In-Vehicle Display Icons and

Other Information Elements

Volume I: Guidelines

PUBLICATION NO. FHWA-RD-03-065 SEPTEMBER 2004

Research, Development, and Technology

Turner-Fairbank Highway Research Center

6300 Georgetown Pike

McLean, VA 22101-2296
IN-VEHICLE DISPLAY ICONS AND 

OTHER INFORMATION ELEMENTS: 

VOLUME I: GUIDELINES 
FOREWORD 

This is one of a series of reports produced as part of a contract to develop precise and detailed 

human factors design guidelines for in-vehicle display icons and other information elements. 

The contractual effort consists of three phases: analytical, empirical, and integrative. 

This report is a product of the integrative phase. This handbook summarizes human engineering 

data, guidelines, and principles for use by designers during the development and evaluation of 

in-vehicle icons and other information elements. 

Copies of this report can be obtained through the Research and Technology Report Center, 9701 

Philadelphia Court, Unit Q, Lanham, MD 20706; telephone: 301–577–0818; fax: 301–577–1421; 

or the National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA 

22161; telephone: 703–487–4650; fax: 703–321–8547. 

Michael F. Trentecoste 

Director 

Office of Safety Research and Development 

NOTICE

This document is disseminated under the sponsorship of the U.S. Department of Transportation 

in the interest of information exchange. The U.S. Government assumes no liability for its 

contents or use thereof. This report does not constitute a standard, specification, or regulation. 

The U.S. Government does not endorse products or manufacturers. Trade and manufacturers’ 

names appear in this report only because they are considered essential to the objective of this 

document. 

QUALITY ASSURANCE STATEMENT 

The Federal Highway Administration (FHWA) provides high-quality information to serve 

Government, industry, and the public in a manner that promotes public understanding. Standards 

and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its 

information. FHWA periodically reviews quality issues and adjusts its programs and process to 

ensure continuous quality improvement. 
Technical Report Documentation Page

1. Report No. 

 FHWA-RD-03-065 

2. Government Accession No. 3. Recipient's Catalog No. 

5. Report Date 

September 2004 

4. Title and Subtitle 

In-Vehicle Display Icons and Other Information Elements 

Volume I: Guidelines 6. Performing Organization Code 

7. Author(s) 

Campbell, J. L., Richman, J. B., Carney, C., and Lee, J. D. 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

Battelle Human Factors Transportation Center 

4500 Sand Point Way NE 

Seattle, WA 98105-3949 

11. Contract or Grant No. 

DTFH61-97-C-00061 

13. Type of Report and Period Covered 

Integrative Report 8/15/99– 6/17/2002 

 

12. Sponsoring Agency Name and Address 

Office of Safety Research and Development 

Federal Highway Administration 

6300 Georgetown Pike 

McLean, VA 22101-2296 

14. Sponsoring Agency Code 

15. Supplementary Notes: Contracting Officer's Technical Representative (COTR) – Thomas M. Granda 

16. Abstract: 

Because of the speed with which, In-Vehicle Information System (IVIS) devices are entering the automotive marketplace, 

many research issues associated with the design of in-vehicle visual symbols and other information elements have not 

been adequately addressed. The overall goal of the “In-Vehicle Display Icons and Other Information Elements” project 

has been to provide the designers of these in-vehicle technologies with a set of design guidelines for in-vehicle display 

icons and other information elements. Specific objectives of this project were to: 

• Design and perform experimentation to select appropriate symbols for in-vehicle use; use the resulting data to write 

final guidelines for in-vehicle symbols usage, encompassing both current and future symbols. 

• Write preliminary, as well as empirically based, final guidelines. 

The key product of this project is a set of clear, concise, and user-centered human-factors design guidelines for in-vehicle 

icon design. The 42 guidelines address issues such as the legibility, recognition, interpretation, and evaluation of 

graphical and text-based icons and symbols. These guidelines provide IVIS developers with key information regarding 

the use and integration of existing and new visual symbols. In addition, guidelines are provided for the design of invehicle auditory information.

17. Key Words 

Human Factors, Driver Information, Design Guidelines, Icon Design, Visual 

Symbols, Icon Interpretation, Icon Legibility, Auditory Messages, General 

vs. Specific Icons, Icon Recognition, Icon Evaluation 

18. Distribution Statement 

No restrictions. This document is 

available to the public through the 

National Technical Information Service, 

Springfield, VA 22161. 

19. Security Classif. (of this report) 

None 

20. Security Classif. (of this page) 

None 

21. No. of Pages 

238 

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
SI* (MODERN METRIC) CONVERSION FACTORS 

APPROXIMATE CONVERSIONS TO SI UNITS

Symbol When You Know Multiply By To Find Symbol 

LENGTH

in inches 25.4 millimeters mm

ft feet 0.305 meters m

yd yards 0.914 meters m 

mi miles 1.61 kilometers km

AREA

in2 square inches 645.2 square millimeters mm2

ft2 square feet 0.093 square meters m2

yd2 square yard 0.836 square meters m2

ac acres 0.405 hectares ha 

mi2 square miles 2.59 square kilometers km2

VOLUME

fl oz fluid ounces 29.57 milliliters mL

gal gallons 3.785 liters L

ft3 cubic feet 0.028 cubic meters m3 

yd3 cubic yards 0.765 cubic meters m3 

NOTE: volumes greater than 1000 L shall be shown in m3

MASS oz ounces 28.35 grams g

lb pounds 0.454 kilograms kg

T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") 

TEMPERATURE (exact degrees) o

F Fahrenheit 5 (F-32)/9 Celsius oC 

or (F-32)/1.8

ILLUMINATION

fc foot-candles 10.76 lux lx

fl foot-Lamberts 3.426 candela/m2 cd/m2

FORCE and PRESSURE or STRESS

lbf poundforce 4.45 newtons N 

lbf/in2 poundforce per square inch 6.89 kilopascals kPa

APPROXIMATE CONVERSIONS FROM SI UNITS 

Symbol When You Know Multiply By To Find Symbol

LENGTH mm millimeters 0.039 inches in

m meters 3.28 feet ft

m meters 1.09 yards yd 

km kilometers 0.621 miles mi

AREA mm2 square millimeters 0.0016 square inches in2 

m2 square meters 10.764 square feet ft

2 

m2 square meters 1.195 square yards yd2 

ha hectares 2.47 acres ac

km2 square kilometers 0.386 square miles mi2 

VOLUME mL milliliters 0.034 fluid ounces fl oz 

L liters 0.264 gallons gal

m3 cubic meters 35.314 cubic feet ft3 

m3 cubic meters 1.307 cubic yards yd3 

MASS 

g grams 0.035 ounces oz

kg kilograms 2.202 pounds lb

Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T

TEMPERATURE (exact degrees) o

C Celsius 1.8C+32 Fahrenheit oF 

ILLUMINATION

lx lux 0.0929 foot-candles fc 

cd/m2 candela/m2 0.2919 foot-Lamberts fl

FORCE and PRESSURE or STRESS

N newtons 0.225 poundforce lbf 

kPa kilopascals 0.145 poundforce per square inch lbf/in2

*SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. 

(Revised March 2003)

ii 
iii 

TABLE OF CONTENTS 

CHAPTER 1: HOW TO USE THESE DESIGN GUIDELINES ......................................... 1-1 

Introduction.................................................................................................................................. 1-1 

The Two-Page Format ................................................................................................................. 1-1 

The Left-Hand Page..................................................................................................................... 1-2 

Introduction...................................................................................................................... 1-2 

Design Guideline ............................................................................................................. 1-3 

The Rating System........................................................................................................... 1-3

Figure, Table, or Graphic................................................................................................. 1-4 

The Right-Hand Page................................................................................................................... 1-4 

Discussion........................................................................................................................ 1-4 

Design Issues ................................................................................................................... 1-4 

Cross References.............................................................................................................. 1-5 

References........................................................................................................................ 1-5 

Other Features.............................................................................................................................. 1-5 

CHAPTER 2: GENERAL ISSUES IN ICON DESIGN........................................................ 2-1 

General Development Process for In-Vehicle Icons.................................................................... 2-2 

When to Use Icons....................................................................................................................... 2-4 

Ways to Use Icons ....................................................................................................................... 2-6 

Types of Visual Icons .................................................................................................................. 2-8 

Composition of an Icon.............................................................................................................. 2-10 

Sequence of Icon Comprehension ............................................................................................. 2-12

CHAPTER 3: ICON LEGIBILITY ........................................................................................ 3-1 

Determining the Appropriate Luminance Uniformity within an Icon......................................... 3-2 

Determining the Appropriate Contrast within an Icon ................................................................ 3-4 

Determining the Appropriate Size of Icon Components ............................................................. 3-6 

Designing Effective Text Labels ................................................................................................. 3-8 

The Effects of Color on Icon Legibility..................................................................................... 3-10 

CHAPTER 4: ICON RECOGNITION................................................................................... 4-1 

Level of Realism.......................................................................................................................... 4-2 

Level of Detail ............................................................................................................................. 4-4 

Perceptual Principles of Icon Design........................................................................................... 4-6 

