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Suggested Citation:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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:"Front Matter." 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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© 2018 National Academy of Sciences. All rights reserved. ACKNOWLEDGMENTS The research for this document was conducted through one or more programs administered by the Cooperative Research Programs (CRP) of the Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine:  Airport Cooperative Research Program (ACRP) research is sponsored by the Federal Aviation Administration (FAA).  Hazardous Materials Cooperative Research Program (HMCRP) research is sponsored by the Pipeline and Hazardous Materials Safety Administration (PHMSA).  National Cooperative Freight Research Program (NCFRP) research is sponsored by the Office of the Assistant Secretary for Research and Technology.  National Cooperative Highway Research Program (NCHRP) research is sponsored by the American Association of State Highway and Transportation Officials (AASHTO), in cooperation with the Federal Highway Administration (FHWA).  National Cooperative Rail Research Program (NCRRP) research is sponsored by the Federal Railroad Administration.  Transit Cooperative Research Program (TCRP) research is sponsored by the Federal Transit Administration (FTA) in cooperation with the Transit Development Corporation. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply endorsement by TRB and any of its program sponsors of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. DISCLAIMER To facilitate more timely dissemination of research findings, this pre-publication document is taken directly from the submission of the research agency. The material has not been edited by TRB. The opinions and conclusions expressed or implied in this document are those of the researchers who performed the research. They are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board, the National Academies, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of the report. This pre-publication document IS NOT an official publication of the Cooperative Research Programs; the Transportation Research Board; or the National Academies of Sciences, Engineering, and Medicine. Recommended citation: Harwood, D. W., D. J. Cook, R. Coakley, and C. Polk. 2018. Guidelines for Integrating Safety and Cost-Effectiveness into Resurfacing, Restoration, and Rehabilitation (3R) Projects. Pre-publication draft of NCHRP Research Report 876. Transportation Research Board, Washington, D.C.

iii Contents Summary .......................................................................................................................................ix Chapter 1.  Introduction ....................................................................................................................1  1.1 Purpose of Guidelines .............................................................................................1  1.2 Scope of Guidelines ................................................................................................1  1.3 History of Guidelines ..............................................................................................2  1.4 Organization of Guidelines .....................................................................................3  Chapter 2. What are 3R Projects? ....................................................................................................4  2.1 New Construction vs. Reconstruction vs. 3R Projects ...........................................4  2.2 Objectives of 3R Projects ........................................................................................5  2.3 Typical Improvements Made in 3R Projects in Addition to Resurfacing ...............6  Chapter 3. Process for 3R Project Development .............................................................................7  3.1 How Does the Design Process for 3R Projects Differ from the Design Process for New Construction and Reconstruction Projects? .................................7  3.2 How Should Candidate 3R Projects Be Identified? ................................................9  3.3 Assessment of Needs for Improvements in Addition to Resurfacing ...................10  Chapter 4. Managing a 3R Program to Reduce Crash Frequency and Severity ............................17  4.1 Role of 3R Projects in Overall Safety Management Programs of Highway Agencies ...............................................................................................................17  4.2 Quantifying Crash Reduction Effectiveness of 3R Improvements: Crash Modification Factors (CMFs) ...............................................................................18  4.3 Crash Modification Factors for Specific 3R Improvement Types ........................22  4.4 Investing Available 3R Funds for Maximum Reduction of Crash Frequency and Severity ..........................................................................................................43  Chapter 5. Application of Benefit-Cost Analysis for 3R Projects .................................................47  5.1 Elements of Benefit-Cost Analysis .......................................................................47  5.2 Computational Examples of Benefit-Cost Analysis .............................................56  5.3 Interpreting Benefit-Cost Analysis Results ..........................................................61  5.4 Using Benefit-Cost Analysis to Establish Minimum AADT Guidelines for 3R Improvements ............................................................................................65  5.5 Specific Benefit-Cost Analysis Applications for 3R Project Design Descriptions ..........................................................................................................68  5.6 Benefit-Cost Analysis Tools .................................................................................70  5.7 Application Examples Using the Benefit-Cost Spreadsheet Tools .......................75 

