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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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Suggested Citation:"Front Matter." National Academies of Sciences, Engineering, and Medicine. 2014. Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk. Washington, DC: The National Academies Press. doi: 10.17226/22297.
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TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2015 www.TRB.org The Second S T R A T E G I C H I G H W A Y R E S E A R C H P R O G R A M REPORT S2-S08A-RW-1 Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk TrenT VicTor, Marco Dozza, Jonas BärgMan, chrisTian-nils BoDa, Johan engsTröM, carol Flannagan, John D. lee, anD gusTaV Markkula SAFER Vehicle and Traffic Safety Centre Chalmers University of Technology Gothenburg, Sweden

Subject Areas Data and Information Technology Highways Operations and Traffic Management Safety and Human Factors Vehicles and Equipment

The Second Strategic Highway Research Program America’s highway system is critical to meeting the mobility and economic needs of local communities, regions, and the nation. Developments in research and technology—such as advanced materials, communications technology, new data collection tech- nologies, and human factors science—offer a new opportunity to improve the safety and reliability of this important national resource. Breakthrough resolution of significant transportation problems, however, requires concentrated resources over a short time frame. Reflecting this need, the second Strategic Highway Research Program (SHRP 2) has an intense, large-scale focus, integrates multiple fields of research and technology, and is fundamentally different from the broad, mission-oriented, discipline-based research programs that have been the mainstay of the highway research industry for half a century. The need for SHRP 2 was identified in TRB Special Report 260: Strategic Highway Research: Saving Lives, Reducing Congestion, Improving Quality of Life, published in 2001 and based on a study sponsored by Congress through the Transportation Equity Act for the 21st Century (TEA-21). SHRP 2, modeled after the first Strategic Highway Research Program, is a focused, time- constrained, management-driven program designed to com- plement existing highway research programs. SHRP 2 focuses on applied research in four areas: Safety, to prevent or reduce the severity of highway crashes by understanding driver behavior; Renewal, to address the aging infrastructure through rapid design and construction methods that cause minimal disruptions and produce lasting facilities; Reliability, to reduce congestion through incident reduction, management, response, and mitigation; and Capacity, to integrate mobility, economic, environmental, and community needs in the planning and designing of new trans- portation capacity. SHRP 2 was authorized in August 2005 as part of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU). The program is managed by the Transportation Research Board (TRB) on behalf of the National Research Council (NRC). SHRP 2 is conducted under a memo- randum of understanding among the American Association of State Highway and Transportation Officials (AASHTO), the Federal Highway Administration (FHWA), and the National Academy of Sciences, parent organization of TRB and NRC. The program provides for competitive, merit-based selection of research contractors; independent research project oversight; and dissemination of research results. SHRP 2 Reports Available by subscription and through the TRB online bookstore: www.mytrb.org/store Contact the TRB Business Office: 202-334-3213 More information about SHRP 2: www.TRB.org/SHRP2 SHRP 2 Report S2-S08A-RW-1 ISBN: 978-0-309-27423-4 © 2015 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 copy- right to any previously published or copyrighted material used herein. The second Strategic Highway Research Program grants permission to repro- duce 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, or FHWA endorsement of a particular prod- uct, method, or practice. It is expected that those reproducing material in this document for educational and not-for-profit purposes will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from SHRP 2. Note: SHRP 2 report numbers convey the program, focus area, project number, and publication format. Report numbers ending in “w” are published as web documents only. Notice The project that is the subject of this report was a part of the second Strategic 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 committee selected to monitor this project and review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical committee 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 second Strategic 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 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 achieve- ments of engineers. Dr. C. D. (Dan) Mote, Jr., 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. Victor J. Dzau 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. C. D. (Dan) Mote, Jr., 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 Transportation Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisci- plinary, 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 Transporta- tion, and other organizations and individuals interested in the development of transportation. www.TRB.org www.national-academies.org