Flash Rate .................................................................................................................................... 4-8 

Design of Prohibition Symbols.................................................................................................. 4-10 

Driver Acceptance of General versus Specific Icons ................................................................ 4-12 
iv 

CHAPTER 5: ICON INTERPRETATION............................................................................ 5-1 

Enhancing Icon Interpretation with Text Labels ......................................................................... 5-2 

Composition of Text Labels......................................................................................................... 5-4 

Conveying the Effect of Actions with Icons................................................................................ 5-6 

Identifying Icons as Part of a Group............................................................................................ 5-8 

Conveying System Status with Icons......................................................................................... 5-10

Enhancing Icon Interpretation with Color ................................................................................. 5-12 

Conveying Urgency with Icons ................................................................................................. 5-14 

Enhancing Icon Interpretation with Shape................................................................................. 5-16 

CHAPTER 6: THE AUDITORY PRESENTATION OF IN-VEHICLE 

INFORMATION........................................................................................................................ 6-1 

Augmenting Icons with Auditory Information ............................................................................ 6-2 

Determining the Appropriate Auditory Signal ............................................................................ 6-4 

Design of Simple Tones............................................................................................................... 6-6 

Design of Complex Tones ........................................................................................................... 6-8 

Design of Earcons...................................................................................................................... 6-10 

Design of Auditory Icons........................................................................................................... 6-12 

Design of Speech Messages....................................................................................................... 6-14 

Perceived Urgency of Auditory Signals .................................................................................... 6-16 

General Design Guidelines for Automatic Speech Recognition Systems ................................. 6-18 

Timing of Auditory Navigation Information ............................................................................. 6-20 

Perceived Annoyance of Auditory Signals................................................................................ 6-22 

CHAPTER 7: EVALUATING IN-VEHICLE ICONS.......................................................... 7-1 

Overview of General Procedures for Evaluating In-Vehicle Icons ............................................. 7-2 

Production Test ............................................................................................................................ 7-4 

Appropriateness Ranking Test..................................................................................................... 7-6 

Comprehension/Recognition Test................................................................................................ 7-8 

Matching Test ............................................................................................................................ 7-10 

Additional Symbol Evaluation Approaches .............................................................................. 7-12 

CHAPTER 8: ICON COLLECTION ..................................................................................... 8-1 

Augmented Signage..................................................................................................................... 8-3 

Automated/Adaptive Cruise Control Devices ............................................................................. 8-5 

Collision Avoidance Information ................................................................................................ 8-5 

Commercial Vehicle Operations (CVO) Information................................................................ 8-10 

General Navigation System Information ................................................................................... 8-12 

Motorist Services Information ................................................................................................... 8-12 

Routing and Navigation ............................................................................................................. 8-34 

Safety and Warning Information ............................................................................................... 8-40 
v 

CHAPTER 9: TUTORIALS .................................................................................................... 9-1 

Tutorial 1: Analysis of Rank Order Data..................................................................................... 9-1

Tutorial 2: Providing Subjects with Context During Icon Evaluations..................................... 9-11 

CHAPTER 10: SENSORY MODALITY DESIGN TOOL................................................. 10-1 

CHAPTER 11: LIST OF EQUATIONS............................................................................... 11-1 

CHAPTER 12: GLOSSARY.................................................................................................. 12-1 

CHAPTER 13: ACKNOWLEDGMENTS ........................................................................... 13-1 

CHAPTER 14: REFERENCES............................................................................................. 14-1 

CHAPTER 15: RELEVANT U.S. DEPARTMENT OF TRANSPORTATION, SOCIETY 

OF AUTOMOTIVE ENGINEERS, AND INTERNATIONAL ORGANIZATION FOR 

STANDARDIZATION DOCUMENTS ................................................................................. 15-1 

CHAPTER 16: INDEX........................................................................................................... 16-1 
vi 

LIST OF FIGURES

CHAPTER 1

Figure 1-1. Format Used in the Preliminary Design Guidelines .............................................. 1-2 

CHAPTER 2

Figure 2-1. General Development Process for In-Vehicle Icons.............................................. 2-2 

Figure 2-2. Examples of the Appropriate Use of Icons ............................................................ 2-4 

Figure 2-3. Information Processing Elements Used to Identify Icon Requirements ................ 2-6 

Figure 2-4. Types of Icons........................................................................................................ 2-8 

Figure 2-5. Key Components of an Icon................................................................................. 2-10 

Figure 2-6. Sequence of Icon Comprehension and Use.......................................................... 2-12 

CHAPTER 3

Figure 3-1. Measuring Luminance Nonuniformity................................................................... 3-2 

Figure 3-2. Example of Measuring Contrast ............................................................................ 3-4 

Figure 3-3. Relationship Between Viewing Distance, Symbol Height, and Visual Angle ...... 3-6 

Figure 3-4. Schematic Examples of Text Labels...................................................................... 3-8 

Figure 3-5. Equation for Determining Color Contrast............................................................ 3-10 

CHAPTER 4

Figure 4-1. Five Levels of Realism .......................................................................................... 4-2 

Figure 4-2. Example of Appropriate Level of Detail................................................................ 4-4 

Figure 4-3. Perpetual Principles of Icon Design....................................................................... 4-6 

Figure 4-4. Schematic Examples of the Appropriate and Inappropriate Use of Flashing 

 Icons ....................................................................................................................... 4-8 

Figure 4-5. Examples of Alternative Methods for Indicating Prohibition.............................. 4-10 

Figure 4-6. Examples of General and Specific Icons for Key In-Vehicle Message 

 Categories............................................................................................................. 4-12 

CHAPTER 5

Figure 5-1. Examples of Icons that Benefit from Text Labels ................................................. 5-2 

Figure 5-2. Schematic Examples of Conveying Action............................................................ 5-6 

Figure 5-3. Schematic Examples of Ways to Identify Icons as Part of a Group ...................... 5-8 

Figure 5-4. Examples of Conveying Status ............................................................................ 5-10 

Figure 5-5. Schematic Examples of the Use of Color in Icons............................................... 5-12 

Figure 5-6. Schematic Examples of Conveying Urgency....................................................... 5-14 

Figure 5-7. Locations of Icons Within the Visual Field (Adapted from Reference 2) ........... 5-15 

Figure 5-8. Schematic Examples of the Use of Shape in Icons.............................................. 5-16 
vii 

CHAPTER 6 

Figure 6-1. Temporal Parameters of Auditory Signals—Pulse, Burst, and Sound Parameters 

 Defined Graphically ............................................................................................... 6-8 

Figure 6-2. Brake Reaction Times for Different Warning Sounds (from Reference 2) ......... 6-12 

Figure 6-3. Example of Using Steven’s Power Law for Producing Urgency Exponents....... 6-16 

Figure 6-4. Equations for Determining the Appropriate Timing of an Instruction ................ 6-20 

Figure 6-5. Appropriateness Depends on Perceived Annoyance for Benign Situations 

(e.g., e-mail notification), Whereas Appropriateness Depends on Perceived 

Urgency for Highly Critical Situations (e.g., collision avoidance)...................... 6-22 

CHAPTER 7

Figure 7-1. Overview of Procedures for Evaluating In-Vehicle Icons..................................... 7-2 

Figure 7-2. Production Test ...................................................................................................... 7-4 

Figure 7-3. Appropriateness Ranking Test............................................................................... 7-6 

Figure 7-4. Comprehension/Recognition Test.......................................................................... 7-8 

Figure 7-5. Matching Test ...................................................................................................... 7-10 

CHAPTER 9

Figure 9-1. Sample Icon.......................................................................................................... 9-12 

Figure 9-2. Motorists Services Icon........................................................................................ 9-12 

CHAPTER 10

Figure 10-1. Sensory Modality Design Tool .......................................................................... 10-1 

Figure 10-2. Steps for Using the Sensory Modality Design Tool .......................................... 10-2 

Figure 10-3. Rules for Determining Display Modality........................................................... 10-3 
viii 

LIST OF TABLES

CHAPTER 3

Table 3-1. Determining the Appropriate Size of Icon Components ......................................... 3-6 

CHAPTER 5

Table 5-1. Examples of Text Label Composition..................................................................... 5-4 

CHAPTER 6 

Table 6-1. Heuristics for Assessing Priority............................................................................. 6-2 

Table 6-2. Heuristics for Assessing Complexity ...................................................................... 6-2 

Table 6-3. Ratings of Audio Signals for Various Functions..................................................... 6-4 

Table 6-4. Advantages and Disadvantages Associated with the Use of Simple Tones............ 6-6 

Table 6-5. Three Methods for Constructing Earcons (from Reference 3).............................. 6-10 

Table 6-6. Determining the Number of Information Units..................................................... 6-14 

Table 6-7. Examples of Auditory Messages........................................................................... 6-14 

Table 6-8. Issues to Consider When Designing ASR Systems............................................... 6-18 

Table 6-9. Sound Characteristics that Increase Urgency, While Having a Modest Effect 

on Annoyance ........................................................................................................ 6-22 

CHAPTER 7

Table 7-1. Summary of Additional Symbol Evaluation Approaches ..................................... 7-12 

CHAPTER 9

Table 9-1. Samples Data Set: Ranks Assigned to 5 Icons by 10 Judges .................................. 9-1 

Table 9-2. A Composite Ranking of Icons Obtained from Sums of Assigned Ranks.............. 9-2 

Table 9-3. Mean Rank of Each of the Icons ............................................................................. 9-2 

Table 9-4. Computations for the Choice Score Method ........................................................... 9-4 

Table 9-5. p–z Conversion Table.............................................................................................. 9-5 

Table 9-6. Matrix A .................................................................................................................. 9-6 

Table 9-7. Matrix B .................................................................................................................. 9-7 

Table 9-8. Matrix C .................................................................................................................. 9-7 

Table 9-9. Matrix D .................................................................................................................. 9-7 

Table 9-10. Matrix E................................................................................................................. 9-8 

Table 9-11. Matrix F................................................................................................................. 9-8 

Table 9-12. Matrix G ................................................................................................................ 9-8 

Table 9-13. Step 8: Assigning Interval-Scale Values.............................................................. 9-9 

Table 9-14. Summary of Methods Discussed for Analyzing Rank Order Data ..................... 9-10 
 

CHAPTER 1: HOW TO USE THESE DESIGN GUIDELINES 

INTRODUCTION

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. 