iv Chapter 6. 3R Project Design Guidelines for Specific Roadway Types .....................................105  6.1 Rural Two-Lane Highways .................................................................................105  6.2 Rural Multilane Undivided Highways ................................................................116  6.3 Rural Multilane Divided Highways (Nonfreeways) ...........................................123  6.4 Urban and Suburban Arterials ............................................................................129  6.5 Rural and Urban Freeways..................................................................................132  Chapter 7. Summary of 3R Design Guidelines ...........................................................................135  Chapter 8. References ..................................................................................................................138  Appendices Appendix A—Users Guide for Spreadsheet Tool 1 Appendix B—Users Guide for Spreadsheet Tool 2 Appendix C—Updated Crash Cost Estimates

v Figures Figure 1. Example collision diagram from Safety Analyst ..........................................................13  Figure 2. CMFra for Lane Width on Undivided Roadway Segments on Rural Two-Lane Roadway Segments ......................................................................................................23  Figure 3. Crash Modification Factor for Shoulder Width on Roadway Segments for Two-lane Highway .......................................................................................................25  Figure 4. CMFra for Lane Width on Undivided Roadway Segments on Rural Multilane Highways .....................................................................................................................30  Figure 5. CMFra for Lane Width on Divided Roadway Segments on Rural Multilane Highways .....................................................................................................................33  Figure 6. Roadway data input for rural two-lane highway in Example 1A ................................77  Figure 7. Alignment data option for rural two-lane highway in Example 1A ............................77  Figure 8. Existing cross section data for rural two-lane highway in Example 1A ......................77  Figure 9. Crash history option for rural two-lane highway in Example 1A ................................77  Figure 10. Specific curve data for rural two-lane highway in Example 1A ..................................78  Figure 11. User selection of lane widening as an alternative to be assessed for rural two-lane highway in Example 1A ................................................................................78  Figure 12. Benefit-cost analysis results for widening lanes to 12 ft for the rural two-lane highway with AADT of 2,000 veh/day in Example 1A ..............................................79  Figure 13. Benefit-cost analysis results for widening lanes to 12 ft for the rural two-lane highway with AADT of 8,600 veh/day in Example 1A ..............................................80  Figure 14. User selection of shoulder paving as an alternative to be assessed for rural two-lane highway in Example 1A ................................................................................81  Figure 15. Benefit-cost analysis results for shoulder paving for the rural two-lane highway with AADT of 2,000 veh/day in Example 1A ..............................................81  Figure 16. Benefit-cost analysis results for shoulder paving for the rural two-lane highway with AADT of 8,600 veh/day in Example 1A ..............................................81  Figure 17. Specific curve data for rural two-lane highway in Example 1A with potential superelevation improvements entered ..........................................................................82  Figure 18. Benefit-cost analysis results for superelevation improvement for the rural two-lane highway with AADT of 2,000 veh/day in Example 1A ...............................83  Figure 19. Benefit-cost analysis results for superelevation improvement for the rural two-lane highway with AADT of 8,600 veh/day in Example 1A ...............................83  Figure 20. Benefit-cost analysis results for combined lane widening and superelevation improvements for the rural two-lane highway with AADT of 8,600 veh/day in Example 1A .............................................................................................................84  Figure 21. Entering site-specific crash data for Example 1C with site-specific crash history lower than predicted .........................................................................................85  Figure 22. Benefit-cost analysis results for lane widening for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data lower than predicted in Example 1C ..............................................................................................85  Figure 23. Benefit-cost analysis results for shoulder paving for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data lower than predicted in Example 1C ..............................................................................................85 