ACKNOWLEDGMENTS This work was sponsored by the Federal Highway Administration in cooperation with the American Asso- ciation of State Highway and Transportation Officials. It was conducted in the second Strategic Highway Research Program (SHRP 2), which is administered by the Transportation Research Board of the National Academies. This project was managed by Kenneth L. Campbell, Chief Program Officer for SHRP 2 Safety, and James Hedlund, SHRP 2 Special Consultant for Safety Coordination. The research reported on herein was performed by SAFER Vehicle and Traffic Safety Centre at Chalmers, Gothenburg, Sweden. SAFER is a joint research center of excellence in vehicle and traffic safety composed of 25 partners from the Swedish automotive industry, academia, and other organizations (www.chalmers. se/safer). SAFER’s host and legal entity is Chalmers University of Technology. Principal investigator Trent Victor is an adjunct professor at Chalmers and worked on the project as borrowed personnel to Chalmers, but his main employer is Volvo Cars. The other authors of this report are co-principal investigator Marco Dozza, Jonas Bärgman, and Christian-Nils Boda of Chalmers University of Technology (as a SAFER part- ner); Johan Engström and Gustav Markkula of Volvo Group Trucks Technology (as a SAFER partner); John D. Lee of the University of Wisconsin–Madison (as a consultant to SAFER); and Carol Flannagan of University of Michigan Transportation Research Institute (as a consultant to SAFER). The authors acknowledge the contributions to this research from Ines Heinig, Vera Lisovskaja, Olle Nerman, Holger Rootzén, Dmitrii Zholud, Helena Gellerman, Leyla Vujic´, Martin Rensfeldt, Stefan Venbrant, Akhil Krishnan, Bharat Mohan Redrouthu, and Daniel Nilsson of Chalmers; Mikael Ljung-Aust of Volvo Cars; Erwin Boer; and Christer Ahlström and Omar Bagdadi of VTI. SHRP 2 STAFF Ann M. Brach, Director Stephen J. Andrle, Deputy Director Cynthia Allen, Editor Kenneth Campbell, Chief Program Officer, Safety Jared Cazel, Editorial Assistant JoAnn Coleman, Senior Program Assistant, Capacity and Reliability Eduardo Cusicanqui, Financial Officer Richard Deering, Special Consultant, Safety Data Phase 1 Planning Shantia Douglas, Senior Financial Assistant Charles Fay, Senior Program Officer, Safety Carol Ford, Senior Program Assistant, Renewal and Safety James Hedlund, Special Consultant, Safety Coordination Alyssa Hernandez, Reports Coordinator Ralph Hessian, Special Consultant, Capacity and Reliability Andy Horosko, Special Consultant, Safety Field Data Collection William Hyman, Senior Program Officer, Reliability Linda Mason, Communications Officer David Plazak, Senior Program Officer, Capacity and Reliability Rachel Taylor, Senior Editorial Assistant Dean Trackman, Managing Editor Connie Woldu, Administrative Coordinator

The SHRP 2 Naturalistic Driving Study (NDS) was the largest and most comprehensive study of its kind ever undertaken. Its central goal was to produce unparalleled data from which to study the role of driver performance and behavior in traffic safety and how driver behavior affects the risk of crashes. Such research involves understanding how a driver inter- acts with and adapts to the vehicle, the traffic environment, roadway characteristics, traffic control devices, and other environmental features. After-the-fact crash investigations can only provide this information indirectly. The NDS data recorded how drivers really drove and what they were doing just before they crashed or almost crashed. The Roadway Information Database (RID), created in parallel with the NDS, contains detailed roadway data collected on more than 12,500 centerline miles of highways in and around the six study sites, about 200,000 highway miles of data from the highway inventories of the six study states, and additional data on crash histories, traffic and weather conditions, work zones, and ongoing safety campaigns in the study sites. The NDS and RID data can be linked to associate driving behavior with the roadway environment. The data will be used for years to come for developing and evaluating safety countermeasures designed to prevent or reduce the severity of traffic crashes and injuries. The NDS collected data from more than 3,000 male and female volunteer passenger-vehicle drivers, aged 16 to 98, during a 3-year period. Most drivers participated from 1 to 2 years. It was conducted at one site in each of six states: Florida, Indiana, New York, North Caro- lina, Pennsylvania, and Washington. Data collected included vehicle speed, acceleration, and braking; vehicle controls, when available; lane position; forward radar; and video views forward, to the rear, and on the driver’s face and hands. The NDS data file contains about 50 million vehicle miles, 5 million trips, more than 3,900 vehicle years, and more than 1 mil- lion hours of video—a total of about 2 petabytes of data. Four contracts were awarded in 2012 under SHRP 2 Safety Project S08, Analysis of the SHRP 2 Naturalistic Driving Study Data, to study specific research questions using the early NDS and RID data. An open competition solicited proposals to address topics of the con- tractor’s own choosing that would have direct safety applications and that would • Lead to real-world applications and safety benefits (theoretical knowledge without poten- tial applications was not a priority); • Be broadly applicable to a substantial number of drivers, roadways, or vehicles in the United States; and • Demonstrate the use of the unique NDS data (i.e., similar results could not be obtained from existing nonnaturalistic data sets). In addition to these goals, SHRP 2 expected the projects to serve as both pilot testers and advisers. As they conducted these first substantial NDS and RID analyses, these stud- ies’ experienced researchers would discover valuable insights on a host of both pitfalls and opportunities that others should know about when they use the data. F O R EWO R D James Hedlund, SHRP 2 Special Consultant, Safety Coordination

