavement resurfacing should not be included as part of the implementation cost for benefit-cost analysis of potential geometric design improvements considered in conjunction with 3R projects. For most 3R projects, the pavement will be resurfaced regardless of whether geometric design improvements are made, so the pavement resurfacing cost is not relevant to decisions concerning geometric design improvements and should not be included in the project implementation cost. Every highway agency has established procedures for estimating the cost of geometric design alternatives, both for cost estimates that are sufficiently accurate for planning-level analyses and for detailed cost estimates prepared in final design. It is assumed that, in most cases, highway agencies will prefer to use their own project cost estimation procedures as the basis for 3R project benefit-cost analyses. Cost estimates with planning-level accuracy are appropriate for

48 deciding whether to incorporate geometric design improvements in a 3R project and what geometric design improvements to implement. A default procedure for estimating the implementation costs of 3R improvements at specific sites is presented in Appendix A. This default cost estimation procedure is intended for application by highway agencies that want to make a quick assessment of the need for geometric improvements in a specific 3R project without the effort needed to apply their own cost estimation procedures. The unit cost values used in the default cost estimation procedure may be easily modified to reflect local conditions. The project implementation cost estimates made with the default procedure can be refined later, if appropriate, using the agency’s own project cost estimation procedures. The implementation cost for geometric design improvements may represent the cost of a single geometric design change or the combined cost of multiple geometric design changes that may potentially be made as part of the same project. The default cost estimation procedure presented in Appendix A can address either single or multiple geometric design improvements. The value of the default cost estimation procedure to highway agencies is that they can quickly determine whether geometric design alternatives should be considered at all and what the general scope of design improvement should be without going to the effort of making detailed cost estimates with their own cost estimation procedures. For example, if a benefit cost-analysis based on the default cost estimation procedure showed that the costs of design alternatives for a particular project far exceed the benefits, the effort required to make more accurate estimates of project implementation cost using the agencies own project cost estimation procedures can be avoided. The decision as to whether to use the default project cost estimation procedure or the agency’s own project cost estimation procedures can be made by each highway agency that uses these guidelines. 5.1.2 3R Project Crash Frequency and Severity Reduction Benefits The benefits of 3R projects are being estimated with a combination of the following elements:  Expected crash frequency by crash severity level for the existing highway if no geometric design improvements are made based on the HSM Part C predictive methods. The agency may choose to base the benefit-cost analysis on the predicted crash frequency from the HSM Part C predictive method or, when site-specific crash history data are available, to combine the predicted and observed crash frequencies using the empirical Bayes (EB) procedure presented in the Appendix to HSM Part C.  Expected reduction in crash frequency due to project implementation based on CMFs for specific countermeasures from the HSM and other sources.  Crash cost savings per crash reduced by severity level.

49  Improvement service life, which is typically assumed to be 20 years (see below), except that a shorter service life should be used for striping and delineation and rumble strips. Each of these issues is addressed in more detail below. 5.1.3 Expected Crash Frequency by Crash Severity Level If No Geometric Design Improvements are Made This section summarizes the crash prediction methodology from HSM Part C (2), as applied to rural two-lane highways (see HSM Chapter 10), rural multilane highways (see HSM Chapter 11), and urban and suburban arterials (see HSM Chapter 12). Full details of these procedures are provided in the HSM. 5.1.3.1 Roadway Segments on Rural Two-Lane Highways The HSM Chapter 10 crash prediction model for roadway segments on rural two-lane highways has the following functional form (2): AADT L 365 10 e . C CMF CMF … CMF / (26) where: Npredicted ravg = predicted annual average crash frequency for a particular road segment averaged over the improvement service life AADTy = annual average daily traffic volume for year y of the improvement service life (veh/day) n = improvement service life (years) L = length of roadway segment (mi) Cr = calibration factor for roadway segments of a particular type developed for a particular jurisdiction or geographical area CMF1r … CMFnr = applicable crash modification factors (see HSM Part C) Equation (26) provides the predicted frequency for total crashes. Values presented in HSM Table 10-3 are used to break this total down for specific severity levels. 5.1.3.2 Roadway Segments on Rural Multilane Highways The HSM Chapter 11 crash prediction model for roadway segments on rural multilane highways has the following functional form (2):

50 C CMF CMF … CMF / (27) where: a,b = coefficients presented in HSM Chapter 11 In the HSM Chapter 11 procedure, Equation (27) is applied separately for crashes by severity level. The values of coefficients a and b in Equation (27) are presented in HSM Table 11-3 for rural multilane undivided roadway segments and in HSM Table 11-5 for rural multilane divided roadway segments. The CMFs used in Equation (27) also differ between rural multilane undivided and divided roadway segments. 5.1.3.3 Roadway Segments on Urban and Suburban Arterial Roadway Segments The HSM Chapter 12 crash prediction model for roadway segments on urban and suburban arterials is a combination of three terms (2): ∑ C / (28) where: Nbr = predicted average crash frequency for an individual roadway segment averaged over the improvement service life (including multiple-vehicle nondriveway crashes, single-vehicle crashes, and multiple-vehicle driveway crashes) Npedr = predicted average crash frequency of vehicle-pedestrian crashes for an individual roadway segment averaged over the improvement service life Nbiker = predicted average crash frequency of vehicle-bicycle crashes for an individual roadway segment averaged over the improvement service life Equation (28) provides the predicted frequency for crashes separately by severity level. Nbr is a combination of separate models for multiple-vehicle nondriveway crashes, single-vehicle crashes, and multiple-vehicle driveway crashes. The models for multiple-vehicle nondriveway crashes and single-vehicle crashes each incorporate applicable CMFs. The details of the models used for each term in Equation (28) are presented in HSM Chapter 12. 5.1.3.4 At-Grade Intersections The predictive models for at-grade intersections on all facility types have the following general form (2): ∑ , , … / (29)

51 where: Npredicted iavg = predicted average crash frequency for a particular intersection for a particular year a,b,c = coefficients presented in HSM Chapter 10, 11, and 12 AADTy,maj = annual average daily traffic volume on the major road (veh/day) AADTy,min = annual average daily traffic volume on the minor road (veh/day) Ci = calibration factor for intersections of a particular type developed for a particular jurisdiction or geographical area CMF1i … CMFni = applicable crash modification factors (see HSM Part C) The values for coefficients a, b, and c are presented in the HSM as follows:  in HSM Equations (10-8) through (10-10) for intersections on rural two-lane highways  in HSM Tables 11-7 and 11-8 for intersections on rural multilane highways  in HSM Tables 12-10 and 12-12 for intersections on urban and suburban arterials For intersections on urban and suburban arterials, Equation (29) is applied separately for multiple- and single-vehicle collisions. 5.1.3.5 Combining Predicted and Observed Crash Frequencies Many highway agencies may prefer to take a systemic approach and make risk-based decisions on the need for geometric design improvements in 3R projects based on predicted crash frequencies from the HSM alone. However, observed crash history data can also be considered in analyses for individual sites using the EB procedure presented in the Appendix to HSM Part C (2). This procedure determines a weighted-average crash frequency using the following procedure: 1 (30)   years studyall predictedNk1 1w (31) where: Nexpected = estimate of expected average crash frequency for the crash data period Npredicted = predictive model estimate of average crash frequency predicted for the crash data period under the given conditions (Npredicted ravg or Npredicted iavg) Nobserved = observed crash frequency at the site over the study period w = weighted adjustment to be placed on the predictive model estimate k = overdispersion parameter of the associated SPF used to estimate Npredicted

52 Values for the overdispersion parameter, k, can be determined from:  HSM Equation (10-7) for roadway segments on rural two-lane highways  Text accompanying HSM Equations (10-8) through (10-10) for intersections on rural two-lane highways  HSM Equation (11-8) and Tables 11-3 and 11-5 for rural multilane highways  HSM Tables 11-7 and 11-8 for intersections on rural multilane highways  HSM Tables 12-3 and 12-5 for roadway segments on urban and suburban arterials  HSM Tables 12-10 and 12-12 for intersections on urban and suburban arterials The EB procedure is implemented by applying the applicable predictive model [i.e. Equation (26), (27), (28), or (29)] to the past period for which observed crash data are available rather than to the future period over which the improvement will be in service. Equations (30) and (31) are then applied to combine the predicted and observed crash frequencies for the crash data period. Finally, the expected crash frequency determined with Equations (30) and (31) is updated to future years as follows: , , (32) where: Nexpected,y = expected average crash frequency for year y Npredicted,y = predicted average crash frequency for year y 5.1.4 Expected Reduction in Crash Frequency for Specific Design Alternatives The expected reduction in crash frequency for specific candidate design alternatives can be determined by applying the CMFs presented in Section 4.3 of these guidelines. The expected reduction in crash frequency for a specific crash severity level resulting from implementation of a a particular design alternative at a particular site can be determined as: 1 (33) where: CRmjk = expected reduction in crash frequency for crash severity level k resulting from implementation of improvement j at site m CMFjk = crash modification factor for crash severity level k from implementing improvement j Nmk = expected annual crash frequency for crash severity level k at site m prior to improvement Nmk represents the value of Npredicted or Nexpected derived in Section 5.1.3.

53 The CMF representing the effectiveness of a single geometric design improvement is determined as: , , (34) where: CMFj,after = crash modification factor for improvement j in the condition after improvement CMFj,before = crash modification factor for improvement j in the condition before improvement The CMF representing the combined effectiveness for a design alternative that incorporates several geometric design improvements is determined as: , , , , … , , (35) 5.1.5 Crash Costs by Crash Severity Level Each highway agency has its own policy concerning the estimated cost savings of reducing crashes of specific severity levels used in benefit-cost analyses. These estimates vary widely based on the assumptions made in developing those estimates. Some agencies rely on estimates of the societal costs of crashes, while others are based on an approach that assesses an individual’s willingness to pay for injury avoidance. Until a national consensus is reached on the appropriate method for estimating crash costs, each highway agency should follow its own policy concerning the appropriate crash cost values for use in benefit-cost analyses. If a highway agency has no specific policy on crash costs for use in benefit-cost analyses, the values in Table 25, which have been updated from those presented in the HSM and represent comprehensive societal costs of crashes, are recommended as default values: Table 25. Comprehensive Societal Costs of Crashes Updated from the Values Recommended in the HSM Crash Severity Level Comprehensive Societal Crash Costs Fatal (K) $5,722,300 Disabling Injury (A) 302,900 Evident Injury (B) 110,700 Possible Injury (C) 62,400 Property Damage Only (O) 10,100 NOTE: Updated from HSM Table 7-1 as shown in Appendix C. The methodology used to update the crash cost values presented in Table 25 is documented in Appendix C.