vi Figure 24. Benefit-cost analysis results for superelevation improvement for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data lower than predicted in Example 1C ....................................................................85  Figure 25. Entering site-specific crash data for Example 1C with site-specific crash history higher than predicted ....................................................................................................86  Figure 26. Benefit-cost analysis results for lane widening for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data lower than predicted in Example 1C ..............................................................................................86  Figure 27. Benefit-cost analysis results for shoulder paving for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data higher than predicted in Example 1C ..............................................................................................86  Figure 28. Benefit-cost analysis results for superelevation improvement for the rural two-lane highway with AADT of 8,600 veh/day with site-specific crash history data higher than predicted in Example 1C ...................................................................87  Figure 29. Roadway data input for a rural two-lane highway for Example 1D in Tool 2 ............88  Figure 30. Existing cross section data input for rural two-lane highway for Example 1D in Tool 2 .......................................................................................................................88  Figure 31. Alignment data input for rural two-lane highway for Example 1D in Tool 2 .............89  Figure 32. Specific curve data input for rural two-lane highway for Example 1D in Tool 2 .......89  Figure 33. Crash history input for rural two-lane highway for Example 1D in Tool 2 ................90  Figure 34. User selection of improvement alternatives to be considered in Tool 2 selected for rural two-lane highway in Example 1D .................................................................91  Figure 35. Roadway data input for rural four-lane highways in Example 3 .................................96  Figure 36. Existing cross section data input for rural four-lane highways in Example 3 .............96  Figure 37. Crash data input for rural four-lane highways in Example 3 .......................................96  Figure 38. Specific curve data for Example 3 ...............................................................................97  Figure 39. Alternatives to consider selection for the rural four-lane highway in Example 3 .......97  Figure 40. Project right-of-way cost inclusion option for the rural four-lane highways in Example 3 ....................................................................................................................97  Figure 41. Results of analysis for the rural four-lane highway in Example 3 ...............................98  Figure 42. Roadway data input for a freeway in Example 4 .......................................................101  Figure 43. Alignment option input for a freeway in Example 4 .................................................101  Figure 44. Average curve data input for a freeways in Example 4 .............................................101  Figure 45. Crash history option input for a freeway in Example 4 .............................................101  Figure 46. Existing cross section data input for a freeway in Example 4 ...................................102  Figure 47. Outside barrier count input for a freeway in Example 4 ............................................102  Figure 48. Outside barrier data input for a freeway in Example 4 ..............................................102  Figure 49. Data entry table for selecting alternatives to consider for a freeway in Example 4. .103  Figure 50. Right-of-way cost inclusion option for a freeway in Example 4. ..............................103  Figure 51. Benefit-cost analysis results for inside and outside shoulder widening for a freeway in Example 4 ................................................................................................103 

vii Tables Table 1. Example Crash Type Summary from Safety Analyst ...................................................12  Table 2. Traffic Operational Service Measures for Specific Roadway Facility Types .............15  Table 3. CMF for Lane Width on Rural Two-Lane Roadway Segments ..................................23  Table 4. CMF for Shoulder Width on Rural Two-Lane Roadway Segments ............................24  Table 5. CMFs for Shoulder Types and Shoulder Width on Roadway Segments (CMFtra) ......26  Table 6. Roadside Slope CMFs for Rural Two-Lane Highways ...............................................28  Table 7. CMFs for Installation of Left-Turn Lanes on Intersection Approaches ......................28  Table 8. CMFs for Installation of Right-Turn Lanes on Intersection Approaches ....................28  Table 9. CMF for Lane Width on Undivided Rural Multilane Roadway Segments ................29  Table 10. Roadside Slope CMFs for Rural Multilane Highways ................................................31  Table 11. CMFs for Installation of Left-Turn Lanes on Intersection Approaches ......................32  Table 12. CMFs for Installation of Right-Turn Lanes on Intersection Approaches ....................32  Table 13. CMF for Lane Width on Divided Rural Multilane Roadway Segment .......................32  Table 14. CMFs for Paved Right (Outside) Shoulder Width on Rural Multilane Divided Highway Segments ......................................................................................................33  Table 15. CMFs for Installation of Left-Turn Lanes on Intersection Approaches ......................35  Table 16. CMFs for Installation of Right-Turn Lanes on Intersection Approaches ....................35  Table 17. CMFs for Installation of Left-Turn Lanes on Intersection Approaches ......................37  Table 18. CMFs for Installation of Right-Turn Lanes on Intersection Approaches ....................37  Table 19. Coefficients for Inside Shoulder Width CMF on Freeways ........................................38  Table 20. Coefficients for Outside Paved Shoulder Width CMF on Freeways ...........................39  Table 21. Coefficients for Presence of Median Barrier CMF on Freeways ................................41  Table 22. Coefficients for Presence of Outside Barrier CMF on Freeways ................................42  Table 23. Coefficients for Median Width on Freeways ...............................................................42  Table 24. Minimum Lane and Shoulder Widths for Rural Two-Lane Highways from TRB Special Report 214 .......................................................................................................44  Table 25. Comprehensive Societal Costs of Crashes Recommended in the HSM ......................53  Table 26. Input Data for Safety Benefits Calculation Example ...................................................57  Table 27. CMFs for Example Roadway Section..........................................................................57  Table 28. Annual Crash Reduction by Severity Level Calculation .............................................60  Table 29. Example of Benefit-Cost Calculations for Lane Widening from 10 to 12 ft in Level Terrain on a Rural Two-Lane Highway .........................................................63  Table 30. Example of Benefit-Cost Calculations for Lane Widening from 9 to 10 ft in Level Terrain on a Rural Two-Lane Highway .........................................................63  Table 31. Example of Benefit-Cost Calculations for Lane Widening from 9 to 11 ft in Level Terrain on a Rural Two-Lane Highway .........................................................64  Table 32. Example of Benefit-Cost Calculations for Lane Widening from 9 to 12 ft in Level Terrain on a Rural Two-Lane Highway .........................................................64  Table 33. Example of Benefit-Cost Calculations for Lane Widening from 10 to 11 ft in Level Terrain on a Rural Two-Lane Highway .........................................................64  Table 34. Example of Benefit-Cost Calculations for Lane Widening from 11 to 12 ft in Level Terrain on a Rural Two-Lane Highway .........................................................65  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 .................67 

