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Human Factors Design Guidelines for Advanced Traveler Information Systems (ATIS)and Commercial Vehicle Operations (CVO)

CHAPTER 1: HOW TO USE THESE DESIGN GUIDELINES

INTRODUCTION

THE TWO–PAGE FORMAT

THE LEFT–HAND PAGE

THE RIGHT–HAND PAGE

OTHER FEATURES

INTRODUCTION

These guidelines are intended to be used by anyone responsible for the conceptualization, development, design, testing, or evaluation of Advanced Traveler Information Systems (ATIS) and Commercial Vehicle Operations (CVO) devices.

Chapter 2 provides an overview of ATIS and CVO and summarizes the subsystems and functions of ATIS/CVO devices. Chapters 3 through 9 contain the design guidelines produced through this effort. Chapter 3 provides general design guidelines for ATIS/CVO displays, and focuses on issues associated with symbol legibility, use of color, and display content for ATIS/CVO. Chapter 4 provides general design guidelines for ATIS/CVO controls, and focuses on the selection of control types, control design, and population stereotypes for control movement. Chapters 5 through 8 provide, respectively, the design guidelines for Routing and Navigation, Motorist Services, Safety/Warning, and Augmented Signage Information. While chapters 3 through 8 will be of value to all designers of ATIS/CVO devices, chapter 9 provides guidelines specific to CVO systems and functions. A set of Design Tools, useful for determining the sensory mode and trip status associated with individual ATIS/CVO messages, is provided in chapter 10.

This handbook can be used by individual designers in any number of ways. For example, it can be read through, from start to finish, if one desires an overview of human factors issues, principles, data sources, and guidelines associated with ATIS/CVO devices. Also, individual chapters can be reviewed by designers who would like to focus on specific ATIS functions, such as routing and navigation. Finally, designers may simply refer to specific guidelines, equations, terms, and references as their individual needs warrant. Thus, there is no "right" way to use this handbook––the day–to–day needs of the individual ATIS/CVO designer dictate how and when it should be used.

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THE TWO–PAGE FORMAT

In this handbook, a two–page format is used to present each design guideline. On each page, the ATIS/CVO function (e.g., Routing and Navigation, Safety/Warning, etc.) addressed by the guideline is indicated by centered, bold type within the header. As described in more detail below, the left–hand page presents the title of the guideline, an introduction and overview of the design guideline, the design guideline itself, the 4–star rating associated with the guideline, and a graphic, table, or figure that augments the text information. The right–hand page provides the more detailed supporting rationale for the design guideline that a designer may need in order to perform his or her day–to–day design tasks, as well as special design considerations, a space for designer notes, and a list of key references. A sample guideline, with key features highlighted, is shown in the following figure.

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THE LEFT–HAND PAGE

The guideline title is indicated by centered, bold type at the top of the left–hand page.

Introduction

This subsection briefly defines the ATIS/CVO design guideline and provides basic information about the design parameter and the guideline. For example, this subsection might be used to provide the unit of measurement (e.g., visual angle, meters, footlamberts, etc.) for the guideline, or to provide equations for the derivation of certain parameters.

Design Guideline

This subsection presents a quantitative design guideline (when possible), either as a point value, a range, or an explicit recommendation. The design guideline is always presented prominently and is enclosed in a yellow/blue box that is centered on the page.

In some cases, the design guideline is presented qualitatively in general terms; e.g., "Higher reliability levels may be required by drivers in a familiar setting than in an unfamiliar setting." However, in most cases, the design guideline is presented quantitatively; e.g., "Traffic information should be at least 70 percent reliable."

Importantly, the guidelines do not present requirements for ATIS/CVO devices, either for system content or design. However, if an ATIS/CVO device includes a function covered by these guidelines, then this handbook presents a summary of human factors design practice.

The 4–Star Rating System

For some ATIS/CVO design parameters, there is enough empirical data to provide well–supported design guidelines, and the use of expert judgment is minimal. For others, empirical data has only provided the foundation for a decision about what the design guideline should be, but experience and judgment have been used to determine the final design guideline. For yet other topics, there was little or no empirical data available and the design guideline was based primarily on expert judgment.

To aid ATIS designers in making design trade–offs, individual design guidelines have been assigned a rating, using a "star rating" system, that corresponds to the relative contribution that empirical data and expert judgment have each made to the design guideline. Specifically, each design guideline has been assigned either 1, 2, 3, or 4 stars, using the following criteria:

	Based on high quality and consistent data sources that apply directly to the guideline. Empirical data from highly relevant content domains (e.g., transportation human factors, navigation system design) were primarily used to develop this design guideline. Little expert judgment was required to develop this design guideline.
	Based on high quality and generally applicable data sources with at least some consistency across the sources. Empirical data from related content domains (e.g., nuclear power, military systems) were primarily used to develop this design guideline. Expert judgment was used, mostly as support, to develop this design guideline.
	Based on limited empirical data; research findings may not all agree. Expert judgment was primarily used to develop this design guideline, although the empirical sources were used as secondary sources.
	Based primarily on expert judgment or design convention. Little or no empirical data were used to develop this design guideline.

