National Academies Press: OpenBook
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2012. Human Factors Guidelines for Road Systems: Second Edition. Washington, DC: The National Academies Press. doi: 10.17226/22706.
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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2012 www.TRB.org 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 REPORT 600 Subscriber Categories Design • Safety and Human Factors Human Factors Guidelines for Road Systems Second Edition John L. Campbell Monica G. Lichty James L. Brown Christian M. Richard Justin S. Graving BATTELLE Seattle, WA Jerry Graham Mitchell O’Laughlin Darren Torbic Douglas Harwood MIDWEST RESEARCH INSTITUTE Kansas City, MO 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 provides the most effective approach to the solution of 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 develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Board’s recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of 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 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 at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 600D Project 17-47 ISSN 0077-5614 ISBN 978-0-309-25816-6 Library of Congress Control Number 2012940787 © 2012 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, FTA, or Transit Development Corporation 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 project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The 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 Governing Board of the National Research Council. 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 Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, 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 is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy’s purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide 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 activities 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 individu- als interested in the development of transportation. www.TRB.org www.national-academies.org

CRP STAFF FOR NCHRP REPORT 600, SECOND EDITION Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Mark S. Bush, Senior Program Officer Charles W. Niessner, Senior Program Officer (retired) Andrea Harrell, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Senior Editor NCHRP PROJECTS 17-31, 17-41, AND 17-47 PANELS Field of Traffic—Area of Safety Thomas Hicks, Maryland State Highway Administration, Hanover, MD (Chair) Larry Christianson, Deja Program Development, Merlin, OR Maurice R. Masliah, HDR Inc., Richmond Hill, ON Joseph V. Mondillo, Federal Highway Administration, Albany, NY David K. Olson, Washington State DOT, Olympia, WA Wendel T. Ruff, ABMB Engineers, Inc., Jackson, MS Leo Tasca, Ontario Ministry of Transportation, Downsview, ON (17-31 and 17-41 only) Samuel C. Tignor, Virginia Polytechnic Institute and State University, McLean, VA Thomas Granda, FHWA Liaison (17-31 and 17-41 only) Christopher Monk, FHWA Liaison (17-47 only) Richard Pain, TRB Liaison 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 authors of this report have been fortunate to have had the support of a Project Working Group to assist in the development of the HFG. The authors are grateful for the help of the Project Working Group members, who have provided valuable insights and feedback on relevant literature, end-user require- ments, and both draft and final guidelines throughout the HFG’s development process. Their willingness to share their time and expertise is deeply appreciated and has greatly improved the quality and value of the HFG. The following Project Working Group members provided review and comments during one or more of the phases of this project: Darin Bowman Derek Christianson Mike Crow Dave Daubert Rick Glad Fred Hanscom Jeff Jones Ken Kobetsky Kevin Lacy Joel Marcuson Mike McClain Emmett McDevitt George Merritt Jim Pline Fred Ranck James Rosenow Dan Sprengler Larry Sutherland Sophia Vardaki Ida van Schalkwyk

