Developing Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects (2021)

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94 Chapter 8. Spreadsheet Tools to Perform Benefit–cost Analysis for 3R Improvement Alternatives Two spreadsheet tools for benefit–cost analysis in support of 3R project design decisions have been developed in the current research and are discussed in this chapter. 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. 8.1 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 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 suggested 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 (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 and a detailed user’s guide for Tool 1 are presented in accompanying 3R design guidelines (9). 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

95 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 (6,7). 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 Chapter 5 of this report. 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. 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)

96 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, has also been developed in Microsoft Excel but incorporates supplementary programming in Visual Basic; therefore, macros must be enabled on the user’s computer for Tool 2 to function. 8.2 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 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 suggested for implementation as part of a 3R project only if it is anticipated that such improvements would be cost-effective based on the anticipated crash reduction. 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 and a detailed user’s guide for Tool 2 are presented in the accompanying 3R design guidelines (9).

97 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 or 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 (6,7). 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 Chapter 5 of this report. 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.

98 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.