Comprehensive Human Factors Guidelines for Road Systems (Web-Only Document) (2005)

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4.0 Proposed Outline of the HFG The outline that follows proposes a structure and content for the HFG. It also offers a tentative title: Human Factors Guidelines for Road Systems: Design and Operational Considerations for the Road User. The phrase following the colon was introduced to address potential misunderstandings of the term “human factors” by possible users who have little familiarity with the field. As noted in Section 3.4, the outline that follows differs from the revised outline in the project Task 4 report (Lerner et al., 2002b) in two respects. First, the title of Chapter 5 has been revised to reflect the working title of the sample chapter (Appendix C). Second, an additional chapter, “Speed Perception, Speed Choice, and Speed Control,” has been added to the outline. It is inserted as “Chapter X.” Section 3.4 discussed the rationale for this new chapter. As noted there, this additional chapter has not been given a specific chapter number in order to maintain the chapter numbering from the Task 4 report. It would probably fit best between the numbered chapters 5 and 6. The proposed structure organizes the HFG into twenty-one chapters grouped under four major Parts. Part I (Introduction to the HFG) provides background on the needs for a human factors guidelines document, the purposes of the HFG, and an explanation of how to use the document. Part II (Bringing Road User Capabilities into Highway Design and Traffic Engineering Practice) is based around the road user. This is in contrast to the subsequent sections, which are organized around roadway factors. Part II describes the user-centered approach of human factors in a roadway system context and helps the practitioner think about the roadway from a road user’s perspective. Basic driver capabilities that directly relate to engineering practice are presented. Parts III and IV present the actual guidelines within the HFG. Part III is organized around specific roadway location elements, such as signalized intersections and work zones. This structure is most compatible with the likely problem solving mode and conceptual model of practitioner users. The first chapter within Part III deals explicitly with the key design considerations of speed (design speed vs. operating speed), sight distance, perception-reaction time, and their interrelationship. Then the remaining 11 chapters in this Part address specific roadway locations. Within this structure, design elements such as horizontal alignment, vertical alignment, and cross section are treated within the most appropriate chapter (e.g., horizontal alignment in the “Curves” chapter), and unique location-specific considerations are treated within other chapters. Part IV deals with traffic engineering elements, including signs, variable message signs, markings, and lighting. Thus Parts IV deals with the general non-location-specific human factors principles of these traffic engineering elements while Part III concerns location-specific applications. Cross-referencing and linking among the chapters of the various sections is assumed and will be critical. The practitioner facing an issue may conceptualize it in various ways and search the HFG for various terms. The links and cross-references avoid redundancy and steer the user to the appropriate guidance. 19

It is believed that the proposed technical chapters encompass the major highway design and traffic engineering issues that have important human factors considerations. They provide a reasonable scope for an initial version of the HFG. Although additional topics may be added later, the range of topics proposed here will make the initial HFG a reasonably comprehensive document for assisting practitioners in defining and addressing likely concerns. 20

HUMAN FACTORS GUIDELINES FOR ROAD SYSTEMS: DESIGN AND OPERATIONAL CONSIDERATIONS FOR THE ROAD USER PART I: INTRODUCTION TO THE HFG This part of the HFG explains the need for the HFG and the purposes for which it is intended. It then describes how to use the document, including the relationship to other design guides and linkages to background literature reviews. CHAPTER 1: WHY HAVE HUMAN FACTORS GUIDELINES FOR ROAD SYSTEMS? 1.1 What is Human Factors? 1.2 Why are Human Factors Guidelines for Road Systems necessary? • User-based design in a system safety context • Limitations to design guides ƒ Limited empirical basis ƒ Issues unaddressed by guidance ƒ Minimum specifications vs. range of applications ƒ Substantive safety (crash experience) vs. nominal safety (conformance to standards or accepted practices), cost effectiveness • Absence of comprehensive treatment in guideline format for practitioners 1.3 Purposes of this document • Recognize and address human factors-related issues • Incorporate human-centered concerns into design and planning • Provide basic information and principles of human factors and road user behavior • Provide resource for justification in decision making • What this document is not (textbook, tutorial, replacement or alternative to primary design references) CHAPTER 2: HOW TO USE THIS DOCUMENT How to use this document • Organization and format • Search capabilities • Background literature review papers • Relation to other standards and guidelines documents • Related resources 21

