A Performance-Based Highway Geometric Design Process (2016)

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2017 N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP RESEARCH REPORT 839 A Performance-Based Highway Geometric Design Process Timothy R. Neuman Bednar Consulting llC Johnstown, OH Richard C. Coakley Srikanth Panguluri CH2M Chicago, IL Douglas W. Harwood MrigloBal Kansas, MO Subscriber Categories Design Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research is the most effective way to solve many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation results in increasingly complex problems of wide inter- est to highway authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. TRB is uniquely suited for this purpose for many reasons: TRB maintains an extensive com- mittee structure from which authorities on any highway transportation subject may be drawn; TRB possesses avenues of communications and cooperation with federal, state, and local governmental agencies, univer- sities, and industry; TRB’s relationship to the Academies is an insurance of objectivity; and TRB maintains a full-time staff of specialists in high- way transportation matters to bring the findings of research directly to those in a position to use them. The program is developed on the basis of research needs identified by chief administrators and other staff of the highway and transporta- tion departments and by committees of AASHTO. Topics of the highest merit are selected by the AASHTO Standing Committee on Research (SCOR), and each year SCOR’s recommendations are proposed to the AASHTO Board of Directors and the Academies. Research projects to address these topics are defined by NCHRP, and qualified research agencies are selected from submitted proposals. Administration and surveillance of research contracts are the responsibilities of the Acad- emies and TRB. The needs for highway research are many, and NCHRP can make significant contributions to solving highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement, rather than to substitute for or duplicate, other highway research programs. Published research reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 839 Project 15-47 ISSN 0077-5614 ISBN 978-0-309-44627-3 Library of Congress Control Number 2017934610 © 2017 National Academy of Sciences. All rights reserved. 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 TRB, AASHTO, FAA, FHWA, FMCSA, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC endorsement 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. NOTICE The research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and 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 of Sciences, Engineering, and Medicine; 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.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. C. D. Mote, Jr., is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied committees, task forces, and panels annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individuals interested in the development of transportation. Learn more about the Transportation Research Board at www.TRB.org.

C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 15-47 by CH2M, Midwest Research Institute (MRI) Global, and Bednar Consulting LLC. CH2M was the contractor for this study, with MRIGlobal and Bednar Consulting LLC as subcontractors. Richard Coakley at CH2M served as the Co-Principal Investigator, Srikanth Panguluri, P.E., at CH2M served as the Project Manager, and Timothy R. Neuman served as the Principal Investigator previously employed at CH2M and currently at Bednar Consulting LLC. The other authors of this report are Ms. Ingrid B. Potts at MRIGlobal, Mr. Douglas W. Harwood at MRIGlobal, Ms. Jessica M. Hutton at MRIGlobal, Mr. Daniel J. Cook at MRIGlobal, Andrew Ardrey at CH2M, and Richard Storm previously employed at CH2M. The work was done under the general supervision of Richard Coakley and Timothy R. Neuman. CRP STAFF FOR NCHRP RESEARCH REPORT 839 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs B. Ray Derr, Senior Program Officer Charlotte Thomas, Senior Program Assistant Eileen P. Delaney, Director of Publications Scott E. Hitchcock, Editor NCHRP PROJECT 15-47 PANEL Area of Design—Field of General Design Barton A. Thrasher, Virginia DOT, Richmond, VA (Chair) Deanna Lynn Maifield, Iowa DOT, Ames, IA Anthony J. Buczek, METRO, Portland, OR Daniel M. Dulaski, Northeastern University, Boston, MA James L. Gattis II, University of Arkansas—Fayetteville, Fayetteville, AR Peter C. Martin, CDM Smith, San Francisco, CA Hugh W. McGee, Vienna, VA Dennis R. Toomey, Pennsylvania DOT, Allentown, PA Dale Widner, California DOT, Redding, CA Brooke Struve, FHWA Liaison Stephen F. Maher, TRB Liaison

