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2018 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 880 Design Guide for Low-Speed Multimodal Roadways Marshall Elizer Jay Bockisch Michael Sewell Gresham, smith and Partners Nashville, TN Ingrid Potts Darren Torbic midwest research institute Kansas City, MO Joe Gilpin alta PlanninG and desiGn Bozeman, MT Subscriber Categories Pedestrians and Bicyclists â¢ 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 techniquesâthe 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 TRBâs 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; TRBâs relationship to the National Academies is an insurance of objectivity; and TRB maintains a full-time staff of special- ists in highway 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 transportation departments, by committees of AASHTO, and by the Federal Highway Administration. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&Iâs recommendations are proposed to the AASHTO Board of Direc- tors and the National 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 National Academies 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 880 Project 15-48 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-39051-4 Library of Congress Control Number 2018949132 Â© 2018 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 manufacturersâ names appear herein solely because they are considered essential to the object of the report. Photos/images in the following exhibits are used by permission: Exhibit 5-12 courtesy of Community Design + Architecture; Figure 5-19 courtesy of FloridaBicycle.org; and Figure 5-20 courtesy of TrailLink.
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 National 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 Boardâs 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 CRP STAFF FOR NCHRP RESEARCH REPORT 880 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Senior Program Officer Megan A. Chamberlain, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Sharon Lamberton, Editor NCHRP PROJECT 15-48 PANEL Field of DesignâGeneral Design Brent A. Story, Georgia DOT, Atlanta, GA (Chair) Stanley W. Wood, Ipswich, MA Anne M. Benware, Capital District Transportation Committee, Albany, NY G. David Hutchison, Springfield (MO) Public Works Department, Springfield, MO Yanxiao Jia, Iowa DOT, Ames, IA Michael Robert King, Nelson\Nygaard Consulting Associates, New York, NY Brian Ho-Yin Lee, Puget Sound Regional Council, Seattle, WA Richard C. Moeur, Moeurgineering, PLLC, Phoenix, AZ Keith J. Harrison, FHWA Liaison Bernardo Kleiner, TRB Liaison
NCHRP Research Report 880: Design Guide for Low-Speed Multimodal Roadways (1) pro- vides best practice guidance to the designer by referencing a range of acceptable elements, criteria and values for critical dimensions for design of low- to intermediate-speed (45 mph and lower design speed) roadways with a mix of users and (2) assists designers in establish- ing a balance between operational efficiency, comfort, safety, and convenience for modes on the low- and intermediate-speed roadways. The report also includes detailed design case studies of design processes. The material in this report will be of immediate interest to design practitioners and stakeholders involved in the planning and design of streets and roadways that serve a mix of motorized and non-motorized users on facilities designed for low and intermediate speeds. There is increasing recognition that successful roadway geometric design must provide an appropriate balance of service and safety for all users, including the consideration of cyclist and pedestrian users, and be coordinated with the uses and âcontextâ of adjacent properties. The 2011 AASHTO A Policy on Geometric Design of Highways and Streets (the Green Book) recognizes this need, but provides limited specific guidance on how to incorporate this balance in the roadway design process. Little established practical engineering design guidance exists on how to effectively integrate and balance the service to all transportation modes along the same facility, corridor, or intersection. Most available geometric design guidance is based upon design for a single mode and does not fully address or incorporate the often competing needs of other modes requiring attention. For example, because of the vulnerability of pedestrians and cyclists, they are involved in a disproportionate number of serious injury and fatal collisions at intersections. Factors that include a roadway functional classification, roadway operating speed, current and pro- jected user demand, adjacent context, and community goals present a challenge in creating geometric designs that adequately recognize and provide for a mix of transportation modes and trip types, and reflect the priority that each should be given. This can be particularly difficult for certain intermediate-speed situations, which present a combination of multi- modal features that may not integrate well or be congruent with each other. The design process should apply to roadways of all types, but particularly those in an environment of limited right-of-way, congested traffic conditions, and other routine multimodal design challenges. In addition, there was a need for a methodology for optimizing the balance of tradeoffs between geometric design elements and safety and operational performance for all users of these facilities. F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board
Under NCHRP Project 15-48, Gresham, Smith and Partners was asked to develop a set of integrated guidelines that will help designers accommodate all users in the design of low- and intermediate-speed roadways, including: â¢ Methods to identify the mix of users that need to be served on various roadway functional classifications (context, area types, etc.) and speed categories (low and intermediate speeds); â¢ Methodologies supported by empirically based research and best practices that can balance and optimize how geometric design elements provide for safe and effective operation; â¢ Geometric design parameters for the types and designs of facilities to serve all users, and â¢ Examples showing how facilities representing various roadway functional classifications and speed categories have been or could be designed effectively. In addition to the guidelines published as NCHRP Report 880, the research agencyâs final report that documents the entire research effort is available on the web page for NCHRP Project 15-48 at the TRB website (http://apps.trb.org/cmsfeed/TRBNetProjectDisplay6.asp? ProjectID=3416).