54 5.1.6 Improvement Service Life Pavement resurfacing typically has a service life of 7 to 12 years, depending upon construction and material quality and traffic volume, until resurfacing is needed again. However, the service life for the pavement surface does not typically enter directly into benefit-cost analyses concerning geometric design improvements, because the pavement will require resurfacing at the same interval whether geometric design improvements are incorporated in a 3R project or not. Thus, the interval between pavement resurfacing projects should not typically be a factor in determining the service life for potential geometric design improvements. Geometric design improvements such as widening of the roadway cross section, changing the road alignment, improving the roadside, or improving an intersection are essentially permanent in nature (i.e., they remain in place through future pavement resurfacing). However, they may have a functional life shorter than their physical life because future development or traffic growth may create a need for further improvements. The recommended improvement service life for improvements that involve physical changes to the roadway cross section, the roadway alignment, the roadside, or intersections is 20 years. The recommended improvement service life for rumble strips and striping and delineation improvements (particularly those that use durable pavement markings) is 5 years. However, highway agencies may use other values of improvement service life based on their own policies and experience. 5.1.7 Discount Rate or Minimum Attractive Rate of Return A discount rate or minimum attractive rate of return of 7 percent has been used in the benefit- cost analysis, in accordance with the higher value of the discount rates recommended in current Federal guidelines (29). The discount rate or minimum attractive rate of return is used in computing the present value of implementation costs and safety benefits (see below). 5.1.8 Present Value of Implementation Costs and Safety Benefits The present value of the implementation costs and safety benefits must be calculated to obtain a benefit-cost ratio. For implementation costs, the present value must be found only if the improvement is to be repeated in the future (such as striping and delineation which may be repeated several times during the service life of a geometric design improvement). In this case, the present value is computed by multiplying the future implementation cost by the single payment present worth factor:

55 P/F, %, 1 100 (36) where: (P/F, i%, n) = single payment present worth factor i = discount rate or minimum attractive rate of return (in decimal form); i.e., 7 percent is expressed as 0.07 n = number of years into the future when the improvement will be performed The present values for each future improvement are then summed to determine the total present value. Safety benefits are annual crash cost savings. To calculate the present value of safety benefits, the annual crash cost savings are multiplied by the uniform series present worth factor: P/A, %, 1 100 1 /100 1 100 (37) where: (P/A, i%, n) = uniform series present worth factor i = discount rate or minimum attractive rate of return (in decimal form); i.e., 7 percent is expressed as 0.07 n = improvement service life (years) 5.1.9 Benefit-Cost Ratio The benefit-cost ratio for a geometric design alternative in a 3R project is computed as: B/C ⁄ , %, / ⁄ , %, (38) where: B/C = benefit-cost ratio Ck = benefit ($) per crash reduced for crash severity level k ICij = implementation cost ($) for improvement j at site i Only design alternatives with benefit-cost ratios that exceed 1.0 are considered cost-effective. Highway agencies seeking to enhance the effectiveness of the safety improvement investments may choose to seek benefit-cost ratios of 2.0 or higher. 5.1.10 Net Benefit The benefit-cost ratio by itself does not provide a complete picture of the magnitude of difference between the safety benefits and implementation costs for a design alternative in a 3R

56 project. The net benefit (also referred to as net present value) is the difference between the present value of safety benefits and present value of implementation costs. NB ⁄ , %, ⁄ , %, (39) where: NB = net benefit The net benefit is often the most useful form of benefit-cost analysis results for identifying the design alternative that will maximize the safety benefits for any given level of expenditure on geometric design improvements in 3R projects. 5.2 Computational Examples of Benefit-Cost Analysis This section and Section 5.3 present examples to illustrate the interpretation of benefit-cost analysis results. These examples suggest how benefit-cost analysis can be used in the design guidelines presented in Chapter 6. If improvement costs and crash costs were consistent throughout the U.S., these examples might serve as a basis for 3R design policy. However, since the values used for improvement costs and crash costs vary widely from agency to agency, these examples in their current form should not be used as a basis for policy. Rather, benefit-cost analyses analogous to these examples, but based on site-specific or agency-specific data, should serve as a decision-making tool for choosing among 3R project design alternatives. 5.2.1 Estimating 3R Project Implementation Costs The cost estimation procedure shown in Appendix A is used to calculate the cost of a hypothetical 3R project in which the lane width on a section of roadway is widened from 10 to 12 ft. Table 26 in the following section presents roadway geometric information needed to estimate the implementation cost in this example. Unit costs for all elements of the cost estimation are presented in Appendix A. The total cost of the 3R project is determined to be $850,551. This cost however should be modified to exclude costs associated with milling and resurfacing of the existing traveled way. The benefit-cost analysis is only concerned with the costs resulting from the geometric improvement, which is lane widening in this example. The modified total implementation cost is $475,889. 5.2.2 Computational Example of Quantifying Safety Benefits for a 3R Design Alternative Section 5.1 presents the methodology for quantifying safety benefits with and without using observed crash data. In the following example, the annual safety benefit will be calculated for a roadway segment undergoing lane widening as part of a 3R project. Table 26 shows segment characteristics, which will be used in this example.

57 Table 26. Input Data for Safety Benefits Calculation Example Geometric Improvement Lane Widening from 10 to 12 ft Lane Widening Service Life 20 yrs Discount Rate 7% Roadway Type Rural Two-lane Highway Shoulder Width 2 ft Shoulder Type Paved Roadside Slope 1V:3H Centerline Rumble Strip No Shoulder Rumble Strip No Section Length 3 mi AADT (does not change) 1,000 veh/day Terrain Level Percent of Section Length on Curves 20% Typical Curve Radius 2,000 ft Number of Curves on Section 5 Presence of Spiral Transitions Yes Crash History Period 5 yrs Total Fatal-and-Injury Crashes 2 Total Property-Damage-Only Crashes 5 First, the predicted annual average crash frequency, Npredicted ravg, is calculated using Equation (26) for the existing roadway prior to the 3R project. Since the AADT does not change over time in this example, the equation simplifies to not having a summation. Using the HSM and data from Table 26, CMFs are calculated for use in determining Npredicted ravg. To determine the CMF for a rural two-lane highway with 10-ft lane width, use Table 3. Since the AADT of the roadway section is between 400 and 2,000 veh/day, an equation is used to calculate the CMFra: , , 1.05 2.81 10 400 (40) , , 1.05 2.81 10 1000 400 1.13 (41) CMFra applies only to single-vehicle run-off-the-road and multiple-vehicle head-on, opposite- direction sideswipe, and same-direction sideswipe crashes. Equation (3) is used to convert CMFra to a CMF for total crashes. For this example pra is 0.574, the default value given in the HSM. , , 1.13 1.0 0.574 1.0 1.07 (42) Other CMFs that are calculated for this example are shown in Table 27. Table 27. CMFs for Example Roadway Section Roadway Feature CMF Shoulder Width 1.09 Horizontal Curve 1.01 Roadside Slope 1.00 Centerline Rumble Strip 1.00 Shoulder Rumble Strip 1.00

58 AADT L 365 10 e . C CMF CMF … CMF / (43) AADT L 365 10 e . C CMF CMF … CMF (44) 1000 3 365 10 e . 1.00 1.07 1.09 1.01 1.00 1.00 1.00 0.942 / (45) The predicted annual average crash frequency for the roadway prior to the 3R project is 0.942 crashes per year, as shown in Equations (43) through (45). Since the lane width is being modified as part of the 3R project, the CMF for the change in lane widths must be calculated using Equation (34). To do this, the CMF for a lane width of 12 ft must first be calculated using the same procedure shown above for determining the CMF of a 10-ft lane. Table 3 shows that the CMF for 12-ft lanes is 1.00 regardless of AADT. , → , , (46) , → 1.00 1.07 0.934 (47) The CMF for increasing lane width from 10 to 12 ft is 0.93, which is calculated in Equations (46) and (47). At this point in the process of calculating the annual safety benefits, it must be decided whether to use observed crash data in the calculation of CRmjk, the expected reduction in crash frequency. For the purpose of this example, both methods will be used. 5.2.2.1 Observed Crash Data Unavailable If observed crash data are unavailable, or not to be used in the analysis, the expected annual crash reduction is computed, as shown in Equation (48) through (50). 1 (48) 1 , → (49) 1 0.934 0.942 0.062 (50)

59 5.2.2.2 Using Observed Crash Data The EB methodology, described in Section 5.1.3.5 is used to incorporate observed crash data into the calculation of the expected reduction in crash frequency. The overdispersion factor, k, is 0.236 divided by the section length, which correlates with the safety performance function for predicting crash frequency on rural two-lane roadways. Using the equations shown in Section 5.1.3.5 the expected crash frequency is calculated in Equations (51) through (54). The total crash reduction per year is calculated in Equations (55) through (57). 1 1 ∑ (51) 1 1 0.2363 0.942 5 0.730 (52) 1 (53) 0.730 0.942 5 1 0.730 5 2 5.33 5 1.065 / (54) 1 (55) 1 , → (56) 1 0.934 1.065 0.071 (57) 5.2.2.3 Calculate Present Value of Safety Benefit To this point in the example, the total crash reduction per year has been calculated with and without the use of observed crash history. The present value of the safety benefit in this example is calculated using Equation (58). Equation (58) is the numerator of Equation (38). B ⁄ , %, (58) Equation (58) can be broken into three components: (a) CRmjk, crash reduction by severity level; (b) Ck, crash cost by severity level; and (c) the uniform series present worth factor. Default crash severity distributions from HSM Chapter 10 are used to transform total annual crash reduction into annual crash reduction by severity level in Table 28.

60 Table 28. Annual Crash Reduction by Severity Level Calculation Crash Severity Level Proportion of Total Crashes CRtotal per year, Observed Crash History Known CRtotal per year, Observed Crash History Unknown CRk, Observed Crash History Known CRk, Observed Crash History Unknown K 0.013 0.071 0.062 0.000923 0.000806 A 0.054 0.071 0.062 0.00383 0.00335 B 0.109 0.071 0.062 0.00774 0.00676 C 0.145 0.071 0.062 0.0103 0.00899 O 0.679 0.071 0.062 0.0482 0.0421 The crash cost by severity level is shown in Table 25. The uniform series present worth factor is needed to transform the annual crash reduction benefit into present crash reduction benefit over the entire service life of the improvement. This is calculated in Equations (59) and (60). P/A, %, 1 100 1 /100 1 100 (59) P/A, %, 1 7 100 1 7/100 1 7100 10.5940 (60) Equations (61) and (62) shows the computation of the present value of the safety benefit. For the purposes of this example, only the expected crash reduction by severity level where the observed crash history is unknown is used in the calculation of the present value of the safety benefit. B ⁄ , %, (61) B 0.000806 ∗ 4008900 0.00335 ∗ 216000 0.00676 ∗ 79000 0.00899 ∗ 44900 0.0421 ∗ 7400 10.5940 $56,041 (62) 5.2.3 Computational Example of Benefit-Cost Analysis The implementation cost of widening the roadway section in this example is $475,889, which was discussed in Section 5.2.1. There is no need to convert this implementation cost to a present value, because the cost of the 3R project occurs in the present. No future improvements will be made during the 20-yr service life. The present value of the safety benefit is $56,041, which was calculated in Section 5.2.2. The benefit-cost ratio of widening the example roadway section can now be computed, which is shown in Equation (63).

61 / , → $56,041$475,889 0.12 (63) 5.3 Interpreting Benefit-Cost Analysis Results Further examples of benefit-cost analysis results are presented here to illustrate how analyses to assess design alternatives can be conducted and how the results of such analyses should be interpreted. 5.3.1 Example of Benefit-Cost Analysis for a Specific Project Alternative This example of a benefit-cost analysis uses the results derived in Section 5.2 to address the cost- effectiveness of widening lanes from 10 to 12 ft for a rural two-lane highway in level terrain with 2-ft paved shoulders, 1V:3H roadside foreslopes, and flexible pavement. The section of roadway considered in this example is 3 mi in length with an AADT of 1,000 veh/day. The roadway section contains modest horizontal curvature (20 percent of section length consists of horizontal curves with a typical curve radius of 2,000 ft). The safety performance of the roadway before and after widening is estimated using the HSM Chapter 10 procedures and the implementation cost for widening is based on the cost estimation procedures contained in Spreadsheet Tool 1 which is presented in detail in Appendix A. The present value of the net implementation cost for this example is $475,889 (see Section 5.2.1). The net implementation cost does not include the milling and resurfacing costs for the existing traveled way with 10-ft lanes, since these costs would be incurred by the highway agency regardless of whether the lanes are widened. The annual safety benefit of widening the lanes from 10 to 12 ft for a rural two-lane highway in this example is $5,290 (see Section 5.2.2). Assuming a discount rate of 7 percent and a service life of 20 years, the present value of the safety benefit is calculated using Equations (61) and (62), as $56,041. The benefit- cost ratio is then calculated as follows: / → , $56,041$475,889 0.12 (64) The benefit-cost ratio is 0.12, meaning that the lane widening is not economically justifiable for this roadway section. Widening the lanes from 10 to 12 ft in this 3R project would not be a desirable investment of scarce resources, unless the roadway had an existing crash pattern that is potentially correctable by widening or the level of service (LOS) was less than the highway agency’s target LOS for this roadway and widening the lanes would help to meet that target. Absent these concerns, the funds that would be needed to widen the lanes on this roadway ($475,889) would be better invested on another roadway where the safety benefits would be higher. Consider, for example, a similar site, identical in most respects to the previous example, but with an AADT of 4,000 veh/day. In this case, the net implementation cost remains the same at

62 $475,889. However, the annual safety benefit would increase to $54,641, resulting in a present value of safety benefits equal to $578,871. The benefit-cost ratio for widening lanes from 10 to 12 ft would be: / → , $578,871$475,889 1.22 (65) This example illustrates that the difference in AADT between 1,000 to 4,000 veh/day results in lane widening being economically justifiable. Lane widening for the roadway with the AADT of 4,000 veh/day would be a much better investment in safety improvement than lane widening for the roadway with an AADT of 1,000 veh/day. 5.3.2 Example of Benefit-Cost Analysis to Establish Minimum Traffic Volume Levels for Improvement Alternatives As the examples in Section 5.3.1 demonstrate, benefit-cost analysis can serve as a tool for assessing the cost-effectiveness of geometric design improvements for specific projects. These examples also suggest that benefit-cost analysis can serve as a tool to establish minimum AADT threshold for specific improvement types. Site-specific benefit-cost analyses are the more desirable approach, because they can consider both site-specific cost and benefit estimates. However, where site-specific benefit-cost analyses are not feasible, development of minimum AADT thresholds for specific improvement types may provide useful guidance to highway agencies in making 3R project design decisions. Such minimum AADT thresholds are most applicable to sites that represent average implementation costs for a particular highway agency and terrain type. Because unit construction costs, typical right-of-way costs, and crash cost values vary from agency to agency, the following tables should be considered as examples and not as a basis for design policy. Table 29 presents the results of benefit-cost calculations for widening lanes from 10 to 12 ft in level terrain on a rural two-lane highway. This example is based on the same assumptions as the examples presented in Section 5.3.1 Indeed, the lines in the table for AADTs of 1,000 and 4,000 veh/day are the results of the two computational examples shown in the previous section. Table 29 shows that the minimum AADT levels that would provide benefit-cost ratios of at least 1.0 and 2.0 for widening lanes from 10 to 12 ft are 4,000 and 7,000 veh/day respectively.