PART II: BRINGING ROAD USER CAPABILITIES INTO HIGHWAY DESIGN AND TRAFFIC ENGINEERING PRACTICE This part of the HFG is based around the road user. It concerns the role of the road user as part of the highway system and presents an overview of the important characteristics and capabilities of drivers and pedestrians. The first portion (Chapter 3) describes how road user characteristics are dealt with in a human factors approach and assists the practitioner in “thinking like a road user.” It helps the practitioner see the roadway from the perspective of the road user, especially the unfamiliar road user or the road user with limited capabilities because of inexperience, degraded perceptual ability, medical conditions, and transient states (fatigue, confusion, distraction, impairment). The second portion (Chapter 4) deals specifically with human capabilities basic to driving. It introduces key concepts and quantitative data. Guidelines in subsequent sections will cross-reference or link to the appropriate driver attributes in this section. The presentation in this chapter should be aimed at information that will be useful for practitioners. It should avoid the superficial introduction of technical topics that are not directly usable at the level of presentation (e.g., contrast sensitivity) and should not provide detailed treatments of physiology, basic sensory phenomena, cognitive mechanisms, etc. The emphasis is on application, not psychological process. Important principles should be explicitly indicated. This focused section should not be treated as a human factors text; it can reference or link to more detailed presentations in major reference sources, where appropriate. CHAPTER 3: A SYSTEM APPROACH TO HIGHWAY SAFETY: THINKING LIKE A ROAD USER 3.1 The Road User as a Component of the Highway System • Components of the highway system (range of users, vehicle, roadway environment) • The need for a systems perspective • Road function as a guiding factor • Crashes as system failure versus driver error • Human factors inputs for context-sensitive design 3.2 The Human Factors Approach to User-Centered Design • Designing for human capabilities, behaviors, and errors • Human factors considerations and the selection of design speed ¾ The linkage of design speed, speed choice, and perception-reaction time ¾ The relationship of speed and information handling • Human factors sources and methods (information base, task analysis, research) • Models of the road user (limited treatment, with reference to other sources) 22

3.3 Limitations of Highway Design and Traffic Engineering Guidance for User-Related Issues in Roadway Systems • Empirical basis of guidance (lacking, dated, limited range of users) • Minimum criteria may not be adequate for a given situation • Real world conflicts and complexities • Examples of cases where it is difficult to adhere to minimum specifications (due to geometric requirements, terrain and environmental features, etc.) 3.4 Thinking Like a Road User • Why the practitioner and the road user see things differently ƒ System overview, site familiarity, understanding of objectives, comprehension of TCDs and operations, motivations, capabilities, compartmentalized views ƒ Key questions ¾ Where are you in the road environment? ¾ What is the function of the road? • Basic principles distinguishing practitioners and roadway users ƒ Driver expectations ¾ Road user: expectancy (recent and immediate experience, personal history), mental model of traffic situation, critical role of next few seconds ¾ Designer: complete and accurate overview, knowledge of upcoming events ƒ Prior knowledge and expertise affect the process ¾ Prior knowledge and expertise influence pattern recognition, hazard recognition, automaticity (attentional effects), search patterns ¾ Road user make lack driving expertise and prior knowledge: perception as an active constructive process that takes time and is prone to errors ƒ Motivations are different ¾ Practitioner: Performance (operations and safety) at the network and roadway level; adherence to standards, guidance, usual practice; reducing costs ¾ Road user: me first, delay and frustration, navigating, competing (non-driving) tasks ƒ Understanding of the roadway ¾ Road user: imperfect understanding of TCDs, less ability to read the road, inaccurate risk perception ¾ Practitioner: knows meaning and purpose of each element and device, “secret codes,” likely hazards ƒ Information provision versus information handling ¾ Practitioner: formal requirements and standard means of presenting information ¾ Road user: searching and processing takes time; information load, primacy, shedding; conspicuity; attention and distraction ƒ Capabilities vary ¾ Road user: includes novices, reduced visual or cognitive capabilities, motor capabilities (pedestrian walking speed), transient states (fatigue, alcohol, drugs, emotional), lost or confused, environmental degradation (dark, glare, rain, obscuring large vehicles) 23