NCHRP Research Report 839: A Performance-Based Highway Geometric Design Process presents a new process for highway geometric design that is more aligned with current expectations of transportation agencies and their communities and makes full use of the tools available to them. The report reviews the evolution of highway design, presents several key principles for today’s design challenges, recommends a new highway geometric design process, and demonstrates the value of the process through six illustrative case studies. The new process focuses on the transportation performance of the design rather than the selection of values from tables of dimensions applied across the range of facility types. The report will be valuable to senior staff in transportation agencies as they consider changes to their design processes and to AASHTO in the development of future editions of A Policy on Geometric Design of Highways and Streets (the Green Book). The design of a highway—its three-dimensional features (horizontal alignment, vertical alignment, and cross-section) and appurtenances to provide for drainage, traffic control, and safety—requires a well-defined process. AASHTO and its predecessor, AASHO, have published highway design policy since the 1940s; the underlying highway design process has remained essentially unchanged since that time. During the past 75 years, transportation needs have evolved and much has been learned about the relationships among geometric design, vehicle fleet, human factors, safety, and operations. AASHTO has continually updated its policies to respond to these changes, but the fundamental design process and basic design approaches have remained fairly constant. Some agencies have begun using an expanded array of roadway functional classifications as a basis for selecting certain design criteria. An assessment of the current design process is needed to ensure that recent advances in knowledge (e.g., the AASHTO Highway Safety Man- ual) and emerging issues (e.g., complete streets, flexible design) are appropriately addressed. In NCHRP Project 15-47, CH2M, Bednar Consulting LLC, and MRIGlobal reviewed the relevant literature and coordinated with AASHTO and TRB committees to explore alternative design processes. They developed findings on the current design process and formulated guiding principles for a new performance-based process. After meeting with the panel, the research team laid out a comprehensive approach to design and illustrated how it could be applied in six illustrative case studies. Further research to fully implement the revised process was also described. While it is not a design manual, the AASHTO Green Book is a comprehensive reference that designers use in considering various design alternatives and it underlies state and local design manuals. This report examines how a future edition of the Green Book could best support a performance-based design process. F O R E W O R D By B. Ray Derr Staff Officer Transportation Research Board

Readers of this report will also be interested in the results of the following NCHRP projects that complement this report: • NCHRP 15-50, “Guidelines for Integrating Safety and Cost Effectiveness into Resurfacing, Restoration, and Rehabilitation Projects” and • NCHRP 15-52, “Developing a Context-Sensitive Functional Classification System for More Flexibility in Geometric Design.”

1 Summary 3 Chapter 1 Introduction 5 Chapter 2 The Evolution of Highway Design in the U.S. 5 2.1 Up to the 1940s 6 2.2 The 1950s—The Technology of Highway Planning and Design Addresses Burgeoning Mobility Needs and National Public Policy Advances 6 2.3 The 1960s—The Growth of the Interstate System and Urban Transportation 7 2.4 The 1970s—Environmental Initiatives Drive National Transportation Policy and Programs 7 2.5 The 1980s—Transportation Professionals Wrestle with Reconstruction Needs and Congestion as Emerging Issues 8 2.6 The 1990s—Unsolved Problems of Congestion, Project Development, Community Sensitivity, and Funding Begin to Take Their Toll 9 2.7 The 2000s to the Present Day—The Need for a New Highway Design Paradigm Is Recognized 10 2.8 Recent Advances in Highway Design 10 2.8.1 Introduction 22 2.8.2 History and Evolution of the Highway Industry 25 Chapter 3 Highway Geometric Design and Project Development 25 3.1 Introduction 25 3.1.1 Highway Design Decision Making 27 3.1.2 Transportation Values Addressed by the Process 28 3.1.3 Objective of the Design Process 29 3.1.4 The Legal Framework in Which the Road and Highway Design Process Exists 31 3.2 Key Findings on the Highway Design Development Process and Need for Design Process Changes 31 3.2.1 Finding 1: Interdisciplinary Project Development Is Here to Stay (Institutionalization of CSS) 32 3.2.2 Finding 2: Context Matters—And It Varies 36 3.2.3 Finding 3: Providing Multimodal Solutions Is Now the Rule and Not the Exception 36 3.2.4 Finding 4: AASHTO Dimensional Criteria Should Ideally Be Based on Known and Proven Measurable Performance Effects 37 3.2.5 Finding 5: Speed Is an Essential Input to Determination of Design Values and Dimensions 38 3.2.6 Finding 6: AASHTO Design Criteria Produce Uneven Outcomes Re: Performance C O N T E N T S