viii Table 36. Examples of Incremental Analysis to Determine Net Benefits of LaneWidening for Existing Rural Two-Lane Highways with 10-ft Lanes in Level Terrain ...............67  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 .........................................68  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 .............................68  Table 39. Existing Cross-Section Design and Other Existing Conditions for the Rural Two-Lane Highway in Example 1 ...............................................................................76  Table 40. Existing Horizontal Curve Geometrics for the Rural Two-Lane Highway in Example 1 ....................................................................................................................76  Table 41. Crash Frequencies Before and After Lane Widening for the Rural Two-Lane Highway with AADT of 2,000 veh/day in Example 1A .............................................79  Table 42. Crash Frequencies Before and After Lane Widening for the Rural Two-Lane Highway with AADT of 8,600 veh/day in Example 1A .............................................80  Table 43. Horizontal Curve Improved Superelevation Rates ......................................................82  Table 44. Minimum Green Book Superelevation Rates Provided by Tool 2 ..............................91  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 ...................................92  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 ...................................92  Table 47. Roadway Attributes for Rural Two-Lane Highway Considered in Example 2 ...........93  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 .......................................93  Table 49. Minimum AADT Levels at which Benefit-Cost Ratios Exceed 1.0 and 2.0 for Lane Widening for Example 2 ...............................................................................94  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 ............................................................................................94  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 ............................................................................................95  Table 52. Roadway Characteristics for Rural Four-Lane Undivided Highway in Example 3 ....95  Table 53. Specific Horizontal Curve Data for Example 3 ...........................................................96  Table 54. Results of Analysis for Shoulder Widening, Slope Flattening and Installing Shoulder Rumble Strips ...............................................................................................99  Table 55. Freeway Attributes for Example 4 .............................................................................100  Table 56. Outside Barrier Characteristics for Example Problem ...............................................100  Table 57. Before, After and Reduced Crash Frequencies on Freeway 3R Project in Example 4 ..................................................................................................................103 