The four projects began in February 2012 and were conducted in two phases. In Phase 1, which concluded in December 2012, contractors obtained an initial set of data, tested and refined their research plans, and developed detailed plans for their full analyses. Three projects successfully completed this proof of concept and were selected for Phase 2. These three projects obtained and analyzed a much richer, though still preliminary, data set and reported their results in July 2014. This report, Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk, documents one of the three projects. These projects were conducted while the NDS and RID data files were being built. This circumstance imposed constraints that substantially affected the researchers’ work. The con- straints included the following: • Sample size. In summer 2013, when the projects requested full data sets, the NDS data file was only 20% to 30% complete. As a result, each project could only obtain a fraction of the trips of interest now available in the full NDS data. • RID not complete and not linked to the NDS. Projects based on roads of specific types or locations could not identify these roads from the RID but instead had to use Google Earth or a similar database to identify them. They then obtained trips of interest by using searches through the NDS that were less efficient than will be possible when the NDS and RID are linked. • Data processing. Some data, such as radar, had not been processed from their raw state to a form where they were fully ready for analysis. • Data quality. NDS data are field data, and field data are inherently somewhat messy. At the time these projects obtained their data, some data had not been quality controlled, and some characteristics of the data were not yet well understood. • Tools for data users. Not all crashes and near crashes had been identified, and a separate small data set containing only crashes, near crashes, and baseline exposure segments had not been built. In addition, a small trip summary file containing key features of each trip had not been built. Users can conduct initial analyses on many subjects quickly and easily using a trip summary file. • Other demands on data file managers. The first priority for the NDS manager, Virginia Tech Transportation Institute (VTTI), and the RID manager, Iowa State University’s Cen- ter for Transportation Research and Education (CTRE), was to complete data processing and quality control. Field data were being ingested continually. Data delivery for users was sometimes delayed because of these demands on their resources. These issues are being resolved in 2014. The NDS and RID data are complete and are being linked. Data processing and quality control are being completed. Crash and near-crash files and trip summary files are being built. If this project and the other two were to begin in 2015, each would have more data and would obtain the data far more easily and quickly. Readers should keep these constraints in mind as they read this report. Despite working under these constraints, the three NDS projects have produced valuable new insights into important traffic safety issues that will help reduce traffic crashes and injuries. For an overview of the study, see the following article: K. L. Campbell, The SHRP 2 Natu- ralistic Driving Study: Addressing Driver Performance and Behavior in Traffic Safety, TR News, No. 282, September–October 2012, pp. 30–35. Additional details may be found at the study’s InSight website: https://insight.shrp2nds.us/.

C O N T E N T S 1 Executive Summary 1 Background 4 Key Results 9 Discussion and Conclusions 12 CHAPTER 1 Background 13 1.1 Summary of Project Aims 14 1.2 SHRP 2 Naturalistic Driving Study Background 16 CHAPTER 2 Data Set Formation and General Methodology 16 2.1 SHRP 2 Naturalistic Driving Study Data 16 2.2 Formal Data Access Procedures 16 2.3 Targeted General Crash Population 16 2.4 Event Sample-Size Request 18 2.5 Event Sampling 20 2.6 Final Sample Size 20 2.7 Export Format 20 2.8 Event Data 21 2.9 Time-Series and Video Data 30 CHAPTER 3 Differences Between Event Types in Descriptive Variables 30 3.1 Overview of Differences 31 3.2 Differences in Descriptive Variables 41 CHAPTER 4 Risk from Distracting Activity Types 41 4.1 Methods 42 4.2 Distracting Activities 43 4.3 Driver Impairments 45 4.4 Conclusions 46 CHAPTER 5 Risk at the Precipitating Event 46 5.1 Risk from Total Eyes off Path Time at the Precipitating Event 48 5.2 Eyes-off-Path Risk in Time Segments at the Precipitating Event 49 5.3 Conclusions 51 CHAPTER 6 Risk from Eyes off Path Before Crash or Minimum Time to Collision 51 6.1 Distribution of Glances Over Time 56 6.2 Eyes-off-Path Risk in Time Segments Preceding Crash or Minimum Time to Collision 59 6.3 Risk from Glance Sequences Preceding Crash or Minimum Time to Collision 62 6.4 Risk Contributions from Distracting Activities Over and Above What Can Be Explained by Glance Behavior 64 6.5 Conclusions

65 CHAPTER 7 Timing of Eyes off Path Relative to Situation Kinematics and Visual Cues 66 7.1 Method 66 7.2 Results 68 7.3 Timing of the Last Glance Relative to Situation Kinematics 71 7.4 Mismatch Mechanisms: Last Glance Duration Versus invTTC Change Rate 76 7.5 What Triggers Drivers’ Responses After the Last Glance? 84 7.6 Conclusions 87 CHAPTER 8 Actual and Potential Severity 88 8.1 The Three Potential Severity Scales 88 8.2 What-If Simulation Basics and the Calculation of MIR and MCR 90 8.3 Actual Outcome Severity Versus Potential Outcome Severity 91 8.4 Glance Duration Analysis 92 8.5 Secondary-Task Analysis 95 8.6 Generalization Analysis: Comparison of DeltaV Metrics 96 8.7 Generalization Analysis: Extreme Value Analysis 98 8.8 General Discussion on Actual and Potential Severity 100 8.9 Conclusions on Actual and Potential Severity 102 CHAPTER 9 Conclusions and Recommendations 111 Glossary 113 References 117 Appendix A. Actual and Potential Outcome Severity Scales

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TRB’s second Strategic Highway Research Program (SHRP 2) Report S2-S08A-RW-1: Analysis of Naturalistic Driving Study Data: Safer Glances, Driver Inattention, and Crash Risk explores the relationship between driver inattention and crash risk in lead-vehicle precrash scenarios (corresponding to rear-end crashes).

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