THE TWO-PAGE FORMAT

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 

 1-1
 

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. 

DETERMINING THE APPROPRIATE LUMINANCE UNIFORMITY WITHIN AN ICON

Introduction: Luminance uniformity refers to the consistency of luminance values across an icon. Moderate

DETERMINING THE APPROPRIATE LUMINANCE UNIFORMITY WITHIN AN ICON

Introduction:

nonuniformities in luminance may only lead to the perception, by the driver, that the display is of poor quality.

With great nonuniformities in luminance, however, drivers may not be provided with sufficient luminance and

Contrast to ensure adequate legibility in certain areas of the display.

Icon Design Guidelines ICON LEGIBILITY May 17, 1999 Icon Design Guidelines ICON LEGIBILITY May 17, 1999

3-3

Right-hand page

References

Cross

References

Design

Issues

Discussion

Abbreviated

Handbook Title

(Both Pages)

Abbreviated

Chapter Title

(Both Pages)

Revision Date

(Both Pages) Guideline Title Bar Scale Rating

Introduction

Design

Guideline

References:

1. Mueller, C. G. (1951). Frequency of seeing functions for intensity discrimination at various levels of

adapting intensity. Journal of General Psychology, 34, 463-474.

2. Boff, K. R., Kaufman, L., & Thomas, J. P. (1986). Handbook of perception and human performance. New

York: J. Wiley & Sons.

3. Farrell, R. J., & Booth, J. M. (1984). Design handbook for imagery interpretation equipment. Seattle,

WA: Boeing Aerospace Company.

4. American National Standards Institute. (1988). American national standard for human factors engineering

of visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society.

5. MIL-STD-1472D. (1989). Human engineering design criteria for military systems, equipment and

facilities. Washington, DC: U.S. Government Printing Office.

Discussion: Threshold Luminance Discrimination Data. Although observers in Reference 1 could discriminate

lights that differed in luminance by as little as 10 percent, these data were obtained when they were trying to

detect a luminance difference between a background and a target under ideal laboratory conditions (see 

Reference 2 also). Thus, 10 percent represents a threshold luminance discrimination value and is far too

conservative for IVIS use, in which the issue of concern is the driver's ability to notice luminance differences

under normal driving or normal viewing conditions.

Tolerance for Luminance Variations. Reference 3 indicates that luminance in cathode ray tubes (CRTs) typically

varies by as much as 37 percent and is either not noticed or is considered to be acceptable by observers. 

Reference 4 recommends that luminance variations remain below 50 percent. Reference 5 indicates that while

the preferred limit for luminance variation across optical projection displays is 33 percent, an unacceptable limit 

is 66 percent.

Conclusions. The design objectives provided above reflect a composite of the information provided by

References 3, 4, and 5. Specifically, if luminance differences up to 37 percent are not always noticed by

observers and if 33 percent represents a preferred limit, then 33 percent seems to be an acceptable limit for smallarea luminance nonuniformities (i.e., within an individual element or segment). Both 50 percent and 66 percent 

have been suggested as absolute upper limits on luminance nonuniformities.

Design Issues: Causes. Luminance nonuniformities are generally caused by the display itself. In vacuum

fluorescent displays (VFDs) being viewed directly, for example, these might be caused by poor phosphor

distribution on the inside of the anodes, or by fluctuations in the power supply output.

Cross References:

Determining the Appropriate Contrast within an Icon, p. 3-4

Measuring Luminance Uniformity

Luminance A Luminance B

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Uniformity = 

|(Luminance min

) - (Luminance max)|

(Luminance max)

(Eq. 1)

Where: Luminance min= the smaller luminance value

Luminance max= the greater luminance value

3-2

Left-hand page

Page Numbers

Figure,

Table, or

Graphic

Provide no more than 33% Element Uniformity (within an individual element or segment).

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Experimental Data

Based Primarily on

Expert Judgment

Design Guidelines

DETERMINING THE APPROPRIATE LUMINANCE UNIFORMITY WITHIN AN ICON

Introduction: Luminance uniformity refers to the consistency of luminance values across an icon. Moderate

DETERMINING THE APPROPRIATE LUMINANCE UNIFORMITY WITHIN AN ICON

Introduction:

nonuniformities in luminance may only lead to the perception, by the driver, that the display is of poor quality.

With great nonuniformities in luminance, however, drivers may not be provided with sufficient luminance and

Contrast to ensure adequate legibility in certain areas of the display.

Icon Design Guidelines ICON LEGIBILITY May 17, 1999 Icon Design Guidelines ICON LEGIBILITY May 17, 1999

3-3

Right-hand page

References

Cross

References

Design

Issues

Discussion

Abbreviated

Handbook Title

(Both Pages)

Abbreviated

Chapter Title

(Both Pages)

Revision Date

(Both Pages) Guideline Title Bar Scale Rating

Introduction

Design

Guideline

References:

1. Mueller, C. G. (1951). Frequency of seeing functions for intensity discrimination at various levels of

adapting intensity. Journal of General Psychology, 34, 463-474.

2. Boff, K. R., Kaufman, L., & Thomas, J. P. (1986). Handbook of perception and human performance. New

York: J. Wiley & Sons.

3. Farrell, R. J., & Booth, J. M. (1984). Design handbook for imagery interpretation equipment. Seattle,

WA: Boeing Aerospace Company.

4. American National Standards Institute. (1988). American national standard for human factors engineering

of visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society.

5. MIL-STD-1472D. (1989). Human engineering design criteria for military systems, equipment and

facilities. Washington, DC: U.S. Government Printing Office.

Discussion: Threshold Luminance Discrimination Data. Although observers in Reference 1 could discriminate

lights that differed in luminance by as little as 10 percent, these data were obtained when they were trying to

detect a luminance difference between a background and a target under ideal laboratory conditions (see 

Reference 2 also). Thus, 10 percent represents a threshold luminance discrimination value and is far too

conservative for IVIS use, in which the issue of concern is the driver's ability to notice luminance differences

under normal driving or normal viewing conditions.

Tolerance for Luminance Variations. Reference 3 indicates that luminance in cathode ray tubes (CRTs) typically

varies by as much as 37 percent and is either not noticed or is considered to be acceptable by observers. 

Reference 4 recommends that luminance variations remain below 50 percent. Reference 5 indicates that while

the preferred limit for luminance variation across optical projection displays is 33 percent, an unacceptable limit 

is 66 percent.

Conclusions. The design objectives provided above reflect a composite of the information provided by

References 3, 4, and 5. Specifically, if luminance differences up to 37 percent are not always noticed by

observers and if 33 percent represents a preferred limit, then 33 percent seems to be an acceptable limit for smallarea luminance nonuniformities (i.e., within an individual element or segment). Both 50 percent and 66 percent 

have been suggested as absolute upper limits on luminance nonuniformities.

Design Issues: Causes. Luminance nonuniformities are generally caused by the display itself. In vacuum

fluorescent displays (VFDs) being viewed directly, for example, these might be caused by poor phosphor

distribution on the inside of the anodes, or by fluctuations in the power supply output.

Cross References:

Determining the Appropriate Contrast within an Icon, p. 3-4

Measuring Luminance Uniformity

Luminance A Luminance B

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Uniformity = 

|(Luminance min

) - (Luminance max)|

(Luminance max)

(Eq. 1)

Where: Luminance min= the smaller luminance value

Luminance max= the greater luminance value

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Uniformity = 

|(Luminance min

) - (Luminance max)|

(Luminance max)

(Eq. 1) % Element

Uniformity = 

|(Luminance min

) - (Luminance max)|

(Luminance max)

|(Luminance min

) - (Luminance max)|

(Luminance max)

(Eq. 1)

Where: Luminance min= the smaller luminance value

Luminance max= the greater luminance value

3-2

Left-hand page

Page Numbers

Figure,

Table, or

Graphic

Provide no more than 33% Element Uniformity (within an individual element or segment).