63 Table 29. Example of Benefit-Cost Calculations for Lane Widening from 10 to 12 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost Ratio Before After 10 12 1,000 475,889 56,041 0.17 10 12 2,000 475,889 289,265 0.61 10 12 3,000 475,889 434,153 0.91 10 12 4,000 475,889 578,871 1.22 10 12 5,000 475,889 723,589 1.52 10 12 6,000 475,889 868,306 1.82 10 12 7,000 475,889 1,013,024 2.13 10 12 8,000 475,889 1,157,742 2.43 10 12 9,000 475,889 1,302,459 2.74 10 12 10,000 475,889 1,447,177 3.04 NOTE: Assumed conditions – 2-ft paved shoulders; 1V:3H roadside foreslopes; flexible pavement. This analysis can be repeated for determining minimum traffic volume levels in which lane widening of other intervals becomes economically feasible. Using the same roadway section characteristics of the previous examples, benefit-cost ratios for widening lanes of different widths can be calculated at several AADT levels using the same procedures. Tables 30 through 34 show the results. Table 30. Example of Benefit-Cost Calculations for Lane Widening from 9 to 10 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost Ratio Before After 9 10 1,000 380,941 41,964 0.11 9 10 2,000 380,941 192,458 0.50 9 10 3,000 380,941 289,435 0.76 9 10 4,000 380,941 385,914 1.01 9 10 5,000 380,941 482,392 1.27 9 10 6,000 380,941 578,871 1.52 9 10 7,000 380,941 675,349 1.77 9 10 8,000 380,941 771,828 2.03 9 10 9,000 380,941 868,306 2.28 9 10 10,000 380,941 964,785 2.53 NOTE: Assumed conditions – 2-ft paved shoulder; 1V:3H roadside foreslopes; flexible pavement.

64 Table 31. Example of Benefit-Cost Calculations for Lane Widening from 9 to 11 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost RatioBefore After 9 11 1,000 475,889 86,797 0.18 9 11 2,000 475,889 433,512 0.91 9 11 3,000 475,889 651,230 1.37 9 11 4,000 475,889 868,306 1.82 9 11 5,000 475,889 1,085,383 2.28 9 11 6,000 475,889 1,302,459 2.74 9 11 7,000 475,889 1,519,536 3.19 9 11 8,000 475,889 1,736,613 3.65 9 11 9,000 475,889 1,953,689 4.10 9 11 10,000 475,889 2,170,766 4.56 NOTE: Assumed conditions – 2-ft paved shoulders; 1V:3H roadside foreslopes; flexible pavement. Table 32. Example of Benefit-Cost Calculations for Lane Widening from 9 to 12 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost RatioBefore After 9 12 1,000 570,837 98,005 0.17 9 12 2,000 570,837 481,723 0.84 9 12 3,000 570,837 723,589 1.27 9 12 4,000 570,837 964,785 1.69 9 12 5,000 570,837 1,205,981 2.11 9 12 6,000 570,837 1,447,177 2.54 9 12 7,000 570,837 1,688,373 2.96 9 12 8,000 570,837 1,929,570 3.38 9 12 9,000 570,837 2,170,766 3.80 9 12 10,000 570,837 2,411,962 4.22 NOTE: Assumed conditions – 2-ft paved shoulders; 1V:3H roadside foreslopes; flexible pavement. Table 33. Example of Benefit-Cost Calculations for Lane Widening from 10 to 11 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost RatioBefore After 10 11 1,000 380,941 44,833 0.12 10 11 2,000 380,941 241,054 0.63 10 11 3,000 380,941 361,794 0.95 10 11 4,000 380,941 482,392 1.27 10 11 5,000 380,941 602,990 1.58 10 11 6,000 380,941 723,589 1.90 10 11 7,000 380,941 844,187 2.22 10 11 8,000 380,941 964,785 2.53 10 11 9,000 380,941 1,085,682 2.85 10 11 10,000 380,941 1,205,981 3.17 NOTE: Assumed conditions – 2-ft paved shoulders; 1V:3H roadside foreslopes; flexible pavement.

65 Table 34. Example of Benefit-Cost Calculations for Lane Widening from 11 to 12 ft in Level Terrain on a Rural Two-Lane Highway Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost Ratio Before After 11 12 1,000 380,941 11,208 0.03 11 12 2,000 380,941 48,211 0.13 11 12 3,000 380,941 72,359 0.19 11 12 4,000 380,941 96,478 0.25 11 12 5,000 380,941 120,598 0.32 11 12 6,000 380,941 144,718 0.38 11 12 7,000 380,941 168,837 0.44 11 12 8,000 380,941 192,957 0.51 11 12 9,000 380,941 217,077 0.57 11 12 10,000 380,941 241,196 0.63 11 12 11,000 380,941 265,316 0.70 11 12 12,000 380,941 289,435 0.76 11 12 13,000 380,941 313,555 0.82 11 12 14,000 380,941 337,675 0.89 11 12 15,000 380,941 361,794 0.95 11 12 16,000 380,941 385,914 1.01 11 12 17,000 380,941 410,034 1.08 11 12 18,000 380,941 434,153 1.14 11 12 19,000 380,941 458,273 1.20 11 12 20,000 380,941 482,392 1.27 NOTE: Assumed conditions – 2-ft paved shoulders; 1V:3H roadside foreslopes; flexible pavement. 5.4 Using Benefit-Cost Analysis to Establish Minimum AADT Guidelines for 3R Improvements The cost-effectiveness of any specific design alternative for a 3R project can be assessed in a benefit-cost analysis analogous to that shown in any line of Tables 29 through 34. However, benefit-cost analysis has a further advantage in that it can be used to identify which of multiple design alternatives for a 3R project would be most cost-effective. This type of analysis is referred to as incremental benefit-cost analysis. Incremental benefit-cost analysis assesses whether each additional expenditure in implementation cost provides an added net benefit. The simplest method for performing an incremental benefit-cost analysis is to determine the net benefit (present value of safety benefits minus implementation cost) for each design alternative and select the design alternative with the highest net benefit, as long as that highest net benefit is also greater than zero. The example in Table 35 shows an incremental benefit-cost analysis for lane widening for an existing rural two-lane highway with 9-ft lanes in level terrain. The implementation cost, safety benefit, and benefit-cost ratio shown in Table 35 for lane widening from 9 to 10 ft, 9 to 11 ft, and 9 to 12 ft are those shown in Tables 30, 31, and 32, respectively. In each case, the net benefit has also been added. Table 35 shows the following results for roadways with existing 9-ft lanes:

66  for a roadway with an AADT of 1,000 veh/day, none of the lane widening alternatives are cost-effective  for a roadway with an AADT of 2,000 or 3,000 veh/day, lane widening from 9 to 11 ft has the maximum net benefit. While lane widening from 9 to 12 ft is cost-effective, its net benefit is less than the net benefit of widening from 9 to 11 ft, and therefore the additional increment of investment to widen to 12-ft lanes is not cost-effective  for a roadway with an AADT of 4,000 veh/day or more, widening from 9 to 12 ft has the highest net benefit in all cases Table 36 shows a similar analysis for lane widening for an existing two-lane highway with 10-ft lanes in level terrain which indicates that:  for a roadway with an AADT of 3,000 veh/day or less, none of the lane widening alternatives are cost-effective  for a roadway with an AADT of 4,000 veh/day, the alternatives of lane widening from 10 to 11 ft and from 10 to 12 ft are nearly equal in net benefits, although widening from 10 to 12 ft is slightly higher  for a roadway with an AADT of 5,000 veh/day or more, widening from 10 to 12 ft has the highest net benefit in all cases For an existing two-lane highway with 11-ft lanes in level terrain, there is only one alternative to be considered (lane widening from 11 to 12 ft), so no incremental analysis is needed. Table 34 addresses this situation, indicating that lane widening from 11 to 12 ft only becomes cost- effective for roadways with AADT of 16,000 veh/day or more. Thus, lane widening in 3R projects on most existing rural two-lane highways with 11-ft lanes is not a desirable safety investment. The reason for this result is that the HSM Chapter 10 procedures show very little difference in crash frequency between 11- and 12-ft lanes on rural two-lane highways (see Figure 2). The results of the incremental benefit-cost analyses presented above show that benefit-cost analyses can be used to create guidelines on the minimum AADT levels for which lane widening or other geometric design improvements may be cost-effective in 3R projects. Further examples of using benefit-cost analysis to establish 3R design guidelines using minimum AADT levels are presented in the next section. Tables 29 to 34 show that the minimum AADT levels that would provide benefit-cost ratios of at least 1.0 and 2.0 for each widening scenarios are as follows: Lane Widening Scenario Minimum AADT (veh/day) for B/C=1.0 B/C=2.0 Widen from 9 to 10 ft 4,000 8,000 Widen from 9 to 11 ft 3,000 5,000 Widen from 9 to 12 ft 3,000 5,000 Widen from 10 to 11 ft 4,000 7,000 Widen from 10 to 12 ft 4,000 7,000 Widen from 11 to 12 ft 16,000 32,000

67 Table 35. Example of Incremental Analysis to Determine Net Benefits of Lane Widening for Existing Rural Two-Lane Highways with 9-ft Lanes in Level Terrain AADT (veh/day) Lane Widening from 9 to 10 ft Lane Widening from 9 to 11 ft Lane Widening from 9 to 12 ft Implementation Cost ($) Crash Reduction Benefit ($) B-C Ratio Net Benefit ($) Implementation Cost ($) Crash Reduction Benefit ($) B-C Ratio Net Benefit ($) Implementation Cost ($) Crash Reduction Benefit ($) B-C Ratio Net Benefit ($) 1,000 380,941 41,964 0.11 -338,977 475,889 86,797 0.18 -389,092 570,837 98,005 0.17 -472,832 2,000 380,941 192,458 0.5 -188,483 475,889 433,512 0.91 -42,377 570,837 481,723 0.84 -89,114 3,000 380,941 289,435 0.76 -91,506 475,889 651,230 1.37 175,341 570,837 723,589 1.27 152,752 4,000 380,941 385,914 1.01 4,973 475,889 868,306 1.82 392,417 570,837 964,785 1.69 393,948 5,000 380,941 482,392 1.27 101,451 475,889 1,085,383 2.28 609,494 570,837 1,205,981 2.11 635,144 6,000 380,941 578,871 1.52 197,930 475,889 1,302,459 2.74 826,570 570,837 1,447,177 2.54 876,340 7,000 380,941 675,349 1.77 294,408 475,889 1,519,536 3.19 1,043,647 570,837 1,688,373 2.96 1,117,536 8,000 380,941 771,828 2.03 390,887 475,889 1,736,613 3.65 1,260,724 570,837 1,929,570 3.38 1,358,733 9,000 380,941 868,306 2.28 487,365 475,889 1,953,689 4.1 1,477,800 570,837 2,170,766 3.8 1,599,929 10,000 380,941 964,785 2.53 583,844 475,889 2,170,766 4.56 1,694,877 570,837 2,411,962 4.22 1,841,125 NOTE: Based on conditions evaluated in Tables 29 through 34. Table 36. Examples of Incremental Analysis to Determine Net Benefits of Lane Widening for Existing Rural Two-Lane Highways with 10-ft Lanes in Level Terrain AADT (veh/day) Lane Widening from 10 to 11 ft Lane Widening from 10 to 12 ft Implementation Cost ($) Crash Reduction Benefit ($) B-C Ratio Net Benefit ($) Implementation Cost ($) Crash Reduction Benefit ($) B-C Ratio Net Benefit ($) 1,000 380,941 44,833 0.12 -336,108 475,889 56,041 0.17 -419,848 2,000 380,941 241,054 0.63 -139,887 475,889 289,265 0.61 -186,624 3,000 380,941 361,794 0.95 -19,147 475,889 434,153 0.91 -41,736 4,000 380,941 482,392 1.27 101,451 475,889 578,871 1.22 102,982 5,000 380,941 602,990 1.58 222,049 475,889 723,589 1.52 247,700 6,000 380,941 723,589 1.9 342,648 475,889 868,306 1.82 392,417 7,000 380,941 844,187 2.22 463,246 475,889 1,013,024 2.13 537,135 8,000 380,941 964,785 2.53 583,844 475,889 1,157,742 2.43 681,853 9,000 380,941 102,452 2.85 -278,489 475,889 1,302,459 2.74 826,570 10,000 380,941 1,205,981 3.17 825,040 475,889 1,447,177 3.04 971,288 NOTE: Based on conditions evaluated in Tables 29 through 34.

