Acceleration, Deceleration, and Stopping Sight Distance Criteria for Geometric Design of Highways and Streets (2024)

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2024 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 1081 Acceleration, Deceleration, and Stopping Sight Distance Criteria for Geometric Design of Highways and Streets Peter Savolainen Timothy Gates Megat Usamah Megat Johari Anshu Bamney Hisham Jashami Nischal Gupta Akinfolarin Abatan Michigan State University East Lansing, MI Eric Donnell S. Ilgin Guler Agnimitra Sengupta The Pennsylvania State University University Park, PA Edward Smaglik Northern Arizona University Flagstaff, AZ Je Gooch VHB Raleigh, NC Shauna Hallmark Streetwise Transportation Consultants, LLC Ankeny, IA Subscriber Categories Design • Highways Research sponsored by the American Association of State Highway and Transportation Ofcials in cooperation with the Federal Highway Administration

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 transporta- tion results in increasingly complex problems of wide interest to high- way 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 (FHWA), United States Department of Transportation, under Agree- ment No. 693JJ31950003. 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 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 iden- tified by chief administrators and other staff of the highway and transportation departments, by committees of AASHTO, and by the FHWA. Topics of the highest merit are selected by the AASHTO Special Committee on Research and Innovation (R&I), and each year R&I’s 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 https://www.mytrb.org/MyTRB/Store/default.aspx Printed in the United States of America NCHRP RESEARCH REPORT 1081 Project 15-75 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-70932-3 Library of Congress Control Number 2023952226 © 2024 by the National Academy of Sciences. National Academies of Sciences, Engineering, and Medicine and the graphical logo are trade- marks of the 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, APTA, FAA, FHWA, FTA, GHSA, or NHTSA 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; the FHWA; or the program sponsors. The Transportation Research Board does not develop, issue, or publish standards or spec- ifications. The Transportation Research Board manages applied research projects which provide the scientific foundation that may be used by Transportation Research Board sponsors, industry associations, or other organizations as the basis for revised practices, procedures, or specifications. 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 or logos appear herein solely because they are considered essential to the object of the report.

e 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. e 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. e 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. e 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. e 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. e Transportation Research Board is one of seven major program divisions of the National Academies of Sciences, Engineering, and Medicine. e mission of the Transportation Research Board is to mobilize expertise, experience, and knowledge to anticipate and solve complex transportation-related challenges. e Board’s varied activities annually engage about 8,500 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. e 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 15-75 by Michigan State University (MSU). Dr. Peter T. Savolainen, P.E., MSU Foundation Professor and Interim Chair of Civil and Envi- ronmental Engineering at MSU, was the Project Director and Principal Investigator. The other authors of this report are Dr. Timothy J. Gates, Professor of Civil Engineering at MSU and Co-Principal Investigator; Dr. Eric Donnell, Professor of Civil Engineering at the Pennsylvania State University (PSU); Dr. S. Ilgin Guler, Associate Professor of Civil Engineering at PSU; Dr. Edward Smaglik, Professor of Civil Engineering at Northern Arizona University; Jeff Gooch of VHB; Dr. Shauna Hallmark of Streetwise Transportation Consultants, LLC; Dr. Megat Usamah Megat Johari, Dr. Anshu Bamney, and Dr. Hisham Jashami, Research Associates at MSU; Nischal Gupta and Akinfolarin Abatan, Research Assistants and PhD students at MSU; and Agnimitra Sengupta, Research Assistant and PhD student at PSU. CRP STAFF FOR NCHRP RESEARCH REPORT 1081 Waseem Dekelbab, Deputy Director, Cooperative Research Programs, and Manager, National Cooperative Highway Research Program Amir N. Hanna, Senior Program Officer Emily Griswold, Senior Program Assistant Natalie Barnes, Director of Publications Heather DiAngelis, Associate Director of Publications Hilary Freer, Senior Editor NCHRP PROJECT 15-75 PANEL Field of Design—Area of General Design Jeff C. Jones, Tennessee Department of Transportation, Nashville, TN (retired) (Chair) Ahmed F. Al-Kaisy, Montana State University, Bozeman, MT Jeffrey D. Bucher, Pennsylvania Department of Transportation, Harrisburg, PA Michael S. Fleming, Washington State Department of Transportation, Olympia, WA David R. McDonald, Jr., Hanson Professional Services, Inc., Lisle, IL Richard D. Wilder, New York State Department of Transportation, Albany, NY Jeffrey B. Shaw, FHWA Liaison