¾ Practitioner: generally good capabilities and not dealing with transient problems • Summary: Keys to thinking like a road user (steps or table) CHAPTER 4: BASIC ROAD USER CAPABILITIES 4.1 Human Visual Capabilities • Including legibility, day & night vision, glare, visual search patterns, range of abilities and anomalies, accommodation 4.2 Attention and Distraction • Including attention sharing among multiple sources, multi-task nature of driving task, external and in-vehicle sources of distraction 4.3 Information Handling • Including information processing time, visual scanning, information load, shedding of information 4.4 Expectancy • Including short term events and long term experience as determinants of expectancy, how expectancies are built, how they influence performance 4.5 Perception-Reaction Time • Including components of the perception-response process, factors that influence speed of perception and reaction, quantitative PRT functions 4.6 Speed Perception and Speed Choice • Including perception of own speed, errors in perception of others’ speeds and closing rates, determinants of speed choice 4.7 Hazard Perception and Risk Taking • Including road user abilities to detect various sorts of hazards, speed and reliability of hazard detection, anticipation of risks, judgment of risk, individual risk taking and risk management 4.8 Driver Age and Experience • Including older and novice road users, range of abilities, effects of age and inexperience on performance, countermeasures 4.9 Driver Impairments • Including prevalence and effects of fatigue, medication, alcohol, drugs 24

PART III: HUMAN FACTORS GUIDANCE FOR ROADWAY LOCATION ELEMENTS Parts III and IV of the HFG present the actual guidelines. Users may be most likely to enter the HFG at the level of Part III, searching for a solution to specific safety or operational concerns they are encountering. The organization of the chapters is based around major categories of roadway locations. The exception is for the initial chapter of this Part, which meets the need to emphasize the central themes of speed and time: principles of design vs. operating speed, sight distance, perception-reaction time, and their interrelationship. The location-specific guidance and discussion of this section will cross-reference the more general guidance regarding traffic engineering elements in Part IV. Combinations of geometries is a critical aspect and key cases must be treated within each chapter. CHAPTER 5: FROM DRIVER REACTION TIME, MANEUVER TIME, AND SPEED TO DESIGN DISTANCES: GENERAL GUIDELINES CHAPTER 6: CURVES (HORIZONTAL ALIGNMENT) 6.1 Background [see Chapter 5 of this report for description] 6.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 6.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 7: GRADES (VERTICAL ALIGNMENT) 7.1 Background [see Chapter 5 of this report for description] 7.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 7.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 8: TANGENT SECTIONS AND ROADSIDE (CROSS SECTION) 8.1 Background [see Chapter 5 of this report for description] 8.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 8.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 9: TRANSITION ZONES BETWEEN VARYING ROAD DESIGNS 9.1 Background [see Chapter 5 of this report for description] 9.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 9.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 10: NON-SIGNALIZED INTERSECTIONS 10.1 Background [see Chapter 5 of this report for description] 10.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 25

10.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 11: SIGNALIZED INTERSECTIONS 11.1 Background [see Chapter 5 of this report for description] 11.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 11.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 12: INTERCHANGES 12.1 Background [see Chapter 5 of this report for description] 12.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 12.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 13: CONSTRUCTION AND WORK ZONES 13.1 Background [see Chapter 5 of this report for description] 13.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 13.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 14: RAIL-HIGHWAY GRADE CROSSINGS 14.1 Background [see Chapter 5 of this report for description] 14.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 14.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 15: SPECIAL CONSIDERATIONS FOR URBAN ENVIRONMENTS 15.1 Background [see Chapter 5 of this report for description] 15.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 15.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 16: SPECIAL CONSIDERATIONS FOR RURAL ENVIRONMENTS 16.1 Background [see Chapter 5 of this report for description] 16.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 16.3 Guidelines [see Chapter 6 of this report for description] CHAPTER X: SPEED PERCEPTION, SPEED CHOICE, AND SPEED CONTROL 26

PART IV: HUMAN FACTORS GUIDANCE FOR TRAFFIC ENGINEERING ELEMENTS This section provides guidance for major cross-cutting issues for traffic engineering elements that are not specific to particular highway locations. The traffic engineering elements include signs, variable message signs, markings, and lighting. General principles and guidelines will be provided here. Application-specific recommendations will be under the appropriate chapters of Part III. CHAPTER 17: SIGNING 17.1 Background [see Chapter 5 of this report for description] 17.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 17.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 18: CHANGEABLE MESSAGE SIGNS 18.1 Background [see Chapter 5 of this report for description] 18.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 18.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 19: MARKINGS 19.1 Background [see Chapter 5 of this report for description] 19.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 19.3 Guidelines [see Chapter 6 of this report for description] CHAPTER 20: LIGHTING 20.1 Background [see Chapter 5 of this report for description] 20.2 Road User Requirements Analysis [see Chapter 5 of this report for description] 20.3 Guidelines [see Chapter 6 of this report for description] 27