38 3.2.7 Finding 7: Many AASHTO Criteria Are Not Sensitive to Key Context Attributes That Are Proven Influencers of Performance and Cost Effectiveness 40 3.2.8 Finding 8: Some AASHTO Criteria Are Unnecessarily Simplistic in Their Formulation, or Are Based on Models That Are Lacking a Proven Science Basis 41 3.2.9 Finding 9: The Legal Framework Requires the Provision of Threshold Limits for Design Criteria and Design Values; the Question Is—How Should Such Lower Limits Be Set? 42 3.2.10 Finding 10: Nominal and Substantive Safety Differ in Meaningful Ways 43 3.2.11 Finding 11: AASHTO Criteria Should More Completely Reflect Known Interactive Safety and Operational Effects of Geometry 44 3.2.12 Finding 12: Replace Dimensional Guidance with Direct Perfor- mance Guidance Where Possible Within the AASHTO Policy 45 3.2.13 Finding 13: Advances in Technology Should Be Incorporated into the Geometric Design Process 47 3.2.14 Finding 14: The Notion of “Conservatism” in Policy and Leader- ship in the Highway Engineering Field Needs a 180 Degree Shift 48 3.2.15 Finding 15: Geometric Design Should Be Understood, Taught, Executed, and Communicated as Iterative in Nature with Performance at the Center of All Iterations and Optimizing 48 3.2.16 Finding 16: More Explicitly Incorporate Maintenance and Operation Costs 49 Chapter 4 Guiding Principles for an Effective 21st Century Highway Design Process 49 4.1 Fundamental Bases for Roadway Design 49 4.1.1 Geometric Design Solutions Should Address Objective, Quantitative Measures of Transportation Performance 51 4.1.2 The Geometric Design Process Should Explicitly Address All Potential, Legal Road Users 52 4.1.3 The Geometric Design Process Should Integrate Operational Solutions with Geometric Elements 54 4.1.4 The Design Process Is Forward Looking 55 4.1.5 The Design Process Must Be Context Sensitive to the Extent Possible 56 4.1.6 The Design Process Must Be Financially Sustainable at Both the Program and Project Level 56 4.2 The Design Process Must Be Conducted Within the Prevailing Social and Public Policy Framework 57 4.2.1 Accountability and Responsibility 58 4.2.2 Legal Framework 64 4.2.3 The Design Process Should Support the Financial Sustainability of the Agency’s Program 65 4.3 Attributes of an Effective Geometric Design Process 66 4.3.1 Efficiency 67 4.3.2 Scalability 67 4.3.3 Executable 67 4.3.4 Transparency and Defensibility

68 Chapter 5 Performance-Based Highway Design Process 68 5.1 Step 1—Define the Transportation Problem or Need 70 5.2 Step 2—Identify and Charter All Project Stakeholders 71 5.2.1 Internal Agency Stakeholders 71 5.2.2 External Agency Stakeholders 71 5.2.3 Other External Stakeholder Groups or Agencies 71 5.2.4 Directly Affected Stakeholders 72 5.2.5 Stakeholder Chartering 72 5.3 Step 3—Develop the Project Scope 72 5.3.1 Refinement and Confirmation of Problem or Needs Statement 73 5.4 Step 4—Determine the Project Type and Design Development Parameters 74 5.4.1 Unique Characteristics of New Roads 74 5.4.2 Unique Characteristics of Reconstruction Projects 76 5.4.3 Unique Characteristics of 3R Projects 76 5.4.4 Project Types and Transportation Problems 77 5.4.5 Setting of Project Limits and Major Study Parameters or Controls 77 5.4.6 Determining Environmental Process and Documentation Requirements 78 5.4.7 Establishment of Planning Level Implementation Budget 78 5.5 Step 5—Establish the Project’s Context and Geometric Design Framework 78 5.5.1 Framework for Geometric Design Process—New Construction and Reconstruction 90 5.5.2 Develop Project Evaluation Criteria Within the Context Framework 92 5.5.3 Establish Decision-making Roles and Responsibilities 92 5.5.4 Determine Basic Geometric Design Controls—Design or Target Speed 95 5.5.5 Determine Basic Design Controls—Design Traffic Volumes 99 5.5.6 Determine Basic Design Controls—Design LOS (or Operating Condition) 100 5.5.7 Determine Basic Design Controls—Road User Attributes 102 5.6 Step 6—Apply the Appropriate Geometric Design Process and Criteria 103 5.6.1 Roads on New Alignment Are Designed with a Unique Process and Criteria 103 5.6.2 Design of Projects Involving Existing Roads 108 5.6.3 Develop Project Technical Approach 108 5.7 Step 7—Designing the Geometric Alternatives 108 5.7.1 Assemble an Inclusive and Interdisciplinary Team 109 5.7.2 Focus on and Address the Need or Solve the Problem(s) Within the Context Conditions and Constraints 114 5.8 Step 8—Design Decision Making and Documentation 114 5.8.1 Independent Quality and Risk Management Processes 117 5.9 Step 9—Transition to Preliminary and Final Engineering 118 5.9.1 Technology Applications—Building Information Modeling 121 5.10 Step 10—Agency Operations and Maintenance Database Assembly 121 5.11 Step 11—Continuous Monitoring and Feedback to Agency Processes and Database 123 Chapter 6 Updating the Technical Guidance on Geometric Design in the AASHTO Policies 123 6.1 Overview of Contents of 2011 AASHTO Policy on Geometric Design 125 6.2 Lane and Traveled Way Widths

