U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590

Skip to content

Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

This report is an archived publication and may contain dated technical, contact, and link information
Publication Number: FHWA-RD-03-065
Date: September 2004

In-Vehicle Display Icons and Other Information Elements: Volume I

PDF Version (8.33 MB)

PDF files can be viewed with the Acrobat® Reader®



These guidelines are intended for use by anyone responsible for the conceptualization, development, design, testing, or evaluation of in-vehicle display icons and other information elements. During future project activities, these guidelines will be revised and expanded.

Chapters 2 through 7 contain the preliminary design guidelines produced through this effort. Chapter 2 provides general guidelines for icon design, and focuses on issues associated with the development of icons, when to use icons, and icon comprehension. Chapter 3 provides design guidelines for icon legibility, and focuses on issues associated with contrast, luminance, and the use of color. Chapter 4 provides design guidelines for icon recognition, and focuses on issues associated with the level of detail, the level of realism, and principles of perception to follow for the design of effective icons. Chapter 5 provides guidelines for icon interpretation, and focuses on the use of icons to convey system status and the effect of actions, and on identifying icons as part of a group. Chapter 6 provides guidelines for presenting auditory in-vehicle information, and focuses on the design of simple tones, earcons, auditory icons, and speech messages. Chapter 7 provides guidelines for the evaluation of in-vehicle icons, and focuses on the tests recommended by the International Organization for Standardization (ISO) (i.e., production test, appropriateness ranking test, comprehension/recognition test, and matching test). Chapter 8 includes a collection of icons for many messages. A tutorial describing in detail the process necessary for converting rank orders to scale values when evaluating icons using the appropriateness ranking test is provided in chapter 9. A design tool, useful for determining the sensory mode for presenting in-vehicle information, is provided in chapter 10.

This handbook can be used by individual designers in any number of ways. For example, it can be read, from start to finish, if one desires an overview of human factors issues, principles, data sources, and guidelines associated with the design of in-vehicle display icons. Alternatively, individual chapters can be reviewed by designers who would like to focus on specific topics, such as icon evaluation. 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 designer will dictate how and when it should be used.


In this handbook, a two-page format is used to present each design guideline. On each page, the main issue (e.g., Icon Legibility, Icon Recognition) being 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 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 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 below in figure 1-1; a detailed description of the presentation format of the guidelines follows.

figure 1 - Format Used in the Preliminary Design Guidelines. Click here for more detail.

Figure 1-1. Format Used in the Preliminary Design Guidelines


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


This subsection briefly defines the 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 gray box that is centered on the page.

In some cases, the design guideline is presented qualitatively in general terms (e.g., "text labels should be brief"). However, in most cases, the design guideline is presented quantitatively (e.g., "text labels should be no more than 2-3 words").

The Rating System

For some design parameters, enough empirical data exist to provide well-supported design guidelines, and the use of expert judgment is minimal. For others, empirical data have 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, little or no empirical data were available, and the design guideline was based primarily on expert judgment.

To aid in-vehicle display designers in making design trade-offs, individual design guidelines have been rated according to the relative contribution of empirical data and expert judgment to the design guideline. Specifically, each design guideline has been rated along a continuum and falling somewhere between "Based Primarily on Expert Judgment" and "Based Primarily on Experimental Data."

  • Based Primarily on Expert Judgment. Little or no empirical data were used to develop this design guideline. Expert judgment and design convention were used to develop this design guideline.

  • Based Equally on Expert Judgment and Experimental Data. Equal amounts of expert judgment and experimental data were used to develop this design guideline. Research findings may have lacked consistency, requiring greater amounts of expert judgment. Or, research may have been lacking in this specific area, requiring the results of research from related content domains to be interpreted for use in this context.

  • Based Primarily on Experimental Data. 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.

Figure, Table, or Graphic

A figure, table, or graphic augments the design guideline and provides "at-a-glance" information considered to be particularly important to the conceptualization and use of the design guideline. It provides 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 schematic examples of particular icons or symbols.



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

The discussion is presented primarily to help designers understand and explain or justify the design guideline to other members of the 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 design guidelines. In particular, the discussion 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 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.

Design Issues

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 design guidelines, special difficulties associated with the guideline's conceptualization or measurement, or special human performance implications associated with the design guideline.

Cross References

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


This subsection lists the references associated with the formulation of the 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, discussion, or design issues sections), and assigned a reference number. A complete reference section is provided in chapter 14 of this document.


A glossary is provided in chapter 12. Technical words and phrases are defined in the glossary and listed in the index (chapter 16). Abbreviations are provided in the glossary. Also, equations are numbered sequentially and listed separately in chapter 11 of this document.

Additional reference materials are also included. A summary of relevant U.S. Department of Transportation (USDOT), Society of Automotive Engineers (SAE), and ISO documents is provided in chapter 15.

Previous | Table of Contents | Next

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101