68 The high values for minimum AADT level for widening from 11 to 12 ft occur because there is relatively little safety benefit in widening lanes from 11 to 12 ft on a rural two-lane highway (see Figure 3). The minimum AADT levels for lane widening can be expanded to include rolling and mountainous terrain types, as shown in Table 37. Minimum AADT levels can be established for shoulder widening using the same procedure described above, as shown in Table 38. Table 37. Example of AADT Levels at which Lane Widening Becomes Cost-Effective Rural Two-Lane Highway Segments Assuming 2-ft Paved Shoulders, 1V:3H Roadside Foreslopes, and Moderate Horizontal Curvature Proposed Improvement Minimum AADT level (veh/day) for benefit-cost ratio = 1.0 Minimum AADT level (veh/day) for benefit-cost ratio = 2.0 Level Rolling Mountainous Level Rolling Mountainous Widen from 9 to 10 ft 4,000 5,000 7,000 8,000 10,000 14,000 Widen from 9 to 11 ft 3,000 3,000 4,000 5,000 5,000 8,000 Widen from 9 to 12 ft 3,000 3,000 4,000 5,000 6,000 8,000 Widen from 10 to 11 ft 4,000 4,000 6,000 7,000 8,000 11,000 Widen from 10 to 12 ft 4,000 4,000 6,000 7,000 8,000 11,000 Widen from 11 to 12 ft 16,000 19,000 28,000 32,000 37,000 55,000 Table 38. Example of AADT Levels at which Shoulder Widening Becomes Cost-Effective Rural Two-Lane Highway Segments Assuming 10-ft Lanes, Paved Shoulders, 1V:3H Roadside Foreslopes, and Moderate Horizontal Curvature Proposed Improvement Minimum AADT level (veh/day) for benefit-cost ratio = 1.0 Minimum AADT level (veh/day) for benefit-cost ratio = 2.0 Level Rolling Mountainous Level Rolling Mountainous Widen from 0 to 2 ft 3,000 4,000 6,000 6,000 8,000 12,000 Widen from 0 to 4 ft 3,000 4,000 5,000 6,000 7,000 10,000 Widen from 0 to 6 ft 3,000 4,000 5,000 6,000 7,000 9,000 Widen from 0 to 8 ft 3,000 4,000 5,000 6,000 7,000 9,000 Widen from 2 to 4 ft 5,000 6,000 9,000 10,000 12,000 17,000 Widen from 2 to 6 ft 4,000 5,000 6,000 8,000 9,000 12,000 Widen from 2 to 8 ft 4,000 4,000 6,000 8,000 8,000 11,000 Widen from 4 to 6 ft 6,000 7,000 10,000 12,000 13,000 19,000 Widen from 4 to 8 ft 5,000 5,000 7,000 9,000 10,000 14,000 Widen from 6 to 8 ft 8,000 9,000 12,000 16,000 17,000 24,000 5.5 Specific Benefit-Cost Analysis Applications for 3R Project Design Descriptions Three specific benefit cost-analysis applications have a role in 3R project design decisions. These are:  benefit-cost analysis for a single design alternative for a specific site  benefit-cost analysis to choose among several design alternatives for a specific site  benefit-cost analysis to develop agency-specific minimum AADT guidelines for application in design decisions

69 Each of these benefit-cost applications is discussed below. 5.5.1 Benefit-Cost Analysis for a Single Design Alternative for a Specific Site A single design alternative for a specific site can be evaluated by determining the benefit-cost ratio for the alternative using Equation (38). If the computed benefit-cost ratio equals or exceeds 1.0, the design alternative is cost-effective and implementation of the geometric design improvement deserves consideration as part of the 3R project. If the benefit-cost ratio is less than 1.0, the design alternative is not cost-effective and should not typically be considered as part of the 3R project unless the crash history shows a specific crash pattern that is potentially correctable by the geometric design improvement in question or the geometric design improvement is essential to achieving the traffic operational LOS for the project. An equivalent analysis can be performed by determining whether the net benefits determined with Equation (39) exceed zero. Highway agencies may prefer to seek minimum benefit-cost ratios greater than 1.0 to assure that limited funds available for safety improvements are invested productively. Benefit-cost analysis for a single design alternative can be performed with Spreadsheet Tool 1 presented below in Section 5.6.1. 5.5.2 Benefit-Cost Analysis to Choose Among Several Design Alternatives for a Specific Site Multiple design alternatives for a specific site can be evaluated by comparing their net benefits determined with Equation (39) and selecting for consideration the alternative that has the largest positive value of net benefits. If all of the design alternatives considered have net benefits less than zero, none of the alternatives are cost-effective and none deserve consideration as part of the 3R project unless the crash history shows a specific crash pattern that is potentially correctable by one or more of the design alternatives or that one or more of the design alternatives is essential to achieving the traffic operational LOS for the project. Highway agencies should consider budget constraints in choosing among multiple alternatives, and may also consider the magnitude of the benefit-cost ratio for the selected design alternative, computed with Equation (38), as focusing the expenditure of limited funds on design alternatives with benefit-cost ratios substantially greater than 1.0 helps assure that the funds available for safety improvements are invested productively. Benefit-cost analysis for multiple design alternatives can be performed with Spreadsheet Tool 2 presented below in Section 5.6.2.

70 5.5.3 Benefit-Cost Analysis to Develop Agency-Specific Minimum AADT Guidelines for Application in Design Decisions Highway agencies can develop minimum AADT guidelines for application in 3R project design decisions, analogous to those shown in Tables 37 and 38. Such guidelines can be developed through repeated application of Spreadsheet Tool 1, presented below in Section 5.6.1. Each entry in Tables 29 through 34 is obtained from a single application of Spreadsheet Tool 1. The results are then summarized in a form like Tables 35 and 36. The results like those in Tables 35 and 36 can then be expressed as minimum AADT guidelines like those presented in Tables 37 and 38. Benefit-cost analyses to establish minimum AADT guidelines should be based on generic site characteristics representative of a specific agency’s facilities. Separate minimum AADT guidelines are needed for each facility type and terrain category. All assumptions in the benefit- cost analysis, including implementation costs and crash costs, should be based on the policies and experience of an individual highway agency. Policies based on agency-specific minimum AADT guidelines are an acceptable method for making 3R project design decisions, but will not provide results as reliable as the site-specific benefit-cost analyses discussed in Sections 5.5.1 and 5.5.2. 5.6 Benefit-Cost Analysis Tools Two spreadsheet tools for benefit-cost analysis in support of 3R project design decisions are discussed in this section. These include a tool for analysis of a single design alternative (Spreadsheet Tool 1) and a tool for comparison of several design alternatives (Spreadsheet Tool 2). Each of these tools is discussed below. 5.6.1 Spreadsheet Tool 1—Benefit-Cost Analysis for a Single Design Alternative Spreadsheet Tool 1 is a spreadsheet-based benefit-cost analysis tool that can be used to assess the cost-effectiveness of specific improvement alternatives for implementation in conjunction with a 3R project. The tool helps users in making the decision as to whether the 3R project should consist of pavement resurfacing only or should also include geometric design improvements. Tool 1 is used to assess one improvement alternative (or combination of alternatives) at a time. Tool 2 (see Section 5.6.2 and Appendix B) can assess multiple alternatives (and combinations of alternatives) in a single analysis. Tool 1 can be applied as part of the planning process for 3R projects. If a specific project site has no observed crash patterns or no traffic operational needs that would justify a design improvement, then geometric design improvements are recommended for implementation as part of a 3R project only if it is anticipated that such improvements would be cost-effective. Tool 1 provides a capability to assess any particular improvement alternative (or combination of alternatives) to determine if it is anticipated to be cost-effective. Tool 1 addresses candidate 3R projects on rural two-lane highways, rural four-lane undivided and divided highways

71 (nonfreeways), and rural and urban freeways. The tool does not address 3R projects on urban and suburban arterials (nonfreeways). Examples of the application of Tool 1 are presented below in Sections 5.7.1 through 5.7.3 of this guide. A detailed users guide for Tool 1 is presented in Appendix A of this guide. The input data to Tool 1 include a description of the existing roadway conditions and selection by the user of the improvement(s) to be assessed. The tool considers a single set of AADT, terrain, and cross-section geometrics for the roadway between intersections within the candidate project being assessed. Variations in cross-section geometrics at intersections or on intersection approaches do not need to be considered in using the tool. Where there are minor variations in AADT on the project or in cross-section geometrics on the roadway between intersections within the project, the average AADT and the most common cross-section geometrics should be used as input to the tool. Thus, the tool can be applied even where the cross section throughout the project is not entirely homogeneous. Where there are major changes in cross-section geometrics on the roadway between intersections (e.g., half the project has 6-ft paved shoulders and half has 2-ft unpaved shoulders), the user can break the project into separate sections and analyze each section separately. Breaking the project into separate sections for analysis is only appropriate where the differences in cross-section geometrics are substantial. Tool 1 includes logic to estimate the implementation cost of the improvement alternatives evaluated. The project costs are estimated from default values of unit construction costs that are built into the tool. The user has the option to change these default unit costs to match their agency’s experience or to replace the project cost estimated by the tool with the agency’s own site-specific estimate. The user also has the option, for any given analysis, to include the cost of right-of-way acquisition in the project implementation cost estimate. Right-of-way costs can also be based on default values built into the tool, user-specific unit costs for right-of-way, or site- specific cost estimates made by the agency. The safety performance of the roadway being analyzed and the safety benefits of improvement alternatives estimated in Tool 1 are based on the crash prediction procedures presented in Part C of the AASHTO Highway Safety Manual (HSM) including HSM Chapters 10, 11, and 18 (1). The tool analyzes roadway segment (i.e., nonintersection) crashes only. The HSM crash prediction procedures are applied first to predict the crash frequencies by severity level for the existing roadway based on safety performance functions (SPFs), crash modification factors (CMFs), and local calibration factors (if available). The crash reduction effectiveness of improvements is based on the CMFs presented in Section 4.3 of this guide. The user has the option to replace the default SPFs from the HSM with their own agency-specific SPFs for all roadway types other than freeways. The local calibration factor is set equal to 1.0 by default, but may be replaced by the user with an agency-specific value. The user has the option to provide site-specific crash history data and apply the Empirical Bayes (EB) method for converting predicted crash frequencies to expected crash frequencies, using the procedures presented in the Appendix to HSM Part C. Crash costs by severity level are set by default to values built into the tool, but may be replaced by the user with agency-specific values.