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Experimental Data

Based Primarily on

Expert Judgment

Design Guidelines

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

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 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. 

 1-2
 

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. 

 1-3
 

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. 

THE RIGHT-HAND PAGE 

Discussion

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. 

 1-4
 

Cross References

This subsection lists the titles and page numbers of other guidelines within the handbook that are 

relevant to the current guideline. 

References

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. 

OTHER FEATURES

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. 

 1-5
 

CHAPTER 2: GENERAL ISSUES IN ICON DESIGN 

General Development Process for In-Vehicle Icons..................................................................2-2 

When to Use Icons.....................................................................................................................2-4 

Ways to Use Icons .....................................................................................................................2-6 

Types of Visual Icons ................................................................................................................2-8 

Composition of an Icon.............................................................................................................2-10 

Sequence of Icon Comprehension ............................................................................................2-12 

 2-1
GENERAL DEVELOPMENT PROCESS FOR IN-VEHICLE ICONS 

Introduction: Reference 1 provides a literature review of icon design principles and design practices and concludes 

that a chief problem in the development of most icons is the lack of a systematic, rigorous design process. 

Reference 2 (from ISO TC 145/SCI DIS 7001) provides a procedure for the development of public information 

symbols that can be useful for developing in-vehicle icons. The design guidelines below have been adapted from

this procedure. 

Design Guidelines

A process for developing in-vehicle icons

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Poor

Response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7) Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7)

Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2)

Testing may be complete.

Proceed as necessary.

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(See Chapter 7)

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see chapter 14)

Does a standard

icon exist?

(see

Does a standard

icon exist?

(

Does a standard

icon exist?

(

Poor

response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see chapter 3)

• Recognizability (see chapter 4)

• Interpretability (see chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see chapter 8)

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(

Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7) Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see chapter 7)

Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see chapter 2)

Testing may be complete.

Proceed as necessary.

Testing may be complete.

Proceed as necessary.

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(See Chapter 7)

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(see chapter 7)

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Poor

Response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Poor

Response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7) Conduct Matching Tests

Use Production Test to

generate ideas for icons

(see Chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7) Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7)

Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2)

Testing may be complete.

Proceed as necessary.

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(See Chapter 7)

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7)

Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2)

Testing may be complete.

Proceed as necessary.

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(See Chapter 7)

Poor

Response?

No Yes

Yes

No

No Yes

Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon Identify in-vehicle message 

requiring an icon

Identify in-vehicle message 

requiring an icon

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see chapter 14)

Does a standard

icon exist?

(see

Does a standard

icon exist?

(

Does a standard

icon exist?

(

Poor

response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see Chapter 15)

Does a standard

icon exist?

(see chapter 14)

Does a standard

icon exist?

(see

Does a standard

icon exist?

(

Does a standard

icon exist?

(

Poor

response?

Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards Consult Relevant Standards

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see Chapter 7)

Conduct Comprehension/

Recognition Tests

(see chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see Chapter 7)

Conduct Appropriateness

Ranking Tests

(see chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see Chapter 7)

Use Production Test to

generate ideas for icons

(see chapter 7)

No Yes

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see chapter 3)

• Recognizability (see chapter 4)

• Interpretability (see chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see chapter 8)

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(

(see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see chapter 3)

• Recognizability (see chapter 4)

• Interpretability (see chapter 5)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Are candidate

icons developed

and/or in use?

(see chapter 8)

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(see

Are candidate

icons developed

and/or in use?

(

Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see Chapter 7) Conduct Matching Tests

(see Chapter 7)

Conduct Matching Tests

(see chapter 7)

Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see Chapter 2) Review general issues in

icon design (see Chapter 2)

Review general issues in

icon design (see chapter 2)

Testing may be complete.

Proceed as necessary.

Testing may be complete.

Proceed as necessary.

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(See Chapter 7)

Testing may be complete. As necessary,

redesign icons and repeat evaluations. 

Consider alternate approaches to evaluations.

(see chapter 7)

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 2-1. General Development Process for In-Vehicle Icons

 2-2
Discussion: The icon development process outlined on the previous page provides a framework for icon design that 

has been organized and used by ISO and is consistent with good design and evaluation practices. The empirical

portions of the guideline have been suggested in a number of data sources (e.g., references 2 and 3), while the 

analytical aspects are consistent with a number of comprehensive sources in the icon development domain (e.g.,

references 4 and 5). 

Evaluating icons refers to the process of determining that an icon, or a set of integrated icons, meets specific criteria 

in areas such as legibility, recognition, interpretation, and driver preferences. Developing useful and effective icons 

requires evaluation. A rigorous and iterative evaluation phase in icon design increases the likelihood that the 

implementation of the icon in the in-vehicle environment will improve driving and system performance and not

degrade driver safety. 

General design principles for the design of in-vehicle icons provide important information that will increase the 

effectiveness and utility of icons. However, they represent only a necessary first step, and cannot take the place of 

empirically assessing the utility of a particular icon. In particular, such principles cannot always consider issues 

such as the driving context, different user groups of icons, or driver workload in selecting icons. That is, using 

general design principles alone cannot assess “specific effectiveness with the potential user group” (reference 6). 

Without research, icon development becomes little more than an intuitive approximation of what constitutes a good

design, and lacks the confidence that can be obtained by empirical validation. 

Design Issues: The development process for in-vehicle icons should reflect the specific needs, goals, and 

constraints associated with individual design efforts. Thus, individual icon design efforts may require additional

tests, design criteria, or consideration of other development issues. 

Cross References:

Chapter 3: Icon Legibility; Chapter 4: Icon Recognition; Chapter 5: Icon Interpretation; Chapter 6: The Auditory 

Presentation of In-Vehicle Information; Chapter 7: Evaluating In-Vehicle Icons; Chapter 8: Icon Collection

References: 

1. Carney, C., Campbell, J. L., and Mitchell, E. A. (1998). In-vehicle display icons and other information

elements. Task A: Literature review (FHWA-RD-98-164). Washington, DC: Federal Highway 

Administration. 

2. Zwaga, H. and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby and 

H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed material (pp. 277-

297). New York: J. Wiley & Sons. 

3. Edworthy, J. (1994). The design and implementation of nonverbal auditory warnings. Applied Ergonomics, 

25(4), 202-210.

4. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: J.

Wiley & Sons. 

5. International Organization for Standardization (ISO) 3461-1. (1988). General principles for the creation of

graphical symbols, Part I: Graphical symbols for use on equipment, Geneva, Switzerland: ISO. 

6. Collins, B. L. (1982). The development and evaluation of effective symbol signs. Washington, DC: U.S. 

Department of Commerce (NBS Building Science Series, 141). 

 2-3
WHEN TO USE ICONS

Introduction: This section considers the criteria and issues that should be considered when determining whether an

icon is the appropriate display element to use for an in-vehicle message. Determining when to use an icon is an

extremely important design decision. In many instances, the use of an icon, instead of text, may be preferable. The

design guideline lists several instances for which this may be true. 

Design Guidelines 

Use icons when: 

• Quick and accurate recognition of a message is necessary (e.g., warnings). 

• Displaying visual or spatial concepts (e.g., augmented signage). 

• The driver will be performing a visual search of alternatives (e.g., motorist services information). 

• The amount of space on the display is limited and presenting the information textually will take up more 

space than is available. 

• One already exists and has a generally accepted meaning. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Icon Design Issue

Quick and accurate

recognition is necessary

Displaying visual or

spatial concepts

Presenting a set of 

alternatives

Do This... ...Not This

CURVES

AHEAD

ROAD

WORK

AHEAD

RESTROOMS GASOLIINE

LODGING TELEPHONE

Icon Design Issue

Quick and accurate

recognition is necessary

Displaying visual or

spatial concepts

Presenting a set of 

alternatives

Do This... ...Not This

CURVES

AHEAD

CURVES

AHEAD

ROAD

WORK

AHEAD

ROAD

WORK

AHEAD

RESTROOMS GASOLIINE

LODGING TELEPHONE

Icon Design Issue

Quick and accurate

recognition is necessary

Displaying visual or

spatial concepts

Presenting a set of 

alternatives

Do This... ...Not This

CURVES

AHEAD

CURVES

AHEAD

ROAD

WORK

AHEAD

ROAD

WORK

AHEAD

RESTROOMS GASOLIINE

LODGING TELEPHONE

Icon Design Issue

Quick and accurate

recognition is necessary

Displaying visual or

spatial concepts

Presenting a set of 

alternatives

Do This... ...Not This

CURVES

AHEAD

CURVES

AHEAD

ROAD

WORK

AHEAD

ROAD

WORK

AHEAD

RESTROOMS GASOLIINE

LODGING TELEPHONE

Figure 2-2. Examples of the Appropriate Use of Icons 

 2-4
Discussion: Well-designed symbols are generally recognized more accurately and quickly than similarly worded

signs (reference 1). Research performed in reference 2 compared subjects’ ability to interpret the meaning of 

symbol and word highway signs. Subjects were asked to match a text sign to one of nine symbol signs they were 

shown on a following film segment. The results of this research showed that, overall, people were able to more 

accurately match symbol signs than they were word signs. Also, 65 percent of the subjects reported that the symbol 

signs were easier to match. Reference 3 found similar results. The researchers investigated subjects’ ability to

correctly identify word and symbol signs and found that they were able to more accurately identify the symbol signs. 