NCHRP Research Report 1081 presents (1) the results of a study that reviewed and evalu- ated available guidelines for acceleration, deceleration, and stopping sight distance criteria for geometric design of highways and streets and (2) proposed changes. Implementing these changes could result in reduced environmental impacts, savings in construction costs, and reductions in construction time. The information contained in this report will help highway agencies and other organizations address relevant issues when considering the planning of highways and streets. Acceleration, deceleration, and stopping sight distance (SSD) criteria are necessary con- siderations for determining geometric design requirements of roadways. Acceleration and deceleration are influenced by many factors, including grade, vehicle type, and maneuver type. Similarly, SSD is influenced by various factors, such as brake reaction time, object height, and driver-eye height. The 7th edition of A Policy on Geometric Design of Highways and Streets (also known as the 2018 Green Book) provides guidelines for determining these design criteria. However, because recent changes in the vehicle fleet, vehicle technologies, and the characteristics of driver population affect these criteria, research was needed to identify the limitations of current guidelines for acceleration, deceleration, and SSD criteria; develop improved guidelines; and propose changes to the current guidelines. Under NCHRP Project 15-75, “Update of the Policy on Geometric Design of Highways and Streets Guidelines for Acceleration/Deceleration and Stopping Sight Distance Cri- teria,” Michigan State University was tasked with proposing updates to the guidelines for acceleration/deceleration and SSD criteria contained in the 2018 Green Book. To accomplish this objective, the research team reviewed the guidelines for acceleration, deceleration, and SSD criteria contained in the 2018 Green Book and conducted a series of field studies that examined driver behavior at acceleration and deceleration lanes, as well as characteristics of the driver population and vehicle fleet as they relate to SSD policy. The results of these field studies were used to assess the adequacy of current design policy and related assump- tions about driver and vehicle characteristics and related performance measures. These field studies were supplemented by a series of crash data analyses to assess relationships between crash risk and design policies related to acceleration lanes, deceleration lanes, and SSD. The results of these studies were used to develop draft language for consideration by AASHTO to incorporate the research results in the next update of the Green Book. This report summarizes the work performed in the project. The contractor’s final report included appendices that elaborate on the work performed in the project; these appendices are available online at www.trb.org by searching for “NCHRP Project 15-75”. F O R E W O R D By Amir N. Hanna Staff Officer Transportation Research Board

1-1 Chapter 1 Introduction 1-1 1.1 Background 1-1 1.2 Objectives and Scope 1-2 1.3 Overview of Research Method 1-2 1.4 Outline of Report 2-1 Chapter 2 Background and Pertinent Literature 2-1 2.1 AASHTO SSD Model 2-4 2.2 Characteristics Influencing SSD and ASD 2-4 2.2.1 Driver and Vehicle Characteristics Influencing Minimum SSD 2-10 2.2.2 Driver and Object Characteristics Influencing ASD 2-12 2.3 AASHTO Speed-Change Lane Design 2-14 2.4 Factors Influencing Acceleration Lane Design 2-17 2.4.1 Speed of Vehicles when Entering the Acceleration Lane 2-17 2.4.2 Speed of Merging Vehicles at End of Acceleration Lane 2-17 2.4.3 Manner of Acceleration 2-18 2.5 Factors Influencing Deceleration Lane Design 2-20 2.5.1 Speed when Entering the Deceleration Lane 2-20 2.5.2 Speed at End of Deceleration Lane/Start of Controlling Geometric Feature 2-22 2.5.3 Manner of Deceleration 3-1 Chapter 3 Research Approach and Analysis 3-1 3.1 State Agency Survey 3-2 3.2 Analysis of Naturalistic Driving Data and Emerging Technologies 3-2 3.2.1 SHRP2 NDS Data Investigation 3-9 3.2.2 Insurance Institute for Highway Safety/Highway Loss Data Institute AEB Test Data Investigation 3-14 3.3 Evaluation of Characteristics of Vehicle Fleet 3-14 3.3.1 Data Collection 3-14 3.3.2 Data Summary 3-17 3.4 Field Studies of Vehicle Acceleration and Deceleration Performance 3-17 3.4.1 Methods 3-23 3.4.2 Results 3-26 3.5 Crash-Based Evaluations of SCLs and SSD 3-26 3.5.1 Evaluation of SSD-Related Crash Risks 3-38 3.5.2 Evaluation of SCL-Related Crash Risks 3-48 3.6 Probabilistic/Reliability-Based Design 3-48 3.6.1 Stopping Sight Distance 3-60 3.6.2 Crest Vertical Curves 3-64 3.6.3 Sag Vertical Curve at Undercrossing 3-67 3.6.4 Acceleration and Deceleration Lane Length Design C O N T E N T S

4-1 Chapter 4 Conclusions and Proposed Revisions 4-1 4.1 Summary of Findings and Conclusions 4-1 4.1.1 SSD 4-2 4.1.2 Acceleration Lane Length 4-4 4.1.3 Deceleration Lane Length 4-5 4.2 Proposed Revisions to the 2018 AASHTO Policy on Geometric Design of Highways and Streets (Green Book) 4-5 4.3 Suggested Research R-1 References A-1 Abbreviations 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 nap.nationalacademies.org) retains the color versions.