72 The user of Tool 1 has the option to select which improvement alternative (or combination of alternatives) will be considered in the benefit-cost analysis. The improvement alternatives that may be considered include:  Lane widening  Shoulder widening (outside shoulder only on two-lane and four-lane nonfreeways; both outside and inside shoulders on freeways)  Shoulder paving (nonfreeways only)  Roadside slope flattening (two-lane and four-lane nonfreeways only)  Centerline rumble strips (undivided highways only)  Shoulder rumble strips (outside shoulder only on undivided roads; both outside and inside shoulders on divided nonfreeways and freeways)  Enhanced striping/delineation (nonfreeways only)  Add or modify median barrier (freeways only)  Add or modify roadside barrier (freeways only)  Add passing lane(s) (rural two-lane highways only)  Improve/restore curve superelevation (nonfreeways only) The results provided by Tool 1 for the analysis of any improvement alternative (or combination of alternatives) include:  Project implementation cost ($)  Annual safety benefit ($)  Present value of safety benefit ($)  Benefit-cost ratio (benefit divided by cost)  Net benefit (benefit minus cost) ($)  Fatal-and injury (FI) crashes per year in before period  Property-damage-only (PDO) crashes per year in before period  FI crashes per year in after period  PDO crashes per year after period  FI crashes per year reduced by project  PDO crashes per year reduced by project Tool 1 has been developed entirely in Microsoft Excel worksheets without any supplementary Visual Basic programming. This should make Tool 1 easily implementable on computers with nearly any operating system and nearly any version of Microsoft Excel. By contrast, Tool 2, presented in Appendix B, incorporates supplementary programming in Visual Basic; therefore, macros must be enabled on the user’s computer for Tool 2 to function. 5.6.2 Spreadsheet Tool 2—Benefit-Cost Analysis for Comparison of Several Design Alternatives Spreadsheet Tool 2 is a spreadsheet-based benefit-cost analysis tool that can be used to assess the cost-effectiveness of specific improvement alternatives for implementation in conjunction with a 3R project. The tool helps users in making the decision as to whether the 3R project should

73 consist of pavement resurfacing only or should also include geometric design improvements. Tool 2 has the capability to assess multiple improvement alternatives as a part of a single analysis and identify the most cost-effective alternative (or combination of alternatives). By contrast, Tool 1 considers only one alternative (or combination of alternatives) at a time. Tool 2 can be applied as part of the planning process for 3R projects. If a specific project site has no observed crash patterns or no traffic operational needs that would justify a design improvement, then geometric design improvements are recommended for implementation as part of a 3R project only if it is anticipated that such improvements would be cost-effective. Tool 2 provides a capability to assess all feasible improvement alternatives (or combinations of alternatives) for a given set of improvement types (see below). Like Tool 1, Tool 2 addresses candidate 3R projects on rural two-lane highways, rural four-lane undivided and divided highways (nonfreeways), and rural and urban freeways. The tool does not address 3R projects on urban and suburban arterials (nonfreeways). An example of the application of Tool 2 is presented below in Section 5.7.4 of this guide. A detailed users guide for Tool 2 is presented in Appendix B of this guide. The input data for Tool 2 include a description of the existing roadway conditions and selection by the user of the improvement(s) to be assessed. The roadway characteristics input data for Tool 2 are essentially identical to the roadway characteristics input data for Tool 1. The tool considers a single set of AADT, terrain, and cross-section geometrics for the roadway between intersections within the candidate project being assessed. Variations in cross-section geometrics at intersections or on intersection approaches do not need to be considered in using the tool. Where there are minor variations in AADT on the project or in cross-section geometrics on the roadway between intersections within the project, the average AADT and the most common cross-section geometric features should be used as inputs to the tool. Thus, the tool can be applied even where the cross section throughout the project is not entirely homogeneous. Where there are major changes in cross-section geometrics on the roadway between intersections (e.g., half the project has 6-ft paved shoulders and half has 2-ft unpaved shoulders), the user can break the project into separate sections and analyze each section separately. Breaking the project into separate sections for analysis is only appropriate where the differences in cross-section geometrics are substantial. Tool 2 includes logic to estimate the implementation cost of the improvement alternatives evaluated; the cost estimation logic in Tool 2 is essentially equivalent to the cost estimation logic in Tool 1. The project costs are estimated from default values of unit construction costs that are built into the tool. The user has the option to change these default unit costs to match their agency’s experience. The user also has the option, for any given analysis, to include the cost of right-of-way acquisition in the project implementation cost estimate. Right-of-way costs can also be based on default values built into the tool, user-specific unit costs for right-of-way. The safety performance of the roadway being analyzed and the safety benefits of improvement alternatives estimated in Tool 2 are based on the crash prediction procedures presented in Part C of the AASHTO Highway Safety Manual (HSM) including HSM Chapters 10, 11, and 18 (2,3). The tool analyzes roadway segment (i.e., nonintersection) crashes only. The HSM crash

74 prediction procedures are applied first to predict the crash frequencies by severity level for the existing roadway based on safety performance functions (SPFs), crash modification factors (CMFs), and local calibration factors (if available). The crash reduction effectiveness of improvements is based on the CMFs presented in Section 4.3 of this guide. The user has the option to replace the default SPFs from the HSM with their own agency-specific SPFs for all roadway types except freeways. The local calibration factor is set equal to 1.0 by default, but may be replaced by the user with an agency-specific value. The user has the option to provide site-specific crash history data and apply the Empirical Bayes (EB) method for converted predicted crash frequencies to expected crash frequencies, using the procedures presented in the Appendix to HSM Part C (2). Crash costs by severity level are set by default to values built into the tool, but may be replaced by the user with agency-specific values. The user of Tool 2 has the option to select which improvement alternatives (or combinations of alternatives) will be considered in the benefit-cost analysis. The improvement alternatives that may be considered include:  Lane widening  Shoulder widening (outside shoulder only on two-lane and four-lane nonfreeways; both outside and inside shoulders on freeways)  Shoulder paving  Roadside slope flattening (two-lane and four-lane nonfreeways only)  Centerline rumble strips (undivided highways only)  Shoulder rumble strips (outside shoulder only on undivided roads; both outside and inside shoulders on divided nonfreeways and freeways)  Enhanced striping/delineation (nonfreeways only)  Add or modify median barrier (freeways only)  Improve/restore curve superelevation (nonfreeways only) The results provided by Tool 2 for the analysis of any improvement alternative (or combination of alternatives) include:  Project implementation cost ($)  Present value of safety benefit ($)  Benefit-cost ratio (benefit divided by cost)  Net benefit (benefit minus cost) ($) The most cost-effective improvement alternative (or combination of alternatives) identified by Tool 2 is the alternative (or combination of alternatives) with the highest net benefit whose implementation cost is within the highway agency’s available budget. Because of its greater complexity, Tool 2 has most, but not all, of the capabilities of Tool 1 for allowing the user to change default values. For example, in Tool 2, the SPF coefficients from the HSM cannot be changed. Tool 2 has been developed in Microsoft Excel worksheets with supplementary Visual Basic programming. Therefore, macros must be enabled on the user’s computer for Tool 2 to function.

75 5.7 Application Examples Using the Benefit-Cost Spreadsheet Tools This section presents several examples of the analysis of 3R project alternatives using the benefit-cost analysis spreadsheet tools. These examples serve to illustrate how the tools are used to analyze 3R project alternatives on specific roadway types and how the tools can be applied for a sequence of analyses to address specific design decision scenarios. The examples presented are as follows:  Example 1—Assessment of specific improvement alternatives for a typical rural two-lane highway at two different AADT levels - Example 1A—Assessment of separate lane widening, shoulder paving, and superelevation improvement alternatives for a rural two-lane highway at two different AADT levels using Spreadsheet Tool 1 - Example 1B—Assessment of combined lane widening and superelevation improvement alternatives for the same rural two-lane highway at a higher AADT level (8,600 veh/day) using Spreadsheet Tool 1 - Example 1C—Assessment of separate lane widening, shoulder paving, and superelevation improvement alternatives for a rural two-lane highway considering site-specific crash history data using Spreadsheet Tool 1 - Example 1D—Achieving the same result as Examples 1A and 1B in one step using Spreadsheet Tool 2  Example 2—Quantifying minimum AADT levels for cost-effective application to two specific improvements on a rural two-lane highway  Example 3—Assessment of specific improvement alternatives for a typical rural four-lane highway  Example 4—Assessment of specific improvement alternatives for a typical freeway Examples 1 and 2 illustrate the full range of recommended applications of Spreadsheet Tools 1 and 2 for rural two-lane highways. Examples 3 and 4 are not intended to be as comprehensive as Example 1; rather, Examples 3 and 4 are presented to illustrate the variations in data entry and tool application for rural four-lane highways and freeways. The examples shown here illustrate the application of the spreadsheet-based tools in benefit-cost analysis. Detailed instructions for the application of Tools 1 and 2 are presented in Appendices A and B, respectively.

76 5.7.1 Example 1—Rural Two-Lane Highway Assessment A highway agency plans to resurface a section of rural two-lane highway and wants to assess if it would be cost-effective to include lane widening, shoulder widening, and/or superelevation improvements as part of the 3R project. Tables 39 and 40 describe the existing geometric design and other existing conditions for the roadway segment. Table 39 presents the section length, AADT, terrain, pavement type, and existing cross-section geometrics. Table 40 presents the geometrics of the four horizontal curves located within the project limits. Table 39. Existing Cross-Section Design and Other Existing Conditions for the Rural Two- Lane Highway in Example 1 Section Length 5 mi AADT 2,000 veh/day Terrain Rolling Pavement type Flexible Lane width 10.5 ft Unpaved shoulder width 4 ft Roadside slope 1V:4H Rumble strips present Centerline and Shoulder Maximum curve superelevation (emax) 8% Design speed 55 mph Table 40. Existing Horizontal Curve Geometrics for the Rural Two-Lane Highway in Example 1 Curve # Curve Length (mi) Transition Length (mi) Radius (ft) Spiral Present Existing Superelevation (%) 1 0.156 0.089 1,300 Yes 2.4 2 0.237 0.122 940 Yes 3.8 3 0.155 0.098 2,000 Yes 6.0 4 0.222 0.095 1,500 Yes 3.0 Example 1A—Assessment of Separate Lane Widening, Shoulder Paving, and Superelevation Alternatives for the Rural Two-Lane Highway in Example 1 at Two Different AADT Levels Using Spreadsheet Tool 1 First, Spreadsheet Tool 1 will be applied to determine if lane widening from the existing lane width of 10.5 ft to 12 ft would be cost-effective for this roadway segment. All default values provided in the R2U_Setup worksheet of Spreadsheet Tool 1 are used. In this analysis, potential right-of-way acquisition costs are not considered and existing crash history is either not available or is not considered. Construction costs are computed using the default unit costs in the R2U_Setup worksheet and the cost estimation procedures built into Tool 1.