ix Summary Introduction Resurfacing, restoration, and rehabilitation (3R) projects are typically initiated based on current or anticipated pavement conditions that indicate the need for pavement resurfacing. In designing 3R projects, highway agencies need to decide whether to simply resurface the pavement or whether to utilize the 3R project as an opportunity to implement other desirable improvements, such as geometric design changes, to reduce crash frequency and severity and/or improve traffic operations. The approach to such decisions recommended in these guidelines for application to specific 3R projects considers current roadway and roadside design, current and anticipated future traffic volumes, crash history and anticipated future crash frequency and severity, improvement implementation costs, and other economic, environmental, and community factors that highway agencies consider in the project development process. These guidelines provide a framework for considering these factors in 3R project design decisions, so that funds are invested in geometric design improvements as part of 3R projects primarily where documented crash patterns exist or where, in the absence of a documented crash pattern, the anticipated crash reduction benefits over the service life of the project exceed the improvement implementation costs. The guidelines advise highway agencies to avoid investing funds in geometric design improvements where the improvement implementation costs exceed the anticipated crash reduction benefits, unless there is either a documented crash pattern that can be mitigated by the improvements or a documented traffic operational improvement need. These guidelines are intended to replace the design guidelines for 3R projects presented in TRB Special Report 214, Designing Safer Roads: Practices for Resurfacing, Restoration, and Rehabilitation (1). The guidelines presented in this document are based on substantial advances in knowledge about the effects of geometric design features on crash frequency and severity since TRB Special Report 214 was published in 1987. Most specifically, the guidelines implement the safety knowledge presented in the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual (HSM) (2,3) and other recent safety research. Scope of Guidelines The scope of the guidelines is limited to projects involving only resurfacing, restoration, and/or rehabilitation. New construction and reconstruction projects are not addressed by these guidelines. The guidelines address 3R projects initiated for any reason. Most 3R projects are initiated because of poor pavement condition that indicates a need for pavement resurfacing, but the guidelines can also be applied to projects initiated for other reasons, as long as the project does not involve new construction or reconstruction.

x The guidelines address design of 3R projects on rural two-lane highways, rural multilane undivided highways, rural multilane divided nonfreeways, urban and suburban arterials, and rural and urban freeways. The guidelines are based on the current state of knowledge concerning crash reduction effectiveness and traffic operational improvements that can result from specific design alternatives for 3R projects. The guidelines should be updated in the future as knowledge of these issues advances. The guidelines are intended for application to 3R projects paid for from any funding source. Thus, the guidelines are not limited just to projects funded as part of the Federal 3R program. The guidelines are also applicable to 3R projects funded from other Federal sources and to projects funded entirely with state or local funds. The guidelines focus on deciding whether any specific project should be resurfaced without accompanying geometric design improvements or whether (and what) geometric design changes should be made as part of the project. The focus of the guidelines is entirely on determining the appropriate geometric design for the roadway after project implementation (either the same as the existing roadway or incorporating cost-effective changes). The guidelines do not address administrative issues such as the appropriate form of design approvals or the need for design exceptions. Such administrative issues are best addressed by the highway agencies involved. The highway community is moving toward more flexible geometric design processes, with reduced need for routine design exceptions, but such administrative issues are outside the scope of these guidelines. In any case, the cost-effectiveness approach utilized in these guidelines should provide the justification needed for design decisions within any administrative framework for design approval procedures that may be in place. How Does the Design Process for 3R Projects Differ from the Design Process for New Construction and Reconstruction Projects? The current design process for new construction projects is based primarily on the dimensional design criteria presented in the AASHTO Green Book (4) and in the design policies of individual highway agencies. It is appropriate to use established dimensional design criteria for new construction projects because, in such projects, there is no existing roadway with a safety and traffic operational performance history that can be used to guide the design process. Established dimensional design criteria provide an aspirational goal for design of reconstruction projects. Where a roadway is being fully reconstructed, design improvements may be feasible with limited additional cost, except where such improvements would substantially impact adjacent development, established communities, or sensitive environments; in these situations, highway agencies typically seek a design exception to minimize such impacts. 3R projects are usually initiated based on the need for pavement resurfacing and are most appropriately considered as maintenance activities. A performance-based design process provides the basis for design of 3R projects focusing on the decision about which projects should be resurfaced without accompanying design improvements and which projects should have design improvements incorporated.