Reference 4 gives three reasons for this: (1) icons are more visually distinct than words; (2) visual symbols have

names that we remember along with them, thus they are stored as both visual and verbal memories whereas text 

labels are stored only verbally; and (3) visual images are stored in memory in several forms and are tightly linked to

one another and to other forms. 

Another reason to use icons is that they can be presented in a much more spatially condensed form (references 5, 6, 

and 7) than can most text-based messages. This is especially important to consider when designing in-vehicle 

displays where the amount of room available is extremely limited. Road signs also have a limited amount of space

for presenting information, and must take advantage of the fact that more information can be presented to the driver

via icons and symbols than can be presented textually. Research in this domain has shown that symbols can be 

recognized more rapidly and are legible at greater distances than information presented in other formats (references

8 and 9). 

Design Issues: Research has shown that while well designed symbols perform better than text (reference 1), poorly

designed symbols do not (reference 5). Care should be taken to ensure that the symbols used are effective and that 

comprehension levels are high. Therefore, extensive testing should be done (such as that described in chapter 7 of

this document) on every newly developed symbol, and even on some of those already in existence, when

comprehension levels do not meet the ISO standard of 66 percent (reference 10).

Cross References:

Ways to Use Icons, p. 2-6 

References:

1. Edworthy, J., and Adams, A. (1996). Warning design: A research prospective. London, U.K.: Taylor and 

Francis. 

2. King, L. E. (1971). A laboratory comparison of symbol and word roadway signs. Traffic Engineering and

Control, 12, 518-520.

3. Walker, R. E., Nicolay, R. C., and Stearns, C. R. (1965). Comparative accuracy of recognizing American and 

international road signs. Journal of Applied Psychology, 49(5), 322-375.

4. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

5. Zwaga, H. J., and Boersema, T. (1983). Evaluation of a set of graphic symbols. Applied Ergonomics, 14(1), 43-

54. 

6. Rohr, G., and Keppel, E. (1984). Iconic interfaces: Where to use and how to construct human factors in

organisational design and management. The Netherlands: North-Holland. 

7. Hemenway, K. (1982). Psychological issues in the use of icons in command menus. Proceedings of the CHI 

1982 Conference on Human Factors in Computer Science (pp. 20-23). New York: Association for 

Computing Machinery.

8. Ells, J. G., and Dewar, R. E. (1979). Rapid comprehension of verbal and symbolic traffic sign messages. 

Human Factors, 21(2), 161-168. 

9. Jacobs, R. J., Johnston, A. W., and Cole, B. L. (1975). The visibility of alphabetic and symbolic traffic signs. 

Australian Road Research, 5(7), 68-86. 

10. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby

and H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed materials (pp. 

277-297). New York: J. Wiley & Sons. 

 2-5
WAYS TO USE ICONS

Introduction: Icons may be used in a wide variety of ways to facilitate interaction with an in-vehicle information system (IVIS). 

Icons may alert drivers and guide their attention to a deviation or event. They can identify system status or acceptable 

alternatives, or support comparisons for selecting among alternatives. In addition, icons can help drivers take appropriate actions 

when used to label controls. Each of these general information processing functions has different icon-design requirements. 

Design Guidelines 

Information Processing 

Element

Potential Icon

Applications

Examples Important Guideline Topics To Consider 

for Effective Icon Design

Attention: Verifying process 

proceeds according to plan and 

directing attention to 

deviations

Icons that provide 

cautions and warnings 

Collision avoidance 

Icy road warning

Augmenting icons with auditory information 

(p. 6-2)

Flash rate (p. 4-8)

Conveying urgency with icons (p. 5-14)

Enhancing icon interpretation with color 

(p. 5-12)

Interpretation: Identifying a 

status or scanning potential 

alternatives

Icons that highlight

changes in system state

Distance remaining for route 

Toll cost

Enhancing icon interpretation with text labels 

(p. 5-2)

Conveying system status with icons (p. 5-10)

Enhancing icon interpretation with color 

(p. 5-12)

Selection: Comparing 

alternatives, determining the 

effect each will have on the 

end goal, and choosing one to 

meet those goals

Icons for trip planning and 

route selection

Congestion related delay

Hotel costs and availability

Identifying icons as part of a group (p. 5-8)

Enhancing icon interpretation with color 

(p. 5-12)

Action: Selecting system

functions and timing tasks to 

achieve an end goal

Icons that label controls 

and identify system

features

Select route 

Retrieve message

Conveying the effect of actions with icons 

(p. 5-6)

Identifying icons as part of a group (p. 5-8)

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

The figure to the left shows nine Infrastructure

Processing Elements (IPE) that define the information 

requirements of a driver interacting with an IVIS device. 

These elements comprise a decision cycle represented by 

the circle. Between each IPE, phrases in italics identify a 

knowledge state that acts as the input to one element and

the output of the previous element. Together, the nine 

elements describe the range of information-processing 

activities supported by IVIS messages. The decision 

cycle consists of four quadrants, with the IPEs within 

each quadrant serving a common purpose. The first 

quadrant, “Attention,” involves detecting disturbances 

and deviations, and directing attention towards the 

disruption. The second quadrant, “Interpret,” builds upon 

this to classify and understand attended inputs. The third 

quadrant, “Selection,” uses this interpreted information to

identify an appropriate course of action. The fourth 

quadrant, “Action,” carries out the course of action. Each 

quadrant helps identify general design requirements for

supporting driver decisions and the IPEs within each 

quadrant identify specific requirements 

Attention Interpretation

Action Selection

MONITOR

Attention to

Deviation/Event

Deviation/Event

IDENTIFY

SEARCH

EVALUATE

Desired

Alternative

Acceptable 

Alternatives

PLAN

COORDINATE DECIDE

CONTROL

Action on System and 

Expected Response

Absolute or Relative

Task Timing

Related Set of Tasks

ALERT

1

4

2

3

Intended Tasks

Status or Categorized 

Alternatives

Attention Interpretation

Action Selection

MONITOR

Attention to

Deviation/Event

Deviation/Event

IDENTIFY

SEARCH

EVALUATE

Desired

Alternative

Acceptable 

Alternatives

PLAN

COORDINATE DECIDE

CONTROL

Action on System and 

Expected Response

Absolute or Relative

Task Timing

Related Set of Tasks

ALERT

1

4

2

3

Intended Tasks

Status or Categorized 

Alternatives

Attention Interpretation

Action Selection

MONITOR

Attention to

Deviation/Event

Deviation/Event

IDENTIFY

SEARCH

EVALUATE

Desired

Alternative

Acceptable 

Alternatives

PLAN

COORDINATE DECIDE

CONTROL

Action on System and 

Expected Response

Absolute or Relative

Task Timing

Related Set of Tasks

ALERT

1

4

2

3

Intended Tasks

Status or Categorized 

Alternatives

Attention Interpretation

Action Selection

MONITOR

Attention to

Deviation/Event

Deviation/Event

IDENTIFY

SEARCH

EVALUATE

Desired

Alternative

Acceptable 

Alternatives

PLAN

COORDINATE DECIDE

CONTROL

Action on System and 

Expected Response

Absolute or Relative

Task Timing

Related Set of Tasks

ALERT

1

4

2

3

Intended Tasks

Status or Categorized 

Alternatives

Figure 2-3. Information Processing Elements Used to Identify Icon Requirements

 2-6
Discussion: The information processing perspective has long provided a useful tool to describe human-machine 

coordination (references 1, 2, and 3). Developed to describe human interaction with complex systems, Rasmussen’s 

decision ladder provides one of the more detailed accounts of human-machine information processing. The decision 

ladder breaks the decision process into eight elements that describe the mental activities that link environmental cues 

to actions. More recently, reference 4 adapted Rasmussen’s decision ladder and Miller’s (references 5 and 6) 

information processing taxonomy to describe driver interaction with Advanced Traveler Information System (ATIS) 

devices. This description helped identify the driver limits and capabilities that are relevant for particular ATIS 

functions. This revised decision cycle consists of four quadrants, discussed on the previous page. IVIS messages 

may span more than one information processing element or quadrant of the figure, but these distinctions provide an

initial guide for investing icon development resources. 

Design Issues: The design requirements of an icon depend on the information processing it is meant to support. 

IVIS messages associated with “Attention” require an icon that can attract attention and direct it to the event of 

concern. Design issues include the size and placement of the icon, as well as the use of flashing and auditory cues to

attract attention. IVIS messages associated with “Interpretation” require icons that can be easily linked to the 

potentially complex messages they seek to convey. Design issues include the use of text labels to avoid ambiguity 

and the need to use icons that are familiar to many people. IVIS messages associated with “Selection” require that

icons enable drivers to clearly understand various options and alternate plans. Design issues include grouping icons 

so that differences can be easily seen and compared. IVIS messages associated with “Action” should indicate 

available options and indicate the consequences of pressing a button or selecting a menu option. Design issues 

include the need to convey the effect of an action or the sequence of activities that will result from enacting a system

function. The figure on the previous page summarizes the four information processing functions and the associated

design guidelines. 