This report completes and updates the first edition of NCHRP Report 600: Human Fac- tors Guidelines for Road Systems (HFG), which was published previously in three collections. The HFG contains guidelines that provide human factors principles and findings for con- sideration by, and is a resource document for, highway designers, traffic engineers, and other safety practitioners. Each of the design guidelines in the HFG is presented using a con- sistent, highly structured format that is intended to maximize ease-of-use and interpretabil- ity. The guidelines focus on providing specific, actionable design principles, supported by a discussion and review of key research and analyses. Special design issues and considerations are included to help address design constraints and relevant trade-offs. The TRB, AASHTO, and the FHWA have been working since 2001 on successive and complementary projects that together help promote increased safety for all road users. The results of these efforts are the Highway Safety Manual (HSM) and the Human Factors Guide- lines for Road Systems (HFG). From 2008 through 2010, various completed chapters of the HFG were published in three collections; this report concludes the last project, includes the remaining chapters, and provides the entire compilation as a new holistic publication. These projects have been supported by funding from NCHRP and the FHWA. The HSM and the HFG promote improved safety for highway users and complement each other. While the HSM includes one section of a chapter on human factors, it provides only a broad scope and not guidelines. Each should be used together; however, neither document is a substi- tute for national or state standards such as A Policy on Geometric Design of Highways and Streets (the AASHTO Green Book) or the Manual on Uniform Traffic Control Devices (MUTCD). The HSM provides highway engineers with a synthesis of validated highway research and proven procedures for integrating safety into both new and improvement projects. It also provides practitioners with enhanced analytic tools for predicting and measuring the suc- cess of implemented safety countermeasures. The HSM can be used to develop possible design alternatives to improve safety on an in-service or planned intersection or section of roadway; the HFG can be used concurrently to identify design solutions or to enhance the alternatives suggested by the HSM. The HFG is a new roadway design resource that provides data and insights from the scientific literature on the needs, capabilities, and limitations of road users, including perception and effects of visual demands, cognition and influence of expectancies on driving behavior, and individual differences including age and other factors. The HFG provides guidance for roadway location elements (e.g., curves, grades, intersections, construction/work zones, rail-highway grade crossings) and traffic engineering elements F O R E W O R D By Mark S. Bush Staff Officer Transportation Research Board

NOTES ON PUBLICATION OF HUMAN FACTORS GUIDELINES FOR ROAD SYSTEMS, SECOND EDITION The first edition of NCHRP Report 600: Human Factors Guidelines for Road Systems was published in three collections from March 2008 to July 2010. This self-contained second edition contains new Chapters 7, 8, 9, 12, 14, 15, 21, and 27 and minor updates to the remaining chapters. Chapter 3 (Finding Information Like a Road User) and Chapter 4 (Integrating Road User, Highway Design, and Traffic Engineering Needs) are authored by Samuel Tignor, Thomas Hicks, and Joseph Mondillo. Chapter 5 (Sight Distance Guidelines) and Tutorials 1 and 2 in Chapter 22 (Tutorials) present a revision of materials originally published as NCHRP Web-Only Document 70: Comprehensive Human Factors Guidelines for Road Systems (2004), N. Lerner, R. Llaneras, A. Smiley, and F. Hanscom, Washington, DC: Transportation Research Board. (e.g., signing, changeable message signs, markings, and lighting). In addition, the HFG provides tutorials on special design topics, an index, and a glossary of technical terms. Successful highway safety depends on the consideration and integration of three funda- mental components—the roadway, the vehicle, and the roadway user. Unfortunately, many traditional resources used by practitioners lack data on the information needs, limitations, and capabilities of roadway users. Because driver error is a key contributor to driving crashes and road fatalities, a more driver-centered approach to highway design and operation will promote improved highway safety. The easy-to-use guidelines in the HFG provide the high- way designer and traffic engineer with objective, defensible human factors principles and information that can be used to support and justify design decisions. To this end, the HFG is a valuable tool in providing information about how road users operate in the driving envi- ronment. There is great value in bringing road users’ needs, capabilities, and limitations in to roadway design and traffic engineering.

P A R T I Introduction 1-1 Chapter 1 Why Have Human Factors Guidelines for Road Systems? 1-1 1.1 Purpose of Human Factors Guidelines for Road Systems 1-1 1.2 Overview of the HFG 2-1 Chapter 2 How to Use This Document 2-1 2.1 Organization of the HFG 2-1 2.2 Scope and Limitations of the HFG 2-2 2.3 The Two-Page Format 2-5 2.4 Tutorials 2-5 2.5 Other Features P A R T I I Bringing Road User Capabilities into Highway Design and Traffic Engineering Practice 3-1 Chapter 3 Finding Information Like a Road User 3-1 3.1 Introduction 3-1 3.2 Road User as a Component of the Highway System 3-2 3.3 Example Problems of Highway Designers and Traffic Engineers 3-4 3.4 How Road Users Seek Information 3-5 3.5 Examples of User-Scanned Road Environments 3-6 3.6 How Highway Designers and Traffic Engineers Work Together for Road Users 4-1 Chapter 4 Integrating Road User, Highway Design, and Traffic Engineering Needs 4-1 4.1 Introduction 4-1 4.2 Iterative Review Steps to Achieve Good Human Factor Applications 4-4 4.3 Use of Parts III and IV for Specifying Designs C O N T E N T S * * See “Notes on Publication of Human Factors Guidelines for Road Systems, Second Edition” on facing page.