1 Summary 3 Chapter 1 Introduction 3 1.1 Purpose, Objectives and Organization of the Guide 5 1.2 Intended Users 6 1.3 Range of Facilities Addressed 7 1.4 Project Development and Design Process to Address All Users 7 1.5 Applicability 8 1.6 Relationship to Other Design Guidance 10 Chapter 2 Design Considerations for All Users in Low- and Intermediate-Speed Environments 10 2.1 Design Controls, Criteria and Elements 11 2.2 Conventional Versus Evolving Roadway Design Practice 15 2.3 Roadway User Definitions and Characteristics 17 2.4 Functional System Considerations 18 2.5 Functional Classification and Urban Roadway Terminology 20 2.6 Modes: Separation, Integration and Conflict Reduction 21 2.7 Understanding and Assessing Context 23 2.8 Context-Sensitive Design Principles 24 2.9 Relationship of Design Elements to Context 26 2.10 Relationship of Design, Operating and Posted Speed to Context 28 2.11 Speed Management as a Design Goal 30 2.12 Flexibility in Application of Design Elements and Criteria 32 2.13 Design Exceptions 34 2.14 Liability Considerations 35 2.15 Considerations for Users with Disabilities 37 2.16 Considerations for Bridges and Other Structures 38 2.17 Coordination with Stormwater and Green Infrastructure 40 Chapter 3 Balancing User Performance in Low- and Intermediate-Speed Environments 40 3.1 Performance for Multimodal Projects 41 3.2 Assessing Performance, LOS and QOS for All Users 49 3.3 Design Volumes and Design Years 53 3.4 Recommended Minimum Multimodal Accommodation 55 3.5 Relationships between Geometric Design and Performance of All Users 63 3.6 Multimodal Project Design Development Process 72 3.7 Balancing MMLOS 74 3.8 Design Process in Constrained Rights-of-Way C O N T E N T S
76 Chapter 4 Traveled Way Design Guidelines 76 4.1 General Considerations for Traveled Way Design for All Users 92 4.2 Traveled Way Design Element Guidelines for All Users 147 4.3 Other Design Considerations for All Users in Traveled Way Design 171 Chapter 5 Roadside Design Guidelines 171 5.1 General Considerations 193 5.2 Roadside Design Guidelines 233 Chapter 6 Case Studies: Designing for All Users 233 6.1 Introduction 234 6.2 Design Case Study A: Creating a Retail-Oriented Main Street 239 6.3 Design Case Study B: Cascade Avenue 249 6.4 Design Case Study C: High-Capacity Thoroughfare in Urbanizing Area 255 6.5 Design Case Study D: 27th Avenue 265 References and Bibliography Note: Photographs, figures, and tables in this report may have been converted from color to grayscale for printing. The electronic version of the report (posted on the web at www.trb.org) retains the color versions.