Cross References:

When to Use Icons, p. 2-4; Flash Rate, p. 4-8; Chapter 5: Icon Interpretation; Augmenting Icons with Auditory 

Information, p. 6-2 

References:

1. Broadbent, D. E., and Gregory, M. (1963). Division of attention and the decision theory of signal detection.

Proceedings of the Royal Society B, 158, 222-231. 

2. Neisser, U. (1967). Cognitive psychology. New York: Meredith Publishing Co. 

3. Rasmussen, J. (1986). Information processing and human-machine interaction: An approach to cognitive 

engineering. New York: North-Holland.

4. Lee, J. D., Morgan, J., Wheeler, W. A., Hulse, M. C., and Dingus, T. A. (1997). Development of human factors 

guidelines for advanced traveler information systems and commercial vehicles: ATIS and CVO functional

description (FHWA-RD-95-201). Washington, DC: Federal Highway Administration. 

5. Miller, R. B. (1971). Development of a taxonomy of human performance: Design of a systems task vocabulary

(AIR-72/6/2053-3/71-TRII). Washington, DC: American Institute for Research. 

6. Miller, R. B. (1974). A method for determining task strategies (AFHRL-TR-74-26). Washington, DC: 

American Institute for Research. 

 2-7
TYPES OF VISUAL ICONS

Introduction: “Types of icons” refers to the classification of a particular icon based upon its resemblance to the 

message or referent. An icon can be classified three ways: image-related, concept-related, or arbitrary. 

1. “Image-related icons” are highly pictorial representations of the object or act they represent. 

2. “Concept-related icons” are based on an example or property of a real object or action.

3. “Arbitrary icons” do not resemble the object or action they represent, but become meaningful only through

convention and education. 

These three icon types have important and different implications for icon development and design. 

Design Guidelines 

“Image-related icons” are directly comprehended and should be used wherever possible. 

“Concept-related icons” can be used if the user can be expected to comprehend the context in which the icon is

presented.

“Arbitrary icons” can be difficult to recognize, hard to learn, and hard to remember. They should only be used if

both context and special knowledge are present. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Image-Related

Arbitrary

Concept-Related

Telephone ahead Gas station ahead

Curve signs Elevator

Icon Type Other Examples

U.S. Postal Service

Key Examples

Fasten seat belt

Flash function on a camera

or high voltage symbol

in a power plant

Addition symbol, first aid

symbol, or international

symbol for the Red Cross Medical profession

Image-Related

Concept-Related

Icon Type Key Examples Other Examples

Image-Related

Arbitrary

Concept-Related

Telephone ahead Gas station ahead

Curve signs Elevator

Icon Type Other Examples

U.S. Postal Service

Key Examples

Fasten seat belt

Flash function on a camera

or high voltage symbol

in a power plant

Addition symbol, first aid

symbol, or international

symbol for the Red Cross Medical profession

Image-Related

Concept-Related

Icon Type Key Examples Other Examples

Figure 2-4. Types of Icons 

 2-8
Discussion: Icons are visual representations or images used to symbolize an object, action, or concept. Several 

authors have classified icons into three different types: image-related (pictorial), concept-related (analogical), and

arbitrary (see references 1 through 5). Image-related icons are highly pictorial representations of the object or act 

they represent. For these types of icons, meaning can be derived directly from the icon itself. For example, a seat 

belt icon usually appears whenever the ignition is started in a vehicle. This simply alerts drivers to the fact that they 

should be wearing their seat belt. This type of icon refers directly to the object it resembles and is therefore the 

easiest for people to remember and takes almost no effort to learn.

Concept-related icons are based on an example or a property of a real object or action. In most instances, the 

meaning of these types of icons will change depending upon the context that it is presented in. For instance, a 

lightning bolt symbol that is shown on a camera usually represents the flash function. However, when the lightening 

bolt symbol is seen in a different context, perhaps while touring an electrical plant, it might be indicating a high

voltage area. Because the meaning of these icons changes depending on the context they are viewed under, they are 

slightly more difficult for people to learn. 

Arbitrary icons do not resemble the object or action they represent, but become meaningful only through convention 

and education. A good example of an arbitrary icon is the Red Cross symbol, which generally refers to the concept

of emergency first aid. To someone from another culture, however, it may have an entirely different meaning or it

may have no meaning at all. For example, if you are not aware of this symbol’s link to medicine or emergency first

aid, you may simply see it as a symbol for addition or perhaps as a religious cross. However, if you are aware of

this link, you may recognize it as the international symbol for the Red Cross. Therefore, it is necessary, in most 

cases, to have a particular knowledge base before being able to derive the correct meaning from these types of icons.

This makes them the most difficult for people to learn and to remember. 

Design Issues: These distinctions among icon types are important because they allow us to make predictions about

an icon’s interpretation and overall utility. Interpretation of an image-related icon may be high if the icon is a clear, 

straightforward representation of the message it represents. Interpretation of context-related icons may be high if the 

user understands the situation and condition associated with presentation of the icon. Interpretation of arbitrary 

icons requires both context and knowledge, yet they are very powerful and flexible. 

Cross References: 

Ways to Use Icons, p. 2-6 

References: 

1. Lodding, K. N. (1983). Iconic interfacing. IEEE Computer Graphics and Applications, 3(2), 11-20.

2. Rogers, Y. (1989). Icon design for the user interface. International Reviews of Ergonomics, 2, 129-154. 

3. Modley, R. (1976). Handbook of pictorial symbols. New York: Dover Press. 

4. Beardon, C. (1992). Computer-based iconic communication. In K. Ryan and R. Sutcliffe (Eds.), AI and 

cognitive science 1992 (pp. 263-276). New York: British Computer Society. 

5. Bliss, C. K. (1965). Semantography. Australia: Semantography Publications. 

 2-9
COMPOSITION OF AN ICON

Introduction: An icon comprises several parts. These components work together to increase the likelihood that 

users will understand the icon. 

Design Guidelines 

Border • Use to show the extent of an icon (beginning and end). 

Background • Don’t cover more than half the available area with objects.

• Avoid patterns in the background. 

• Put the image clearly in front of the background. 

• Place objects in the center and the background around the periphery. 

• Use unsaturated, cool colors for the background, and saturated, warm colors for the foreground

image. 

• Keep the background static; if anything blinks or moves, the viewer perceives it as a

foreground image. 

• Limit the background image to a simple rendition of a recognizable, concrete object. 

Element • Use commonly accepted or standardized elements when possible. 

• Elements should reflect design principles described in chapter 4.

Symbol

(Shapes)

• Circles should be used for presenting prohibition or mandatory information. 

• Triangles or diamonds should be used to present warning or cautionary information. 

• Squares or triangles should be used to present general information, instructions, or safe 

condition information.

Text Label • Use only when necessary, especially when the icon is concept-related or arbitrary. 

• Keep text to no more than two-three words. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Border

Background

Element

Text label

Symbol

Border

Background

Element

Text label

Symbol

WARNING

Figure 2-5. Key Components of an Icon 

 2-10 
Discussion: Reference 1 has provided an overview of key parts of icons. Borders show the extent of an icon (i.e., 

where it begins and where it ends). This can be important to interactive systems that use icons as control buttons. In

such instances, a border might help the user determine exactly where to click or point to select an icon. They also 

make icons appear orderly, consistent, and uniform. Borders can help clarify an icon’s meaning if it resembles a 

familiar object (i.e., a book or an engine symbol). However, there are some drawbacks associated with using 

borders. They can make icons less distinctive, compete with the image, and limit the size of the image that can be

used (see reference 2). 

The use of a background is not always seen as being an important part of icon design. However, when used

appropriately, backgrounds can help emphasize the image, group or classify icons, or show the state of an icon. 

Shapes are also important for icon design because they can convey meaning. This is particularly true of traffic 

signs. According to the Manual on Uniform Traffic Control Devices (MUTCD), “STOP” signs are octagonal in

shape; “YIELD” signs are equilateral triangles pointing downward; other regulatory signs are rectangular in shape 

with the longer dimension vertical; and warning signs are generally diamond-shaped. Having certain shapes 

designated for specific types of signs can help reduce both recognition and response times (references 3, 4). 

Design Issues: Reference 1 suggests that presenting text labels in addition to an icon is a good idea when the icon is 

not obvious or if it is being presented for the first time. Research has shown that presenting the two together can 

increase comprehension and therefore overall effectiveness. For example, in reference 5, a study compared people’s

ability to navigate through a database using either pictorial icons, text labels, or a combination of the two. The 

results showed that subjects were able to reach the target object much quicker and with fewer steps in the icon plus 

text condition. Another study (reference 6) found similar results when it examined the role of graphics in the 

selection of items from a menu. Specifically, the study found that text plus graphics greatly reduced the number of

errors in the selection of the correct item. 