127 6.3 Shoulder Widths 129 6.3.1 Framework for Design Criteria Development— Lane Width and Shoulders 130 6.3.2 Local Roads in Rural Contexts 130 6.3.3 Collector Roads and Arterials in Rural Contexts 130 6.3.4 Urban Nonfreeway Roads 130 6.3.5 Urban Freeways 131 6.4 Roadside Design 131 6.5 Alignment and Sight Distance 132 6.5.1 Horizontal Curvature 141 6.5.2 Summary of Revised Approach to Horizontal Curve Design 142 6.6 Sight Distance 142 6.6.1 Critique of AASHTO Sight-Distance Design Policy and Models 145 6.6.2 Potential Approaches to Sight-Distance Design Policy 147 6.7 Vertical Alignment 147 6.7.1 Grade 149 6.7.2 Crest Vertical Curvature 152 6.8 Vertical Clearance 152 6.9 Medians and Access Control 154 Chapter 7 Value and Benefits of Improved Process 154 7.1 Introduction 155 7.2 Case Studies 155 7.2.1 Case Study 1: Addition of a Bicycle Lane on an Urban Arterial 158 7.2.2 Case Study 2: Addition of a Freeway Entrance Loop Ramp to a Diamond Interchange 164 7.2.3 Case Study 3: Reconstruction (or 3R) Project on a Rural Two-Lane Highway 167 7.2.4 Case Study 4: Proposed Bypass Around a Small Community 176 7.2.5 Case Study 5 178 7.2.6 Case Study 6 181 Chapter 8 Research and Knowledge Needs to Fully Implement the Revised Process 181 8.1 AASHTO Curve Model 181 8.2 AASHTO SSD Model 182 8.3 O&M Understanding Related to Geometric Design Elements 182 Further Research and Study 182 8.4 Challenges with New Process 183 8.4.1 Summary of Potential Design Processes 184 8.4.2 Challenges to Implementing a Revised Geometric Design Process 184 8.4.3 Organizational and Institutional 185 8.4.4 Risk Management 185 8.4.5 Scalability for Owner, Roadway, and Project Size 186 8.4.6 Professional 186 8.4.7 A State’s Experience Implementing a Flexible Design Process 187 8.4.8 Lessons Learned from Recent Process Changes 188 8.5 Green Book Reorganization 189 8.5.1 A Future Generation AASHTO Policy on Geometric Design 190 8.6 Implications with Driverless/Connected/Autonomous Technology

192 Works Cited and Bibliography 195 Acronyms and Abbreviations A-1 Appendix A Example Performance Criteria Memorandum B-1 Appendix B Review of the 2011 AASHTO Policy on Geometric Design C-1 Appendix C Horizontal Curve Analysis D-1 Appendix D Operations and Maintenance Considerations for Geometric Design E-1 Appendix E The Future AASHTO Green Book