Users of this handbook should be cautious as they interpret the 4–star ratings. Again, the ratings only refer to the relative contribution of expert judgment versus empirical data to the development of the guideline. Although the ratings are correlated with the quality or validity of the guidelines, users should not infer that a guideline with four stars is "better" or more valid than a guideline with one star––it simply has more empirical support. Furthermore, the relative importance of any particular guideline depends on the design situation and the designer's solution to trade–offs among system goals.

Figure, Table, or Graphic

This subsection provides a figure, table, or graphic to augment the design guideline. This figure, table, or graphic provides "at–a–glance" information considered to be particularly important to the conceptualization and use of the design guideline. It serves to provide a visual representation of the design guideline (or some aspect of the design guideline) that may be difficult to grasp from the design guideline itself, which is quantitative and text–based.

This figure, table, or graphic might take many forms, including: a drawing depicting a generic application of a design guideline or a particular design issue, a flowchart of measurement procedures for the design guideline, a table that summarizes the design guideline, or graphics such as icons or in–vehicle signs.

Many of the figures in this handbook present digital maps depicting actual highways, landmarks, and city streets. Such figures are used in order to increase the usability and relevance of the guidelines and to illustrate general design principles. They are schematic examples for their associated guideline. Unless it is indicated otherwise, they are not intended to convey specific recommendations on the color, design, or format of ATIS displays.

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THE RIGHT–HAND PAGE

Supporting Rationale

This subsection briefly summarizes the rationale behind the choice of the design guideline. In particular, the Supporting Rationale explains the logic, premises, assumptions, and the train–of–thought associated with the development of the design guideline. The Supporting Rationale can take many forms, including a brief review of applicable empirical studies, references to traditional design practice, or an analysis of relevant information.

The Supporting Rationale is presented primarily to help ATIS designers understand the design guideline and to help them explain or justify the design guideline to other members of the ATIS development team. Also, since these human factors design guidelines are expected to be revised as additional empirical data become available, this subsection will be useful to future developers of ATIS/CVO design guidelines. In particular, the Supporting Rationale will enable future design guideline developers to determine how new human factors information can (or should) be integrated into the existing design guidelines.

For example, the design guideline for daytime symbol contrast has been developed through consideration of expected "worst case" ambient luminance, anticipated driver populations, and contrast requirements under representative laboratory conditions. If new data for the "worst case" ambient luminance are obtained (or if new assumptions are made), future design guideline developers will be able to assess the role and relative importance of ambient luminance associated with the current design guideline for daytime symbol contrast and determine what (if any) changes should be made to the design guideline.

Special Design Considerations

This subsection presents special design considerations associated with a particular design guideline. These special considerations might include design goals from the perspective of other disciplines (e.g., optics, packaging, displays), interactions with other ATIS/CVO design guidelines, cross references to other design guidelines, special difficulties associated with the guideline's conceptualization or measurement, or special human performance implications associated with the design guideline. This discussion is organized around specific issues considered important to the design of the ATIS.

Cross References

This subsection lists the titles and page numbers of other guidelines within the handbook that are relevant to the current guideline.

Notes

Where space is available, this subsection provides a convenient space for handbook users to record special notes, ideas, questions, etc., associated with a particular design guideline.

Key References

This subsection lists the key references associated with the formulation of the ATIS/CVO design guideline. Each of these references will already have been noted within the text of the design guideline (e.g., as part of the discussion included in the Introduction, Supporting Rationale, or Special Design Considerations), and assigned a reference number. A complete reference section is provided in chapter 14 of this document.

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OTHER FEATURES

Within the text of the design guidelines, technical words and phrases are defined in the Glossary (chapter 12) and listed in the Index (chapter 20). Also, equations are numbered sequentially and listed separately in chapter 11 of this document.

Additional reference materials are also included. A General Human Factors Bibliography is provided in chapter 15. Publications that have been produced during this effort (i.e., project reports, journal articles, book chapters, and conference papers) are provided in chapter 16. Finally, relevant U.S. Department of Transportation (DOT) and Society of Automotive Engineers (SAE) documents are listed in chapter 17.

The Scope and Limitations for these guidelines are discussed in chapter 18. A brief description of the methods used to produce these guidelines is provided in chapter 19.

FHWA-RD-98-057