P A R T I I I Human Factors Guidance for Roadway Location Elements 5-1 Chapter 5 Sight Distance Guidelines 5-2 Key Components of Sight Distance 5-4 Determining Stopping Sight Distance 5-6 Determining Intersection Sight Distance 5-8 Determining When to Use Decision Sight Distance 5-10 Determining Passing Sight Distance 5-12 Influence of Speed on Sight Distance 5-14 Key References for Sight Distance Information 5-16 Where to Find Sight Distance Information for Specific Roadway Features 5-18 Where to Find Sight Distance Information for Intersections 6-1 Chapter 6 Curves (Horizontal Alignment) 6-2 Task Analysis of Curve Driving 6-4 The Influence of Perceptual Factors on Curve Driving 6-6 Speed Selection on Horizontal Curves 6-8 Countermeasures for Improving Steering and Vehicle Control Through Curves 6-10 Countermeasures to Improve Pavement Delineation 6-12 Signs on Horizontal Curves 7-1 Chapter 7 Grades (Vertical Alignment) 7-2 Design Considerations for Turnouts on Grades 7-4 Geometric and Signing Considerations to Support Effective Use of Truck Escape Ramps 7-6 Preview Sight Distance and Grade Perception at Vertical Curves 8-1 Chapter 8 Tangent Sections and Roadside (Cross Section) 8-2 Task Analysis of Lane Changes on Tangent Sections 8-4 Overview of Driver Alertness on Long Tangent Sections 9-1 Chapter 9 Transition Zones Between Varying Road Designs 9-2 Perceptual and Physical Elements to Support Rural-Urban Transitions 10-1 Chapter 10 Non-Signalized Intersections 10-2 Acceptable Gap Distance 10-4 Factors Affecting Acceptable Gap 10-6 Sight Distance at Left-Skewed Intersections 10-8 Sight Distance at Right-Skewed Intersections 10-10 Countermeasures for Improving Accessibility for Vision-Impaired Pedestrians at Roundabouts 11-1 Chapter 11 Signalized Intersections 11-2 Engineering Countermeasures to Reduce Red Light Running 11-4 Restricting Right Turns on Red to Address Pedestrian Safety 11-6 Heuristics for Selecting the Yellow Timing Interval 11-8 Countermeasures for Improving Accessibility for Vision-Impaired Pedestrians at Signalized Intersections 12-1 Chapter 12 Interchanges 12-2 Task Analysis of Driver Merging Behavior at Freeway Entrance Ramps 12-4 Reducing Wrong-Way Entries onto Freeway Exit Ramps

