Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
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 875 Guidance for Evaluating the Safety Impacts of Intersection Sight Distance Kimberly Eccles Scott Himes Kara Peach Frank Gross Richard J. Porter VHB Raleigh, NC Timothy J. Gates MicHigan State UniVerSity East Lansing, MI Christopher M. Monsere Portland State UniVerSity Portland, OR Subscriber Categories Highways â¢ Design â¢ Safety and Human Factors 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 875 Project 17-59 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-44681-5 Library of Congress Control Number 2018934192 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.
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 ACKNOWLEDGMENTS The research reported here was performed under NCHRP Project 17-59 by VHB, Wayne State Univer- sity, and Portland State University. VHB was the prime contractor for this study. Ms. Kimberly Eccles, P.E., Safety Practice Leader at VHB, was the Project Director and Principal Inves- tigator. The other authors of this report were Dr. Scott Himes, P.E., Highway Safety Engineer at VHB; Ms. Kara Peach, Transportation Planner at VHB; Dr. Frank Gross, P.E., Highway Safety Engineer at VHB; Dr. Timothy Gates, P.E., PTOE, Associate Professor at Michigan State University (formerly of Wayne State University); and Dr. Christopher M. Monsere, P.E., Associate Professor at Portland State University. Dr. Richard Porter, P.E., Highway Safety Engineer at VHB, provided direction on specifying the statistical road safety models for crash modification factor development. CRP STAFF FOR NCHRP RESEARCH REPORT 875 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Stephan A. Parker, Senior Program Officer Cheryl Keith, Senior Program Assistant Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Doug English, Editor NCHRP PROJECT 17-59 PANEL Field of TrafficâArea of Safety J. Michael Y. Ereti, Gunda Corporation, LLC, Houston, TX (Chair) In-Kyu âQâ Lim, Virginia DOT, Richmond, VA Michelle Lynn Neuner, Missouri DOT, Freeburg, MO Stacey Lynn Pierce, Wisconsin DOT, Waukesha, WI Bonnie S. Polin, Massachusetts Department of Transportation, Boston, MA Norman H. Roush, Consultant, Racine, OH R. Scott Zeller, Washington State DOT, Olympia, WA Wei Zhang, FHWA Liaison Kelly K. Hardy, AASHTO Liaison Stephen F. Maher, TRB Liaison
NCHRP Research Report 875: Guidance for Evaluating the Safety Impacts of Intersection Sight Distance is a resource for practitioners involved in the planning, design, operations, and traffic safety management of stop-controlled intersections. It provides information on how to estimate the effect of intersection sight distance (ISD) on crash frequency at inter sections and describes data collection methods and analysis steps for making safety- informed decisions about ISD. The guidance also provides basic information on the impor- tance of ISD that can be shared with decision makers and other stakeholders. Accompanying the report, NCHRP Web-Only Document 228: Safety Impacts of Inter- section Sight Distance documents the methodology and presents the results from the under- lying research on estimating the safety effects of ISD at stop-controlled intersections. To establish the relationship between ISD and safety at stop-controlled intersections, crash, traffic, and geometric data were collected for 832 intersection approaches with minor- road stop control in North Carolina, Ohio, and Washington. The provision of appropriate ISD is an important element in intersection design. The approach to the determination of ISD in AASHTOâs A Policy on Geometric Design of High- ways and Streets (known as the âGreen Bookâ) is based on gap-acceptance developed in the 1996 NCHRP Report 383: Intersection Sight Distance. That approach includes the ability to more easily calculate ISD for both passenger cars and trucks by allowing the selection of an ISD âdesign vehicle.â Calculations of ISD using that approach yield different results from those calculated with earlier methods. However, past research efforts to analyze and quantify the safety impacts of ISD have produced inconsistent results, making it difficult to fully evaluate the different approaches. The quantification of safety impacts allows better design evaluations that include variations in available ISD. It also provides the opportunity to evaluate the potential safety impacts of the ISD criteria in the Green Book. Under NCHRP Project 17-59, a team led by VHB was asked to (1) identify appropriate definitions and methods to measure ISD, (2) quantify the relationship between safety and available ISD (i.e., crash modification factors and other appropriate functions), and (3) develop guidance for transportation agencies on how to apply these functions to evaluate the safety impacts of available sight distance. The project team undertook a phased approach to gather information to develop the guidance. First, they reviewed existing ISD practices and relationships. Next, they developed a study design for quantifying the relationships of ISD and safety, along with a data collection plan. The team used the approved research plan to conduct a critical review of the current practices in uncontrolled intersection methodol- ogy, to collect field data, and to assemble and model the data collected. Models were refined through additional data collection and in testing the draft guidance with key stakeholders. F O R E W O R D By Stephan A. Parker Staff Officer Transportation Research Board
The team received comments from the NCHRP Project 17-59 panel on key deliverables in each stage of the guidelinesâ development. These comments were integral to shaping the structure and content of the guidance. The guidance and methodology report (NCHRP Web-Only Document 228 and a Power- Point presentation describing the entire project) are available at www.TRB.org by searching for âNCHRP Research Report 875.â
1 Summary 3 Chapter 1 Introduction 3 Purpose of the Guidance 4 Scope of This Guidance 4 How to Use This Guidance 5 Definitions and Acronyms 8 Chapter 2 Measuring Sight Distance and Other Critical Information 9 Data Collection Approach 10 Traffic Volumes 10 Crash History 14 Chapter 3 Safety Performance and Intersection Sight Distance 14 Determining the CMF 22 Analyzing More Than One Approach 24 Chapter 4 Examples 24 Example 1: One Direction ISD Upgrade 24 Example 2: Upgrading Both Left and Right Departure Sight Triangles from Different Values 28 Example 3: Calculation of Total Crashes CMF 29 Example 4: Design Deviation Using Equations 32 Chapter 5 Other Considerations and Resources 32 Countermeasures 33 Resources 34 Chapter 6 Base Equations for Reference 34 CMFunctions 35 Unknown AADT 36 References C O N T E N T S