Figures 7 Example R2U_Pro Figure 8 specific c horizonta F Figure 9 Fi Figure 10 this optio not be us through 12 1A are ente ject worksh Figure 7. R illustrates th urve data is l curves wil igure 8. A shows the ex gure 9. Exis shows the n means tha ed. Figure 10. C show screen red. Each fi eet in Tool oadway da e options fo chosen. Th l be entered lignment da isting cross ting cross s selected opt t the Empiri rash histo shots from gure is a scr 1. Figure 7 i ta input for r entry of al is option ind on a subseq ta option fo section dat ection data ion not to en cal Bayes m ry option fo 77 Spreadsheet eenshot of o llustrates the rural two- ignment dat icates that t uent screen r rural two a from Tabl for rural tw ter existing ethod in the r rural two Tool 1 illu ne particula roadway d lane highw a; in this cas he character . -lane highw e 39 that are o-lane hig crash histor AASHTO -lane highw strating how r table from ata entered f ay in Exam e, the optio istics of ind ay in Exam entered. hway in Ex y data for th Highway Sa ay in Exam input data f the or Example ple 1A n to enter ividual ple 1A ample 1A is site. Sele fety Manua ple 1A or 1A. cting l will

Figure 11 illustrate the Align Assessme Figure 12 considera 12 ft. Thi Figure Figure 13 two-lane Figure 13 of $223,5 would be illustrates t d in Figure 1 ment Data s Figure 11. nt of Lane W shows that tion of one s assessmen 12. User se shows how highway sp indicates th 31. The figu 0.360 and t he specific 1 only appe creen shown Specific cu idening Al , in the Alte potential im t considers lection of la the results ecified in Fi at the lane w re also indi he net benef curve data fr ars when th in Figure 8 rve data for ternative rnatives to C provement a lane widenin ne widenin lane highw of the lane w gures 7 thro idening is cates that th its (benefits 78 om Table 4 e option to e . rural two- onsider tab lternative, w g only, with g as an alte ay in Exam idening ass ugh 11, will expected to e benefit-co minus costs 0 that are en nter specifi lane highw le in Tool 1, idening the no other im rnative to b ple 1A essment spe appear in th cost $620,7 st ratio (ben ) would be tered into T c curve data ay in Exam the user ha existing 10 provement e assessed cified in Fig e Results se 94 and have efits divided -$397,263. T ool 1. The t is selected ple 1A s specified .5-ft lanes t s considered for rural tw ure 12, for ction of To safety bene by costs) he value of able on o . o- the ol 1. fits the

benefit-c widening Table 41 annual pr number o to the Re Figure Table Next, To with the to 8,600 Figure 7 The Resu the roadw higher be at this hig ost ratio less alternative shows the a edicted FI c f annual FI sults table. 13. Benefit h 41. Crash F H ol 1 is applie same charac veh/day. Th is changed t lts table fro ay if the AA nefits of $9 her AADT than 1.0 an is not cost-e nnual FI cra rash count f crashes redu -cost analy ighway wi requencies ighway wi Before FI Before PD After FI C After PDO Reduced Reduced d to consid teristics as p e only chang o 8,600 veh m Tool 1 sh DT is 8,60 61,182. The level, lane w d the negati ffective. sh count for or the period ced. The va sis results f th AADT of Before and th AADT o Crashes O Crashes rashes Crashes FI Crashes PDO Crashes er lane wide resented in e needed in /day. own in Figu 0 veh/day h benefit-cost idening to 79 ve value of n the period b after proje lues shown or widening 2,000 veh/ After Lan f 2,000 veh/ 0.88 1.87 0.80 1.69 0.08 0.17 ning from 1 Figures 7 th the input da re 14 indica as the same ratio is 1.54 12 ft would et benefits efore proje ct implemen in Table 41 lanes to 12 day in Exam e Widening day in Exa 4 crashes/yr 0 crashes/yr 3 crashes/yr 9 crashes/yr 1 crashes/yr 1 crashes/yr 0.5 ft to 12 rough 12 bu ta is that th tes that wid cost as in Fi 8 and the n be cost-effe indicate tha ct implemen tation, and are displaye ft for the r ple 1A for the Ru mple 1A ft on a two-l t with a hig e AADT of ening the lan gure 13, $62 et benefit is ctive. t the lane tation, the the predicte d in Tool 1 ural two-la ral Two-La ane highway her AADT e 2,000 veh/d es to 12 ft o 0,794, but $340,388. T d next ne ne qual ay in n hus

Figure Table 42 roadway Table Assessme The next existing 4 shoulder AADT o Figure 15 Alternati Figure 16 would no the costs Figure 17 veh/day, exceed th Based on shoulder considere 14. Benefit h shows the in assessed in 42. Crash F H nt of Should set of benef -ft unpaved paving cons f 2,000 veh/ shows the ves to Consi shows that t be cost-eff exceed the b shows that the shoulder e benefits. the results in conjuncti d. -cost analy ighway wi creased cra Figure 13. requencies ighway wi Before FI Before PD After FI C After PDO Reduced Reduced er Paving A it-cost asses shoulder, w iders the tw day. selection of der table in the benefits ective for th enefits. , even when paving imp of the benef on with the sis results f th AADT of sh reduction Before and th AADT o Crashes O Crashes rashes Crashes FI Crashes PDO Crashes lternative sments cons ith no other o-lane highw the shoulder Tool 1. of shoulder e two-lane h the AADT rovement a it-cost analy 3R project i 80 or widening 8,600 veh/ resulting fr After Lan f 8,600 veh/ 3.80 8.04 3.45 7.30 0.34 0.73 iders anothe improveme ay describe type impro paving are ighway at a of the rural lternative is ses in Figur s not cost-ef lanes to 12 day in Exam om lane wid e Widening day in Exa 2 crashes/yr 2 crashes/yr 5 crashes/yr 8 crashes/yr 7 crashes/yr 4 crashes/yr r improvem nts consider d in Figure vement to a very small a n AADT le two-lane hig still not cos es 16 and 17 fective at ei ft for the r ple 1A ening on th for the Ru mple 1A ent alternat ed. The firs s 7 through paved shou nd that shou vel of 2,000 hway is inc t-effective, s , paving the ther of the A ural two-la e higher AA ral Two-La ive, paving t t assessmen 12 with an lder in the lder paving veh/day, sin reased to 8,6 ince the cos unpaved ADT levels ne DT ne he t of ce 00 ts

Figure Figure 1 Figure 1 15. User sel 6. Benefit- 7. Benefit- ection of sh cost analysi with AA cost analysi with AA oulder pavi lane highw s results for DT of 2,00 s results for DT of 8,60 81 ng as an alt ay in Exam shoulder p 0 veh/day i shoulder p 0 veh/day i ernative to ple 1A aving for t n Example aving for t n Example be assessed he rural tw 1A he rural tw 1A for rural t o-lane high o-lane high wo- way way

Superele The next horizonta of 2,000 applicabl superelev in Tool 1 calculatio table with T Figure Figure 19 for the ru superelev Figure 20 for the ru the highe exceed th vation Impro analysis ass l curves to G and 8,600 v e to three of ation rates a . Figure 11 ns, with no supereleva able 43. Ho 18. Specifi shows the ral two-lane ation impro shows the ral two-lane r AADT lev e costs. vement Alte esses the co reen Book eh/day. Tabl the four ho re then inse shows the ex superelevat tion improv rizontal Cu c curve dat supe Results tabl highway w vement wou Results tabl highway w el, the super rnative st-effectiven criteria in co e 43 shows rizontal curv rted into the isting Spec ion specified ements for t rve Impro Curve # 1 2 3 4 a for rural relevation e from Tool ith an AAD ld not be co e from Tool ith a higher elevation im 82 ess of impr njunction w that superel es within th rightmost c ific Curve D . Figure 18 hree of the f ved Supere Improve Superelevat 7.6 8.0 No Chan 7.0 two-lane hi improveme 1 for assess T of 2,000 v st-effective 1 for assess AADT of 8 provement oving the su ith the 3R p evation imp e project lim olumn of th ata table us shows the u our horizon levation Ra d ion (%) ge ghway in E nts entered ment of the eh/day. The , since the co ment of the ,600 veh/day is cost-effec perelevation roject at bo rovements a its. These i e Specific C ed in the pre pdated Spec tal curves in tes for Exa xample 1A superelevati results show sts exceed superelevati . The result tive, since t on the th AADT le re potentiall mproved urve Data t vious exam ific Curve D dicated. mple 1A with potent on improve that the the benefits. on improve s show that he benefits vels y able ple ata ial ment ment , at

Figure Figure Results of The resul 2,000 veh 3R projec specific c service. For a rur and supe improvem superelev Example Alternat veh/day) A benefit widening of 8,600 combined benefits o 19. Benefit- lan 20. Benefit- lan Individual ts presented /day, none t on this roa rash pattern al two-lane h relevation im ent was no ation impro 1B—Asses ives for the using Spre -cost assess and supere veh/day. Fig lane widen f $1,113,42 cost analys e highway cost analys e highway Improvemen above show of the impro d should ge or a traffic ighway, wi provement t. Therefore vements as sment of C Same Rura adsheet To ment was pe levation imp ure 21 prese ing and sup 4. The bene is results fo with AADT is results fo with AADT t Alternativ that for the vement alte nerally be li operational th an AADT s were found , it is reason part of the 3 ombined La l Two-Lan ol 1 rformed wi rovement fo nts the resu erelevation fit-cost ratio 83 r superelev of 2,000 ve r superelev of 8,600 ve e Assessmen rural two-l rnatives con mited to res LOS below level of 8,6 to be cost- able to give R project. ne Wideni e Highway th Tool 1 co r the rural t lts of this as improvemen for the com ation impro h/day in Ex ation impro h/day in Ex ts ane highway sidered is co urfacing on the highway 00 veh/day effective, w consideratio ng and Sup at a Higher nsidering th wo-lane hig sessment. T ts would co bined impr vement for ample 1A vement for ample 1A with an AA st-effective ly, unless th agency’s ta , however, t hile the shou n to the lan erelevation AADT Lev e combined hway with a he figure sh st $652,331 ovements is the rural t the rural t DT level o . Therefore, ere is a site- rget level o he lane wide lder paving e widening Improvem el (8,600 effects of la n AADT lev ows that the and provide 1.707 and th wo- wo- f a f ning and ent ne el e

net benef should be Figur improve Example Superele Site-Spe So far in method f Tool 1 ca site-spec provide a Two case the comb increases data can scenarios 8,600 veh For the fi predictio injury cra Figure 22 is now an crash his Figures 2 improvem history d level of 8 it is $461,09 considered e 21. Benefi ments for t 1C—Asses vation Imp cific Crash Example 1, rom the AA n also consi ific crash his more accur s of analysi ined cost-ef the combin make impor analyzed fo /day. rst case, the n models. In sh and ten p shows that swered Yes tory data are 3 through 2 ent alterna ata, only the ,600 veh/da 3. Therefor for inclusio t-cost analy he rural tw sment of S rovement A History Da the crash re SHTO High der site-spe tory and the ate represen s with site-s fectiveness ed cost-effe tant contribu r Example site-specifi this case, fo roperty-dam the question . A Crash D entered by 5 show the R tives. The fi superelevat y remains c e, the combi n in the 3R sis results f o-lane high eparate Lan lternatives ta Using Sp duction ben way Safety M cific crash h crash predi tation of the pecific crash of the lane w ctiveness. T tions to the 1C apply to c crash histo r a crash hi age-only cr posed in th ata Table (a the user. esults table gures show ion improve ost-effective 84 ned lane wi project. or combine way with A e Widenin for a Rura readsheet T efits have be anual. To istory data u ctions are c site’s safet history dat idth and su he results in results of th the rural two ry data indi story period ashes on th e Crash His lso shown in s for the ben that, with co ment for the . dening and d lane wide ADT of 8,6 g, Shoulder l Two-Lane ool 1 en solely on add more co sing the Em ombined as y performan a are presen perelevation dicate that s e benefit-co -lane highw cate fewer c of three yea e rural two-l tory box sho Figure 22) efit-cost an nsideration rural two-l superelevati ning and s 00 veh/day Paving, an Highway C the crash p nfidence in pirical Bay a weighted a ce. ted here, on improveme ite-specific st analyses. ay with an rashes than rs, there wa ane highwa wn previou opens in To alyses of th of the site-s ane highway on improvem uperelevati in Exampl d onsidering rediction the analysis es method. T verage to e that decrea nts and one crash history All of the AADT leve the crash s one fatal-a y segment. sly in Figur ol 1 and the e individual pecific crash with an AA ent on e 1B , he ses that l of nd- e 10 DT

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Figure lane hig Example Spreadsh Spreadsh single ste Tool 2 w combinat level of 8 10.5 ft to considere Tool 2 ha combinat Tool 2 in user’s co Example crash his in the ana needed in not consi Figures 3 for the ru data entry 29. Benefit- hway with A 1D—Achie eet Tool 2 eet Tool 2 c p. When ap ill show in o ions) are co ,600 veh/da 12 ft and th d (or any of s an advant ions of alter corporates s mputer for T 1D uses all tory. The ex lysis. Tool this examp dered as an 0 through 3 ral two-lane tables show cost analys ADT of 8, ving the Sa an be used t plied to the ne step that st-effective. y, Tool 2 w e supereleva their comb age over To natives for t upplementa ool 2 to fun of the defau ample also d 2 can consid le, because improvemen 4 present sc highway w n in Figure is results fo 600 veh/day predicted me Results o obtain the rural two-lan none of the When appli ill show in o tion improv inations). ol 1 in that i hose improv ry programm ction. lt values pro oes not incl er pavemen adding enha t alternative reenshots of ith an AAD s 7 through 87 r superelev with site-s in Examp as Exampl same result e highway alternatives ed to the rur ne step that ement is the t can consid ement type ing in Visu vided in To ude conside t marking an nced pavem . the data ent T level of 2, 11. ation impro pecific cras le 1C es 1A and 1 s obtained in with an AAD considered al two-lane the combina most cost- er several im s in a single al Basic, ma ol 2 and doe ration of rig d delineato ent marking ry userform 000 veh/day vement for h history d B in One S Examples T level of (or any of th highway wi tion of lane effective of provement analysis. H cros must b s not consid ht-of-way a r data, but th s and roads windows sh , equivalent the rural t ata higher t tep Using 1A and 1B i 2,000 veh/d eir th an AADT widening f the alternati types and a owever, sinc e enabled o er existing cquisition c ese data are ide delineato owing the d to the Tool wo- han n a ay, rom ves ll e n the ost not rs is ata 1