Cross References: 

Level of Detail, p. 4-4; Perceptual Principles of Icon Design, p. 4-6; Design of Prohibition Symbols, p. 4-10;

Enhancing Icon Interpretation with Text Labels, p. 5-2; Identifying Icons as Part of a Group, p. 5-8;

Conveying System Status with Icons, p. 5-10

References: 

1. Carney, C., Campbell, J. L., and Mitchell, E. A. (1998). In-vehicle display icons and other information

elements. Task A: Literature review (FHWA-RD-98-164). Washington, DC: Federal Highway 

Administration. 

2. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

3. ISO 3864. (1984). International standard for safety colours and safety signs. Geneva, Switzerland: ISO. 

4. AS 2342. (1992). Development, testing, and implementation of information and safety symbols and symbolic 

signs. Sydney, Australia: Standards Australia. 

5. Edigo, C., and Patterson, J. (1988). Pictures and category labels as navigational aids for catalog browsing. 

Human Factors in Computing Systems: CHI ‘88 Conference Proceedings, 127-132.

6. Muter, P., and Mayson, C. (1986). The role of graphics in item selection for menus. Behaviour and Information

Technology, 5(1), 89-95. 

 2-11 
SEQUENCE OF ICON COMPREHENSION

Introduction: Sequence of icon comprehension refers to the perceptual and cognitive process by which users 

interpret the meaning of an icon. As discussed in reference 1, three stages appear to be associated with icon 

comprehension and use: legibility, recognition, and interpretation. Legibility reflects the relationships among the 

driver, the icon, and the environment; it is essential for the initial perception of the icon and includes parameters 

such as luminance uniformity, contrast, and icon size. Recognition reflects the relationships among the driver, the 

icon, and the other icons or visual display elements; it includes parameters such as whether or not the driver can

identify the icon, especially in the context of the symbols and icons. Interpretation reflects the relationships among

the driver, the icon, and the referent or message associated with the icon; it includes parameters such as whether the 

driver comprehends the meaning, intent, or purpose of the icon. 

Design Guidelines 

Stage of Icon Comprehension Design Parameters to Consider 

Legibility Determining the appropriate luminance uniformity in an icon; determining the 

appropriate contrast in an icon; determining the appropriate size of icon

components; designing effective text labels, and the effects of color on icon

legibility 

Recognition Level of realism, level of detail; perceptual principles of icon design; flash

rate; design of prohibitive symbols; and driver acceptance of general versus 

specific icons 

Interpretation Enhancing icon interpretation with text labels; composition of text labels; 

conveying the effect of actions with icon; identifying icons as part of a group;

conveying system status with icons; enhancing icon interpretation with color; 

conveying urgency with icons; and enhancing icon interpretation with shape 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Recognition

• Can the driver see the icon?

• Is it legible at various distances?

• Can it be seen under both nighttime

and daytime lighting conditions?

• How well do the parts of this symbol

relate to one another?

• Does the construction of the symbol

support accurate recognition?

• Is it easily confused with other symbols?

• How well does the icon represent the message?

• Will it be understood when presented in the

appropriate context?

• Does it require special knowledge particular

to a culture, language, or driver age?

Legibility Interpretation

See Chapter 3 See Chapter 4 See Chapter 5

Recognition

• Can the driver see the icon?

• Is it legible at various distances?

• Can it be seen under both nighttime

and daytime lighting conditions?

• How well do the parts of this symbol

relate to one another?

• Does the construction of the symbol

support accurate recognition?

• Is it easily confused with other symbols?

• How well does the icon represent the message?

• Will it be understood when presented in the

appropriate context?

• Does it require special knowledge particular

to a culture, language, or driver age?

Legibility Interpretation

See Chapter 3 See Chapter 4 See Chapter 5

Recognition

• Can the driver see the icon?

• Is it legible at various distances?

• Can it be seen under both nighttime

and daytime lighting conditions?

• How well do the parts of this symbol

relate to one another?

• Does the construction of the symbol

support accurate recognition?

• Is it easily confused with other symbols?

• How well does the icon represent the message?

• Will it be understood when presented in the

appropriate context?

• Does it require special knowledge particular

to a culture, language, or driver age?

Legibility Interpretation

See Chapter 3 See Chapter 4 See Chapter 5

Figure 2-6. Sequence of Icon Comprehension and Use 

 2-12 
Discussion: Developing effective icons and symbols requires a conceptual approach that applies a theoretical 

understanding of driver perception and performance (reference 2). Past research has demonstrated that if they are 

designed appropriately, visual symbols and icons can be a very effective way to communicate information to the 

driver. Less definitive information is available on how to design effective icons and symbols. 

As shown in the graphic on the previous page, there seem to be three stages associated with icon comprehension and 

use. The first stage, legibility, reflects the relationship between the driver, the icon, and the environment. It 

includes basic issues such as whether or not the driver can see the icon, given the normal range of lighting and

viewing conditions associated with driving. Legibility will depend on icon design issues such as luminance 

uniformity, contrast, icon size, text labels, and the effective use of color. 

The second stage, recognition, reflects the relationship between the driver, the icon, and other icons or visual display 

elements. It includes issues such as whether the driver can identify the icon, especially in the context of other 

symbols and icons. For example, the standard icon for fuel depicts a gas pump. Accurate recognition of this icon

would mean that the driver recognizes it as a gas pump. Recognition will depend on design issues such as level of

realism, level of detail, perceptual principles of icon design, and flash rate.

The third stage, interpretation, reflects the relationship between the driver, the icon, and the referent or message

associated with the icon. It includes issues such as whether the driver comprehends the meaning, intent, or purpose 

of the icon. For example, using the “gas pump” icon described above as an example, successful interpretation would

mean that the driver understands what the icon’s message is—the vehicle is low on fuel. Interpretation will depend

on design issues such as the use of text labels, conveying the effect of actions with icons, identifying icons as part of

a group, conveying system status with icons, the use of color in icons, and conveying urgency with icons. 

Design Issues: After periods of exposure and use, drivers can learn to recognize virtually any icon; even ones that

bear little relationship to their associated message. Thus, while even “bad” icons can eventually be effective, they 

may promote errors, require training, or involve extensive trial-and-error learning. 

Cross References: 

Chapter 3: Icon Legibility; Chapter 4: Icon Recognition; Chapter 5: Icon Interpretation

References:

1. Carney, C., Campbell, J. L., and Mitchell, E. A. (1998). In-vehicle display icons and other information

elements. Task A: Literature review (FHWA-RD-98-164). Washington, DC: Federal Highway 

Administration. 

2. Kantowitz, B. H. (1997, March). In-vehicle information systems: Premises, promises, and pitfalls. Paper

presented at the Transportation Research Board Conference on Intelligent Transport Systems, Highway 

Safety and Human Factors, Washington, DC. 

 2-13 
 

CHAPTER 3: ICON LEGIBILITY 

Determining the Appropriate Luminance Uniformity within an Icon.......................................3-2 

Determining the Appropriate Contrast within an Icon .............................................................. 3-4 

Determining the Appropriate Size of Icon Components............................................................3-6 

Designing Effective Text Labels ...............................................................................................3-8 

The Effects of Color on Icon Legibility....................................................................................3-10

 3-1
DETERMINING THE APPROPRIATE LUMINANCE UNIFORMITY WITHIN AN ICON 

Introduction: Luminance uniformity refers to the consistency of luminance values across an icon. Moderate 

nonuniformities in luminance may only lead to the driver’s perception that the display is of poor quality. With great 

nonuniformities in luminance, however, there may not be sufficient luminance and contrast to ensure adequate

legibility in certain areas of the display. 

Design Guidelines 

Provide no more than 33 percent element nonuniformity (within an individual element or segment). 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Luminance A Luminance B

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Nonuniformity

= 

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Luminance A Luminance B

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Nonuniformity

= 

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Luminance A Luminance B

Within a segment or element of an icon, measure at two

locations using a photometer with a spot size small

enough to fit inside the segment or element.

% Element

Nonuniformity

= 

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

% Element

Nonuniformity

= 

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

(1) % Element

Nonuniformity

= 

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

|(Luminancemin) - (Luminancemax)|

(Luminancemax)

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Figure 3-1. Measuring Luminance Nonuniformity

 3-2
Discussion: Threshold Luminance Discrimination Data. Although observers in reference 1 could discriminate 

lights that differed in luminance by as little as 10 percent, these data were obtained when they were trying to detect a 

luminance difference between a background and a target under ideal laboratory conditions (also see reference 2). 

Thus, 10 percent represents a threshold luminance discrimination value and is far too conservative for IVIS use, in

which the issue of concern is the driver’s ability to notice luminance differences under normal driving or normal 

viewing conditions. 

Tolerance for Luminance Variations. Reference 3 indicates that luminance in cathode ray tubes (CRTs) typically 

varies by as much as 37 percent and is either not noticed or is considered to be acceptable by observers. Reference 4 

recommends that luminance variations remain below 50 percent. Reference 5 indicates that while the preferred limit 

for luminance variation across optical projection displays is 33 percent, an unacceptable limit is 66 percent. 

Conclusions. The design guidelines reflect a composite of the information provided by references 3, 4, and 5. 