12-6 Driver Expectations at Freeway Lane Drops and Lane Reductions 12-8 Driver Information Needs at Complex Interchanges 12-10 Arrow-per-Lane Sign Design to Support Driver Navigation 12-12 Driver Behavioral Trends Based on Exit Ramp Geometry 13-1 Chapter 13 Construction and Work Zones 13-2 Overview of Work Zone Crashes 13-4 Procedures to Ensure Proper Arrow Panel Visibility 13-6 Caution Mode Configuration for Arrow Panels 13-8 Changeable Message Signs 13-10 Sign Legibility 13-12 Determining Work Zone Speed Limits 14-1 Chapter 14 Rail-Highway Grade Crossings 14-2 Task Analysis of Rail-Highway Grade Crossings 14-4 Driver Information Needs at Passive Rail-Highway Grade Crossings 14-6 Timing of Active Traffic Control Devices at Rail-Highway Grade Crossings 14-8 Four-Quadrant Gate Timing at Rail-Highway Grade Crossings 14-10 Countermeasures to Reduce Gate-Rushing at Crossings with Two-Quadrant Gates 14-12 Human Factors Considerations in Traffic Control Device Selection at Rail-Highway Grade Crossings 15-1 Chapter 15 Special Considerations for Urban Environments 15-2 Methods to Increase Driver Yielding at Uncontrolled Crosswalks 15-4 Methods to Increase Compliance at Uncontrolled Crosswalks 15-6 Methods to Reduce Driver Speeds in School Zones 15-8 Signage and Markings for High Occupancy Vehicle (HOV) Lanes 15-10 Sight Distance Considerations for Urban Bus Stop Locations 16-1 Chapter 16 Special Considerations for Rural Environments 16-2 Passing Lanes 16-4 Countermeasures for Pavement/Shoulder Drop-offs 16-6 Rumble Strips 16-8 Design Consistency in Rural Driving 17-1 Chapter 17 Speed Perception, Speed Choice, and Speed Control 17-2 Behavioral Framework for Speeding 17-4 Speed Perception and Driving Speed 17-6 Effects of Roadway Factors on Speed 17-8 Effects of Posted Speed Limits on Speed Decisions 17-10 Speeding Countermeasures: Setting Appropriate Speed Limits 17-12 Speeding Countermeasures: Communicating Appropriate Speed Limits 17-14 Speeding Countermeasures: Using Roadway Design and Traffic Control Elements to Address Speeding Problems P A R T I V Human Factors Guidance for Traffic Engineering Elements 18-1 Chapter 18 Signing 18-2 General Principles for Sign Legends 18-4 Sign Design to Improve Legibility

18-6 Conspicuity of Diamond Warning Signs under Nighttime Conditions 18-8 Driver Comprehension of Signs 18-10 Complexity of Sign Information 19-1 Chapter 19 Changeable Message Signs 19-2 When to Use Changeable Message Signs 19-4 Presentation to Maximize Visibility and Legibility 19-6 Determining Appropriate Message Length 19-8 Composing a Message to Maximize Comprehension 19-10 Displaying Messages with Dynamic Characteristics 19-12 Changeable Message Signs for Speed Reduction 19-14 Presentation of Bilingual Information 20-1 Chapter 20 Markings 20-2 Visibility of Lane Markings 20-4 Effectiveness of Symbolic Markings 20-6 Markings for Pedestrian and Bicyclist Safety 20-8 Post-Mounted Delineators 20-10 Markings for Roundabouts 21-1 Chapter 21 Lighting 21-2 Countermeasures for Mitigating Headlamp Glare 21-4 Nighttime Driving 21-6 Daytime Lighting Requirements for Tunnel Entrance Lighting 21-8 Countermeasures for Improving Pedestrian Conspicuity at Crosswalks 21-10 Characteristics of Lighting that Enhance Pedestrian Visibility 21-12 Characteristics of Effective Lighting at Intersections P A R T V Additional Information 22-1 Chapter 22 Tutorials 22-2 Tutorial 1: Real-World Driver Behavior Versus Design Models 22-9 Tutorial 2: Diagnosing Sight Distance Problems and Other Design Deficiencies 22-35 Tutorial 3: Detailed Task Analysis of Curve Driving 22-38 Tutorial 4: Determining Appropriate Clearance Intervals 22-39 Tutorial 5: Determining Appropriate Sign Placement and Letter Height Requirements 22-43 Tutorial 6: Calculating Appropriate CMS Message Length under Varying Conditions 23-1 Chapter 23 References 24-1 Chapter 24 Glossary 25-1 Chapter 25 Index 26-1 Chapter 26 Abbreviations 27-1 Chapter 27 Equations

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TRB’s National Cooperative Highway Research Program (NCHRP) Report 600: Human Factors Guidelines for Road Systems: Second Edition provides data and insights of the extent to which road users’ needs, capabilities, and limitations are influenced by the effects of age, visual demands, cognition, and influence of expectancies.

NCHRP Report 600 provides guidance for roadway location elements and traffic engineering elements. The report also provides tutorials on special design topics, an index, and a glossary of technical terms.

The second edition of NCHRP 600 completes and updates the first edition, which was published previously in three collections.

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