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Figu Figure 35 alternativ combinat existing l specifyin Existing width wi superelev (4). Two unchange value to t Tool 2 fo improved four lane improvem re 34. Crash shows the es to be con ions of alter ane width o g that lane w Unpaved Sh ll be conside ation of eac alternatives d or (b) imp he Green B r each horiz supereleva widening al ent alterna history in dialogue box sidered. Too natives for t f 10.5 ft, che idths of 10 oulders spec red. Checki h curve to th are conside rove all cur ook superele ontal curve tion rates m ternatives, t tives, repres put for rura used by th l 2 automat he specified cking Wide .5, 11.0, 11. ifies that bo ng Improve e superelev red: (a) leav ves with sup vation value are summar atch those sh wo shoulder enting 16 co 90 l two-lane e analyst in ically consi improveme n Lane Wid 5, and 12.0 f th unpaved Curve Supe ation indica e all curves erelevation . The impro ized in Tabl own previo paving alte mbinations highway fo Tool 2 to sp ders all feas nt types. Fo th in Figure t will be con and paved s relevation s ted in AASH with their ex below the G ved superel e 44; it shou usly in Tabl rnatives, an of alternativ r Example ecify the im ible alternat r example, g 35 is equiv sidered. Ch houlders of tarts a comp TO Green isting supe reen Book evation rate ld be noted e 43. This in d two supere es are consi 1D in Tool provement ives and iven the alent to ecking Pave the current arison of th Book criteri relevation superelevati s identified that these cludes a tot levation dered. 2 e a on by al of

Figure The resul level of 2 alternativ classified also show available scenarios This is th 35. User se Table 44. M ts of the ana ,000 veh/da es) are sorte based on th s the total c budget can have net be e same conc lection of im for rur inimum G Curv 1 2 3 4 lysis condu y are summ d from mos e net benefi ost for each be eliminate nefits less th lusion reach provemen al two-lane reen Book S e Im cted with To arized Table t cost-effect t resulting f improveme d from cons an zero, so ed after mu 91 t alternativ highway in uperelevat proved Super 7.6 8.0 No Change 7.0 ol 2 for the 45. The im ive to least c rom implem nt scenario ideration. In none of the ltiple applic es to be con Example ion Rates P elevation (%) Needed rural two-la provement s ost-effectiv entation of t so that scena Table 45, scenarios ar ations of To sidered in T 1D rovided by ne highway cenarios (co e, with cost he alternativ rios that ex all of the im e considere ol 1. ool 2 selec Tool 2 with an AA mbinations -effectivene e. The tabl ceed the provement d cost-effect ted DT of ss e ive.

92 Table 45. Results of Benefit-Cost Analysis Using Tool 2 for a Rural Two-Lane Highway with AADT Level of 2,000 veh/day in Example 1D Net Benefit ($) B/C Ratio Improved Lane Width (ft) Improved Shoulder Type Improve Super- elevation Total Benefit ($) Total Cost ($) -$22,662 0.632 10.5 Unpaved Yes $38,962 $61,624 -$284,419 0.408 11 Unpaved Yes $196,086 $480,505 -$294,340 0.352 11 Unpaved No $159,665 $454,005 -$338,853 0.402 11.5 Unpaved Yes $227,511 $566,364 -$345,801 0.357 11.5 Unpaved No $191,598 $537,399 -$393,395 0.397 12 Unpaved Yes $258,936 $652,331 -$397,263 0.360 12 Unpaved No $223,531 $620,794 -$484,835 0.030 10.5 Paved No $14,793 $499,628 -$492,156 0.098 10.5 Paved Yes $53,520 $545,676 -$717,036 0.195 11 Paved No $173,494 $890,530 -$730,113 0.223 11 Paved Yes $209,695 $939,808 -$768,690 0.211 11.5 Paved No $205,234 $973,924 -$785,612 0.235 11.5 Paved Yes $240,930 $1,026,542 -$820,345 0.224 12 Paved No $236,974 $1,057,318 -$841,221 0.244 12 Paved Yes $272,165 $1,113,386 The same assessment was then rerun with a higher AADT, changing the AADT value in the input data in Figure 30 from 2,000 to 8,600 veh/day. The results of this second analysis for Example 1D are presented in Table 46, sorted by net benefits value in order from most cost- effective to least cost-effective. In Table 46, given the higher AADT value than Table 45, several improvement scenarios have net benefits greater than zero. The highest net benefits value is for the combination of lane widening to 12 ft and superelevation improvement. This is the same conclusion reached after multiple applications of Tool 1. Table 46. Results of Benefit-Cost Analysis Using Tool 2 for a Rural Two-Lane Highway with AADT Level of 8,600 veh/day in Example 1D Net Benefit ($) B/C Ratio Improved Lane Width (ft) Improved Shoulder Type Improve Super- elevation Total Benefit ($) Total Cost ($) $461,093 1.707 12 Unpaved Yes $1,113,424 $652,331 $411,934 1.727 11.5 Unpaved Yes $978,297 $566,364 $362,665 1.755 11 Unpaved Yes $843,170 $480,505 $340,388 1.548 12 Unpaved No $961,182 $620,794 $286,471 1.533 11.5 Unpaved No $823,870 $537,399 $232,554 1.512 11 Unpaved No $686,559 $454,005 $105,912 2.719 10.5 Unpaved Yes $167,535 $61,624 $56,924 1.051 12 Paved Yes $1,170,310 $1,113,386 $9,457 1.009 11.5 Paved Yes $1,035,999 $1,026,542 -$38,119 0.959 11 Paved Yes $901,688 $939,808 -$38,332 0.964 12 Paved No $1,018,987 $1,057,318 -$91,419 0.906 11.5 Paved No $882,505 $973,924 -$144,507 0.838 11 Paved No $746,022 $890,530 -$315,541 0.422 10.5 Paved Yes $230,134 $545,676 -$436,017 0.127 10.5 Paved No $63,611 $499,628

93 5.7.2 Example 2—Quantifying Minimum AADT Levels for Cost-Effective Application of a Selected Improvement Type on a Rural Two-Lane Highway In Example 2, an agency wants to construct a table of minimum AADT values that can be used as a guideline for the situations under which lane widening should be considered in 3R projects on rural two-lane highways. While application of Tool 1 or Tool 2 to each individual 3R project site would produce more accurate results, Section 5.4 of this guide indicates that application of such minimum AADT tables is an acceptable method for making 3R project decisions for specific improvement types. Minimum AADT tables for specific improvement types can be created with Tool 1 using agency specific assumptions for all setup variables in Tool 1 including, if desired, agency-specific values for unit construction costs, crash costs, SPF coefficients and or calibration factors. In addition, agencies can chose whether to include or omit right-of way costs from the calculations and, if right-of-way costs are included, agency-specific values of right-of- way cost per acre for specific area types and road types can be used. In Example 2, an agency chooses to develop minimum AADT tables for lane widening on rural two-lane highways using the assumed set of existing conditions presented in Table 47. Use Tool 1 to calculate benefit-cost ratios for every 1,000 veh/day increments of AADT. Use the road attributes given in Table 47 to input into Tool 1. Table 47. Roadway Attributes for Rural Two-Lane Highway Considered in Example 2 Section Length 1 mi AADT 1,000 to 20,000 veh/day Terrain Level Pavement Type Flexible Paved Shoulder Width 2 ft Roadside Slope 1V:3H Rumble Strips Present None Horizontal Curves None Tool 1 is then applied to lane widening from 9 to 10 ft for AADTs beginning at 1,000 veh/day and increasing in increments of 1,000 veh/day. The results are shown in Table 48. Table 48. Benefit-Cost Ratios for Lane Widening from 9 to 10 ft on Rural Two-Lane Highway Segment at Various AADT Levels for Example 2 Lane Width (ft) AADT (veh/day) Net Implementation Cost ($) Present Value of Safety Benefits ($) Benefit-Cost RatioBefore After 9 10 1,000 109,896 13,904 0.13 9 10 2,000 109,896 63,767 0.58 9 10 3,000 109,896 95,899 0.87 9 10 4,000 109,896 127,865 1.16 9 10 5,000 109,896 159,832 1.45 9 10 6,000 109,896 191,798 1.74 9 10 7,000 109,896 223,764 2.04 9 10 8,000 109,896 255,731 2.33 9 10 9,000 109,896 287,697 2.62 9 10 10,000 109,896 319,663 2.91 NOTE: Assumed conditions – 2-ft paved shoulder; 1V:3H roadside foreslopes; flexible pavement

94 According to the results shown in Table 48, widening a rural two-lane highway with 9-ft lanes to 10-ft lanes will produce a benefit-cost ratio greater than 1.0 at AADTs of 4,000 veh/day and higher. Widening will also produce benefit-cost ratios greater than 2.0 at AADTs 7,000 veh/day and higher. This same analysis can then be repeated for each additional lane widening scenario: 9 to 11 ft, 9 to 12 ft, 10 to 11 ft, 10 to 12 ft, and 11 to 12 ft. Based on the results of these analyses, a table can be constructed showing minimum AADT levels that would provide benefit-cost ratios of at least 1.0 and 2.0 for each lane widening scenario (see Table 49). Table 49. Minimum AADT Levels at which Benefit-Cost Ratios Exceed 1.0 and 2.0 for Lane Widening for Example 2 Lane Widening Scenario Minimum AADT (veh/day) for B/C=1.0 B/C=2.0 Widen from 9 to 10 ft 4,000 7,000 Widen from 9 to 11 ft 3,000 5,000 Widen from 9 to 12 ft 3,000 5,000 Widen from 10 to 11 ft 3,000 6,000 Widen from 10 to 12 ft 4,000 7,000 Widen from 11 to 12 ft 14,000 >20,000 The minimum AADT thresholds shown in Table 49 apply only to rural two-lane highways with the attributes shown previously in Table 47. Similar analyses can be conducted for rural two-lane highways in other terrains (see Table 50) as well as varying shoulder widths and roadside slopes (see Table 51) for example. Table 50. AADT Levels at which Lane Widening Becomes Cost-Effective on Rural Two- Lane Highways Assuming 2-ft Paved Shoulders and 1V:3H Roadside Foreslopes for Example 2 Proposed Improvement Minimum AADT level (veh/day) for benefit-cost ratio = 1.0 Minimum AADT level (veh/day) for benefit-cost ratio = 2.0 Level Rolling Mountainous Level Rolling Mountainous 9-ft existing lane width Widen from 9 to 10 ft 4,000 4,000 6,000 7,000 8,000 12,000 Widen from 9 to 11 ft 3,000 3,000 4,000 5,000 5,000 7,000 Widen from 9 to 12 ft 3,000 3,000 4,000 5,000 5,000 7,000 10-ft existing lane width Widen from 10 to 11 ft 3,000 4,000 5,000 6,000 7,000 10,000 Widen from 10 to 12 ft 4,000 4,000 5,000 7,000 7,000 10,000 11-ft existing lane width Widen from 11 to 12 ft 14,000 16,000 >20,000 >20,000 >20,000 >20,000

