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NCHRP Web-Only Document 316 Human Factors Guidelines for Road Systems 2021 UPDATE Volume 1: Updated and New Chapters James L. Brown David M. Prendez Joonbum Lee Alicia Romo Battelle Seattle, WA John L. Campbell Exponent Seattle, WA Jessica Hutton Ingrid Potts Darren Torbic MRI Global Kansas City, MO Updated and New Chapters for NCHRP Project 17-80 Submitted February 2020 NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed, and implementable research is the most effective way to solve many problems facing state departments of transportation (DOTs) administrators and engineers. Often, highway problems are of local or regional interest and can best be studied by state DOTs individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation results in increasingly complex problems of wide interest 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 initiated 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 (FHWA), United States Department of Transportation, under Agreement No. 693JJ31950003. 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, FTA, GHSA, NHTSA, 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. DISCLAIMER The opinions and conclusions expressed or implied in this report 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; the FHWA; or the program sponsors. The information contained in this document was taken directly from the submission of the author(s). This material has not been edited by TRB.
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. John L. Anderson 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.nationalacademies.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 provide leadership in transportation improvements and innovation through trusted, timely, impartial, and evidence-based information exchange, research, and advice regarding all modes of transportation. The Boardâs varied activities annually engage about 8,000 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.
CÂ OÂ OÂ PÂ EÂ RÂ AÂ TÂ IÂ VÂ EÂ RÂ EÂ SÂ EÂ AÂ RÂ CÂ HÂ PÂ RÂ OÂ GÂ RÂ AÂ MÂ SÂ Â Â Â CRP STAFF FOR NCHRP WEB-ONLY DOCUMENT 316, Volume 1 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Associate Program Manager, National Cooperative Highway Research Program David Jared, Senior Program Officer Clara Schmetter, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Kathleen Mion, Senior Editorial Assistant NCHRP PROJECT 17-80 PANEL Field of TrafficâArea of Safety John C. Milton, Washington State Department of Transportation, Olympia, WA (Chair) Susan Theresa Chrysler, Texas A&M Transportation Institute, College Station, TX Sean P. Coyle, Peoria, IL Peter R. Haag, Delaware Department of Transportation, Smyrna, DE James Allan Robertson, Lee Engineering, LLC, San Antonio, TX Rebecca Szymkowski, Wisconsin Department of Transportation, Madison, WI Samuel C. Tignor, Virginia Polytechnic Institute and State University (Virginia Tech), McLean, VA Jaime Tuddao, Nevada Department of Transportation, Carson City, NV Rosemarie Anderson, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Bernardo B. Kleiner, TRB Liaison
IV CONTENTS Introduction ......................................................................................................................................1 Organization of This Document in Relation to the HFG Second Edition ...............................1 Part I Updated Chapters Chapter 1 Why Have Human Factors Guidelines for Road Systems? ................................ 1-1 Chapter 5 Sight Distance ..................................................................................................... 5-1 Key Components of Sight Distance ........................................................................... 5-2 Determining Stopping Sight Distance ....................................................................... 5-4 Determining Intersection Sight Distance ................................................................... 5-6 Determining When to Use Decision Sight Distance .................................................. 5-8 Determining Passing Sight Distance ........................................................................ 5-10 Influence of Speed On Sight Distance ..................................................................... 5-12 Key References for Sight Distance Information ...................................................... 5-14 Where to Find Sight Distance Information for Specific Roadway Features ........... 5-16 Where to Find Sight Distance Information for Intersections ................................... 5-18 Chapter 10 Non-Signalized Intersections .......................................................................... 10-1 Acceptable Gap Distance ......................................................................................... 10-2 Factors Affecting Acceptable Gap ........................................................................... 10-4 Left-Turn Lanes at Non-Signalized Intersections .................................................... 10-6 Sight Distance at Left-Skewed Intersections ........................................................... 10-8 Sight Distance at Right-Skewed Intersections ....................................................... 10-10 Chapter 22 Tutorials .......................................................................................................... 22-1 Tutorial 1: Real-World Driver Behavior Versus Design Models...â¦.â¦â¦â¦.â¦â¦22-2 Tutorial 2: Diagnosing Sight Distance Problems and Other Design Deficiencies...22-9 Tutorial 3: Detailed Task Analysis of Curve Drivingâ¦â¦â¦â¦â¦.â¦â¦â¦â¦.â¦...22-35 Tutorial 4: Determining Appropriate Clearance Intervalsâ¦â¦â¦â¦â¦â¦â¦â¦.â¦.22-38 Tutorial 5: Determining Appropriate Sign Placement and Letter Height Requirementsâ¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦....22-39 Tutorial 6: Calculating Appropriate CMS Message Length under Varying Conditionsâ¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦â¦.22-43 Tutorial 7: Joint Use of the Highway Safety Manual (HSM) and the Human Factors Guidelines for Road Systems (HFG) ............................................................... 22-49
V Tutorial 8: Using the HFG to Support a Road Safety Audit (RSA) ...................... 22-71 Tutorial 9: Summary of HFG Topics ..................................................................... 22-75 Part II New Chapters Chapter 28 Pedestrians ...................................................................................................... 28-1 Task Analysis of Pedestrian Crossing In a Multiple Threat Scenario ..................... 28-2 Countermeasures to Reduce Pedestrian Exposure to Vehicles at Crossings ........... 28-4 Speed-Calming Countermeasures at Crosswalks ..................................................... 28-6 Improving Pedestrian Visibility and Conspicuity at Crosswalks ............................ 28-8 Selecting Beacons to Improve Pedestrian Conspicuity at Crosswalks .................. 28-10 Influence of the Built Environment on Pedestrian Crossing Safety ...................... 28-12 Design Challenges for Older Pedestrians .............................................................. 28-14 Pedestrian Rail Crossing Safety ............................................................................. 28-16 Key References for Pedestrian Crossing Safety Countermeasures ........................ 28-18 Chapter 29 Bicyclists ......................................................................................................... 29-1 Signals and Signal Timing for Bicycles at Intersections ......................................... 29-2 Markings for Bicycles at Intersections .................................................................... 29-4 Bicycle Lanes ........................................................................................................... 29-6 Separated Bicycle Lanes .......................................................................................... 29-8 Contraflow Bicycle Lanes...................................................................................... 29-10 Shared Use Lanes ................................................................................................... 29-12 Shared Bus-Bicycle Lanes ..................................................................................... 29-14 Mitigating Heavy Vehicle Conflicts with Bicycles ............................................... 29-16 Chapter 30 Roundabouts ................................................................................................... 30-1 Reducing Vehicle Speeds Approaching Roundabouts ............................................ 30-2 Increasing Driver Yielding Rates for Pedestrians at Roundabouts .......................... 30-4 Guide Signing at Roundabouts ................................................................................ 30-6 Accommodations for Bicyclists at Roundabouts ..................................................... 30-8 Countermeasures for Improving Accessibility for Visually Impaired Pedestrians at Roundabouts .................................................................................................... 30-10 Roundabout Lighting ............................................................................................. 30-12 Chapter 31 Additional References ............................................................................................. 31-1