xi The design process for 3R projects begins with the recognition that the project will be implemented on an existing road whose past safety and traffic operational performance is known and should serve as a key factor in design decisions. Unlike new construction and reconstruction projects, which are designed in accordance with dimensional design criteria presented in the AASHTO Green Book (4), these guidelines do not establish dimensional design criteria for 3R projects. Rather, 3R design decisions are based on an assessment of the safety and traffic operational performance of the existing road and the cost-effectiveness of potential design improvements. Geometric design improvements should be considered as part of a 3R project in the following situations:  An analysis of the crash history of the existing road identifies one or more crash patterns that are potentially correctable by a specific design improvement, or  An analysis of the traffic operational level of service (LOS) indicates that the LOS is currently lower than the highway agency’s target LOS for the facility or will become lower than the target LOS within the service life of the planned pavement resurfacing (typically 7 to 12 years), or  A design improvement would reduce sufficient crashes over its service life to be cost- effective; i.e., the anticipated crash reduction benefits over the service life of the project should exceed the improvement implementation cost. In the absence of any of the three situations defined above, there is no indication that a design improvement is needed as part of a 3R project, and the existing roadway and roadside geometric features should remain in place. It makes little sense to invest scarce resources in design improvements as part of a 3R project where the existing roadway is performing well and where potential design improvements would not be cost-effective; the funds needed for such a project can be better invested in projects that do have documented performance concerns or where potential design improvements would be cost-effective. In particular, improvement of systemwide safety across the road network is so important that funds invested with the objective of improving safety should be directed toward projects where it can be demonstrated that safety benefits will actually be obtained. The reliance on cost-effectiveness to guide design decisions for 3R projects has several advantages:  Highway agencies can have confidence that funds invested in design improvements intended to reduce crashes as part of 3R projects are, in fact, likely to result in reduced crashes.  Since crash frequency for a road generally increases with increasing traffic volume, the use of cost-effectiveness analysis as a basis for design decisions means that the likelihood of design improvements being included in a 3R project increases with increasing traffic volume. This dependence of design decisions on traffic volume levels is logical and desirable and is not fully reflected in most current dimensional design criteria for new construction and reconstruction.  A cost-effectiveness approach will focus improvement needs on low-cost improvements with documented safety effectiveness, which are most consistent with the limited scope

xii of 3R projects. However, the procedures are flexible enough that higher cost improvements can be considered where benefits are sufficient to justify their implementation. If extensive geometric improvements are found to be cost-effective, consideration may be given to reclassifying the project as a reconstruction project. The guidelines demonstrate that reliance on dimensional design criteria will result in suboptimal results, with some investments made at locations where they are not cost-effective and other investments not made at locations where they would be cost-effective. Crash Reduction Effectiveness of 3R Improvements The crash reduction effectiveness of design improvements that are commonly incorporated in 3R projects is documented in these guidelines based on crash modification factors (CMFs) presented in the AASHTO Highway Safety Manual (2,3) and recent research. Benefit-Cost Analysis Procedures The guidelines present a set of benefit-cost analysis procedures that can be applied to alternative geometric design improvements for 3R projects to determine which improvements would be cost-effective and which improvements would not be cost-effective. 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 Procedures for each of these applications are presented in Section 5.5 of these guidelines. Benefit-Cost Analysis Tools Two spreadsheet tools for benefit-cost analysis in support of 3R project design decisions are presented in these guidelines. These include a tool for analysis of a single design alternative or combination of alternatives (Spreadsheet Tool 1) and a tool for comparison of several design alternatives or combinations of alternatives (Spreadsheet Tool 2). The spreadsheet tools apply to rural two-lane highways, rural multilane nonfreeways (including both undivided and divided highways), and rural and urban freeways. The tools do not address urban and suburban arterials because no crash reduction effectiveness estimates are available for most project types on arterials. Examples of the application of each spreadsheet tool are presented in Section 5.7 of these guidelines. User guides for the spreadsheet tools are presented in Appendices A and B.

xiii 3R Project Design Guidelines for Specific Roadway Types General design guidelines applicable to all 3R projects are presented in Chapters 2 through 5, including an introduction to the spreadsheet benefit-cost analysis tools in Chapter 5. Specific design guidelines in Chapter 6 are presented for 3R projects on the roadway types to which the spreadsheet benefit-cost analysis tools apply, as well as for urban and suburban arterials. The specific types of 3R project improvements addressed by the guidelines include lane widening, shoulder widening and paving, horizontal curve improvements, sight distance improvements, bridge widening, passing lanes, restoration of normal pavement cross slope, rumble strip improvements, striping and delineation improvements, roadside slope flattening, removal of roadside objects, installation/rehabilitation of guardrail and other traffic barriers, intersection turn lane improvements, and other intersection improvements. A summary of the guidelines is presented in Chapter 7.

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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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