95 Table 51. AADT Levels at which Lane Widening Becomes Cost-Effective on Rural Two- Lane Highways Assuming 4-ft Paved Shoulders and 1V:6H Roadside Foreslopes for Example 2 Proposed Improvement Minimum AADT level (veh/day) for benefit-cost ratio = 1.0 Minimum AADT level (veh/day) for benefit-cost ratio = 2.0 Level Rolling Mountainous Level Rolling Mountainous 9-ft existing lane width Widen from 9 to 10 ft 8,000 9,000 13,000 15,000 17,000 >20,000 Widen from 9 to 11 ft 4,000 5,000 7,000 8,000 9,000 13,000 Widen from 9 to 12 ft 4,000 5,000 7,000 8,000 9,000 13,000 10-ft existing lane width Widen from 10 to 11 ft 6,000 7,000 11,000 12,000 14,000 >20,000 Widen from 10 to 12 ft 6,000 7,000 10,000 12,000 13,000 20,000 11-ft existing lane width Widen from 11 to 12 ft >20,000 >20,000 >20,000 >20,000 >20,000 >20,000 Based on tables like Tables 50 and 51, the agency can establish specific guidelines for the minimum AADT levels at which specific lane widening scenarios will be established. 5.7.3 Example 3—Rural Four-Lane Highway Assessment Example 3 is presented to illustrate the application of Tools 1 and 2 to a rural four-lane highway. Example 3 is presented primarily to illustrate the data entry procedures for rural four-lane highways, and this example is not intended to be as comprehensive as Example 1. In Example 3, a 3R project is being planned for a section of rural four-lane undivided highway. Tools 1 and 2 are used to assess whether specific proposed improvements, to supplement pavement resurfacing, are economically justifiable. The example uses default values provided for all data elements in the R4UD_Setup worksheet. The existing roadway and cross section data are shown in Table 52. Table 52. Roadway Characteristics for Rural Four-Lane Undivided Highway in Example 3 Road Type Four-lane Undivided Section Length 3.2 mi AADT 28,000 veh/day Terrain Level Pavement Rigid Lane Width 12 ft Paved Shoulder Width 2 ft Roadside Slope 1V:2H Rumble Strips Present Centerline Only Roadside Delineators Present on entire length of section Crash History Period 5 yr Number of Fatal-and-injury Crashes 20 Number of Property-damage-only Crashes 41 Maximum Curve Superelevation 8% Design Speed 65 mph

There is geometri Curve Leng Curve Rad Presence o Existing Su The agen roadside strip, and Figures 3 Figure 3 Figure 3 only one hor c data for th Ta th ius f Spiral Trans perelevation R cy planning slope to 1V adding enh 6 through 4 Figure 36. 7. Existing 8. Crash da izontal curv is curve. ble 53. Spe itions ate the 3R proj :6H, installin anced pavem 1 show how Roadway d cross sectio ta input for e within the cific Horizo ect wants to g shoulder ent markin the project ata input fo n data inpu rural four 96 project lim ntal Curve 0.102 mi 4000 ft No 3.0% determine t rumble strip gs and delin inputs shoul r rural fou t for rural -lane highw its. Table 53 Data for E he economi s, re-installi eation as pa d appear in r-lane highw four-lane h ays in Exam presents th xample 3 c feasibility ng the cente rt of the 3R the spreadsh ays in Exa ighways in ple 3 e available of flattening rline rumble project. eet-based to mple 3 Example 3 the ol.

Figure Figure The bene 40. Alterna 41. Project fit-cost anal Figure tives to con right-of-w ysis results 39. Specific sider selecti ay cost incl E are shown in 97 curve data on for the r usion option xample 3 Figure 42. for Examp ural four-l for the ru le 3 ane highwa ral four-lan y in Examp e highways le 3 in

The resul benefit-c To verify marking each of th them. In fact, th shoulders how shou combinat pavemen The resul improvem shoulder alternativ that shou unless an shoulders In fact, th combinat assessed installatio most cos will resul 1V:6H, in improvem should be striping/d Figure 42. R ts of the eco ost ratio of 2 that slope f and delineat ese improv e highway a , however t lder wideni ions of slop t marking an ts of the ana ent alterna widening al es in which lder widenin existing cra . e alternativ ion of slope in Figure 40 n, and strip t-effective c t in a net be stalling sho ent cost est given to in elineation i esults of a nomic analy .5. lattening, sh ion should a ements indiv gency plann he agency is ng should b e flattening d delineatio lysis with T tives that To ternatives sh the existing g is not cos sh pattern o e improvem flattening, . This confi ing/delineat ombination nefit lower t ulder rumbl imate of $1 cluding the mprovemen nalysis for t sis indicate oulder rumb ll be includ idually or T ing the proj unsure whe e considered (1V:2H to 1 n, and shou ool 2 are sh ol 2 indicate own in Tab shoulder w t-effective a r a traffic op ent with the shoulder rum rms that slop ion are cost- of alternativ han the net e strips, and ,091,554 is w slope flatten t as part of t 98 he rural fo an econom le strip inst ed in the pro ool 2 shoul ect also wa ther wideni . To address V:6H), shou lder widenin own in Tabl s will produ le 54 produc idth of 2 ft i nd need not erational an highest net ble strip in e flattening effective in es. The resu benefit prod improving ithin the ag ing, shoulde he 3R projec ur-lane hig ically justifi allation, and ject, either d be used to nts consider ng would be this issue, lder rumble g (2 to 8 ft) e 54. The ta ce the high e net benef s retained. T be consider alysis indic benefits sho stallation, an to 1V:6H, s dividually a lts indicate uced by flat the striping ency’s bud r rumble str t. hway in Ex able 3R proj enhanced p Tool 1 shou look at all c widening th cost-effecti Tool 2 is run strip install . ble shows th est net bene its smaller th hus, it can b ed as part o ates the nee wn in Table d striping/d houlder rum nd, together that any sho tening the r and delinea get, strong c ip installatio ample 3 ect, with a avement ld be run for ombination e paved ve and, if so for all ation, enhan e 15 fits. All of th an the e concluded f the 3R proj d for wider 54 is the sa elineation ble strip represent th ulder widen oadside slop tion. If the onsideration n, and s of , ced e ect, me e ing e to

99 Table 54. Results of Analysis for Shoulder Widening, Slope Flattening and Installing Shoulder Rumble Strips Net Benefit ($) B/C Ratio Improved Shoulder Width (ft) Improved Slope Install Shoulder Rumble Strip Improve Striping/ Delineation Total Benefit ($) Total Cost ($) $1,683,575 2.542 2 1V:6H Yes Yes $2,775,129 $1,091,554 $1,602,645 2.488 2 1V:6H No Yes $2,679,533 $1,076,888 $1,462,796 2.429 2 1V:4H Yes Yes $2,486,452 $1,023,657 $1,375,492 2.363 2 1V:4H No Yes $2,384,483 $1,008,991 $1,373,026 2.387 2 1V:3H Yes Yes $2,362,734 $989,708 $1,351,152 2.522 2 1V:2H Yes Yes $2,239,015 $887,863 $1,282,991 2.316 2 1V:3H No Yes $2,258,033 $975,043 $1,258,386 2.441 2 1V:2H No Yes $2,131,584 $873,197 $1,207,517 1.739 3 1V:6H Yes Yes $2,840,435 $1,632,918 $1,128,029 1.697 3 1V:6H No Yes $2,746,281 $1,618,252 $1,073,659 1.586 4 1V:6H Yes Yes $2,905,742 $1,832,082 $995,612 1.548 4 1V:6H No Yes $2,813,029 $1,817,417 $991,091 1.633 3 1V:4H Yes Yes $2,556,112 $1,565,021 $939,801 1.463 5 1V:6H Yes Yes $2,971,048 $2,031,247 $905,326 1.584 3 1V:4H No Yes $2,455,681 $1,550,356 5.7.4 Example 4—Freeway Assessment Example 4 is presented to illustrate the application of Tool 1 to a rural freeway. Example 4 is presented primarily to illustrate the data entry procedures for freeways, and this example is not intended to be as comprehensive as Example 1. In Example 4, a 3R project is planned for a section of rural freeway. Tool 1 is used to assess whether specific proposed improvements, to supplement resurfacing, are economically justifiable. The example uses default values provided for all data elements in the FWY_Setup worksheet. The existing freeway attributes are shown in Table 55.

100 Table 55. Freeway Attributes for Example 4 Section Length 3 mi AADT 45,000 veh/day Terrain Rolling Pavement Flexible Percent of Section Length on Horizontal Curves 15% Typical Curve Radius 3,250 ft Number of Horizontal Curves 4 Number of Through Lanes 4 Lane Width 12 ft Outside Shoulder Width 4 ft Inside Shoulder Width 2 ft Outside Roadside Slope 1V:3H Median Width 30 ft Median Cross Slope 1V:6H Presence of Median Barriers No Presence of Outside Barriers Yes Clear Zone Width 20 ft Rumble Strips Present Inside and Outside Shoulders Proportion of AADT During Hours Where Volume Exceeds 1,000 veh/h/ln 0 Characteristics of the four existing outside barriers within the project limits are presented in Table 56. Table 56. Outside Barrier Characteristics for Example Problem Outside Barrier Length of Outside Barrier (mi) Horizontal Clearance (ft) Barrier Type 1 0.125 mi 5.0 ft Guardrail 2 0.400 mi 8.0 ft Cable Barrier 3 0.100 mi 6.0 ft Concrete Barrier 4 0.100 mi 6.0 ft Concrete Barrier The highway agency has decided to investigate possible implementation of widening the outside shoulder width to 12 ft and widening the inside shoulder width to 12 ft. It is assumed that right- of-way acquisition is not needed. Figures 43 through 51 show how this example problem should be setup in the spreadsheet-based tool.

Fig Figu Figure Figure ure 43. Roa re 44. Align 45. Averag 46. Crash dway data ment optio e curve dat history opti 101 input for a n input for a input for on input fo freeway in a freeway i a freeways r a freeway Example 4 n Example in Exampl in Exampl 4 e 4 e 4

Figure 47 Figure Figure . Existing c 48. Outside 49. Outsid ross section barrier co e barrier da 102 data input unt input fo ta input fo for a freew r a freeway r a freeway ay in Exam in Examp in Exampl ple 4 le 4 e 4

Fig The resul Figur Table 57 Tab Before FI Before PD After FI C After PDO Reduced Reduced ure 50. Dat Figure 51. ts of the ana e 52. Benef shows the o le 57. Befor Crashes O Crashes rashes Crashes FI Crashes PDO Crashes a entry tab Right-of-w lysis are sh it-cost anal bserved and e, After an le for select Ex ay cost incl own in Figu ysis results freeway estimated c d Reduced E 103 ing alterna ample 4. usion option re 52. for inside a in Examp rash frequen Crash Freq xample 4 8.513 cra 17.283 c 5.224 cra 14.544 c 3.289 cra 2.739 cra tives to con for a freew nd outside le 4 cies before uencies on shes/yr rashes/yr shes/yr rashes/yr shes/yr shes/yr sider for a ay in Exam shoulder w and after th Freeway 3R freeway in ple 4. idening for e 3R project Project in a .

104 The results of the economic analysis indicate the proposed inside and outside shoulder widening is economically justified with a positive net benefit of $6,442,622. Tool 2 was then used to verify that both the inside and outside shoulder widening are cost- effective individually and that the widening of both the inside and outside shoulders to 12 ft is the combination of alternatives with the highest net benefit. Some highway agencies have policies that limit inside shoulder width to 4 ft to encourage drivers that need to stop to use the outside shoulder. Nothing in the results of a benefit-cost analysis like that shown here would require a highway agency to make the inside shoulders wider than indicated in their policy.

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Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects Get This Book
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TRB's National Cooperative Highway Research Program (NCHRP) has released a pre-publication, non-edited version of Research Report 876: Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. The report presents an approach for estimating the cost-effectiveness of including safety and operational improvements in a resurfacing, restoration, or rehabilitation (3R) project. The approach uses the performance of the existing road in estimating the benefits of a proposed design improvement and in determining if it is worthwhile. These guidelines are intended to replace TRB Special Report 214: Designing Safer Roads: Practices for Resurfacing, Restoration, and Rehabilitation. The guidelines are accompanied by two spreadsheet tools available for download through a .zip file: one for analyzing a single design alternative and one for comparing several alternatives or combinations of alternatives.

Disclaimer: This software is offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences or the Transportation Research Board (collectively "TRB") be liable for any loss or damage caused by the installation or operation of this product. TRB makes no representation or warranty of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular purpose, and shall not in any case be liable for any consequential or special damages.

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