Specifically, luminance differences up to 37 percent are not always noticed by observers, and 33 percent represents a 

preferred limit, therefore 33 percent seems to be an acceptable limit for small-area luminance nonuniformities (i.e., 

within an individual element or segment). Both 50 percent and 66 percent have been suggested as absolute upper 

limits on luminance nonuniformities.

Design Issues: Luminance nonuniformities are generally caused by the display itself. In vacuum fluorescent 

displays (VFDs) being viewed directly, for example, these might be caused by poor phosphor distribution on the 

inside of the anodes, or by fluctuations in the power supply output. 

Cross References: 

Determining the Appropriate Contrast within an Icon, p. 3-4 

References: 

1. Mueller, C. G. (1951). Frequency of seeing functions for intensity discrimination at various levels of adapting 

intensity. Journal of General Psychology, 34, 463-474. 

2. Boff, K. R., Kaufman, L., and Thomas, J. P. (1986). Handbook of perception and human performance. New 

York: J. Wiley & Sons. 

3. Farrell, R. J., and Booth, J. M. (1984). Design handbook for imagery interpretation equipment. Seattle, WA: 

Boeing Aerospace Company. 

4. American National Standards Institute. (1988). American national standard for human factors engineering of

visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society. 

5. MIL-STD-1472D. (1989). Human engineering design criteria for military systems, equipment and facilities. 

Washington, DC: U.S. Government Printing Office. 

 3-3
DETERMINING THE APPROPRIATE CONTRAST WITHIN AN ICON

Introduction: Contrast refers to the relationship between the luminance of a symbol and the luminance of its

background. Contrast requirements have not been empirically studied under a wide range of representative driving 

situations and conditions, thus few empirical data can be directly used to specify design guidelines. 

We define contrast as a ratio between maximum and minimum luminance values, or: (2) 

Contrast ratio = Luminance max

 ____________________

Luminance min

where: 

Luminance max = luminance emitted by the area or element of greater intensity 

Luminance min = luminance emitted by the area or element of smaller intensity 

Design Guidelines 

3:1 Minimum symbol contrast

7:1 Preferred symbol contrast

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

The figure below may be used to aid contrast measurements. 

NOTE: The spot size of the photometer used to take luminance measurements must be small enough to fit 

inside the icon elements being measured. 

Measure at these 3 points and average

readings to obtain Luminance minimum

Measure at these 3 points and average

readings to obtain Luminance maximum

Measure at these 3 points and average

readings to obtain Luminance minimum

Measure at these 3 points and average

readings to obtain Luminance maximum

Measure at these 3 points and average

readings to obtain Luminance minimum

Measure at these 3 points and average

readings to obtain Luminance maximum

Figure 3-2. Example of Measuring Contrast 

 3-4
Discussion: Contrast requirements can vary greatly as a function of display medium (e.g., electronic display vs. 

hardcopy), viewing environment (e.g., low vs. high glare), and user characteristics (e.g., young vs. older drivers). 

Most human factors reference sources that provide contrast recommendations do not address the effects of these and 

other variables on contrast requirements. Reference 1 describes a series of studies investigating the legibility of

displays, and concludes that contrast ratios of 10:1 to 18:1 are required for visual display terminal (VDT) displays. 

Reference 2 indicates that a contrast ratio of 10:1 has become “a generally accepted industrial standard for display 

design.” Reference 3 suggests that a contrast ratio of 7:1 is preferred, but that 3:1 is required; the guidelines given 

here reflect the recommendations in reference 3. However, other data sources suggest that far less contrast may be 

adequate. 

Daytime. An ambient background luminance of 2500 foot lamberts (fLs) is considered to be a representative “worst 

case” background luminance for daytime driving. Reference 4 indicates that symbol contrast of 1.2:1 is sufficient

for young military pilots. In reference 5, contrast requirements for both younger and older subjects were

investigated under laboratory conditions. The data from reference 5 indicate that 1.4:1 contrast may be sufficient for 

older drivers under those conditions. 

Nighttime. In reference 6, contrast requirements for both younger and older subjects were investigated under low

luminance laboratory conditions. The data obtained in reference 6 indicated that 2:1 contrast is required for older 

drivers under low luminance conditions; in this study, adequate legibility was not obtained at contrast levels below 

2:1 (i.e., 1.25:1). 

Design Issues: The contrast ratios provided above will lead to adequate legibility as long as other design

parameters, such as icon size and luminance, are sufficient. Older drivers generally have poorer visual acuity than 

do younger drivers. Thus, the design guidelines specified above assume that, all other factors being equal, design

objectives for contrast that meet the legibility needs of older drivers will always meet the legibility needs of younger 

drivers.

Cross References:

Determining the Appropriate Luminance Uniformity within an Icon, p. 3-2; Determining the Appropriate Size of

Icon Components, p. 3-6 

References: 

1. Shurtleff, D. A. (1980). How to make displays legible. La Mirada, CA: Human Interface Design. 

2. Smith, M. J., and Cohen, W. J. (1997). Chapter 50: Design of computer terminal workstations. In G. Salvendy 

(Ed.), Handbook of human factors and ergonomics (pp. 1637-1688). New York: J. Wiley & Sons. 

3. American National Standards Institute. (1988). American national standard for human factors engineering of

visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society. 

4. MIL-D-87213A. (1986). Military specification displays, airborne, electronically/optically generated. 

Washington, DC: U.S. Government Printing Office. 

5. Blackwell, O. M., and Blackwell, H. R. (1971). Visual performance data for 156 normal observers of various 

ages. Journal of the Illuminating Engineering Society, October, 3-13. 

6. Mourant, R. R., and Langolf, G. D. (1976). Luminance specifications for automobile instrument panels. Human

Factors, 18(1), 71-84.

 3-5
DETERMINING THE APPROPRIATE SIZE OF ICON COMPONENTS

Introduction: Size of icon components refers to the visual angle subtended (at the driver’s eye) in minutes of arc, by either the 

symbol or the text that comprises an icon. Determining the adequate size for a legible icon is extremely important as the amount 

of space available for advanced in-vehicle display icons and other information elements is very limited. 

Design Guidelines

• The visual angle of symbols contained within an icon: 

optimum visual angle = 1.43 degrees (85 arcmin.)

minimum visual angle = 0.69 degrees (41 arcmin.)

• The visual angle of text labels contained within an icon: 

optimum visual angle = 0.40 degrees (24 arcmin.)

minimum visual angle = 0.27 degrees (16 arcmin.)

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 3-1. Determining the Appropriate Size of Icon Components 

Use These Formulas for Calculating These Unknowns

If Known 

Visual Angle Symbol Height Distance 

Distance and 

Symbol Height 

(3) 

or

(4) 

– –

Distance and 

Visual Angle 

– 

(5) 

– 

Visual Angle and 

Symbol Height 

– –

(6) 

Arctan Symbol Height

Distance

Distance

3438 (Height) ÷ 60

Distance

3438 (Height)

Distance

3438 (Height) ÷ 60

Distance H [Tangent (Visual Angle)]

Tangent (Visual Angle)

Symbol Height

where: Symbol Height = the height of the symbology

Distance = distance from viewer’s eyepoint to the display 

Visual Angle = angle in degrees 

Height and Distance use the same unit of measure 

Symbol

Height

Visual Angle

Eyepoint Distance from viewer to display

Figure 3-3. Relationship Between Viewing Distance, Symbol Height, and Visual Angle

 3-6
Discussion: The design guidelines for symbol size are consistent with the recommendations made by reference 1, 

which were based on a variety of research related to detection and resolution thresholds. The maximum visual angle 

suggested (85 arcminutes) is aimed at ensuring conspicuity, while the minimum visual angle (41 arcminutes) simply 

ensures legibility. It is important to note that the recommendations made in reference 1, and therefore the guidelines 

on the previous page, are based on the assumption that the symbol will not be placed outside a 15-degree angular 

displacement from the central line of the normal direction of user’s vision. 

Design guidelines regarding the size of text labels is supported by reference 2, which recommends an optimum

character height of 24 arcminutes of visual angle. In addition, references 3, 4, and 5 investigated symbology height

requirements as a function of various levels of contrast and luminance. Considered as a whole, the empirical data 

from these studies indicate that: (1) critical symbology should subtend at least 20 arcminutes; (2) legibility begins to

decrease at less than about 18 arcminutes; and (3) designers should avoid using symbology that subtends less than

16 arcminutes. Given the consistent and static nature of text labels for icons, the minimum visual angle of text

labels (16 arcminutes) reflects these recommendations. 

Reference 6 indicates that the minimum size of graphical symbols is 1/100th their viewing distance, which 

corresponds to 0.57 degrees visual angle. Icons presented using a dot-matrix display technology (e.g., CRT or LCD)

are typically 16x16 or 32x32 pixels in size (reference 7). Also, reference 8 notes that selecting an appropriate size 

for an icon depends on the input device used within the system. For example, icons that will be selected using a 

mouse or a track ball should be at least 20x20 pixels, and icons that will be selected using a stylus or a pen should be

at least 15x15 pixels. 

Design Issues: Older drivers generally have poorer visual acuity than do younger drivers. Thus, the design

guidelines specified above assume that, all other factors being equal, design objectives for symbol height that meet

the legibility needs of older drivers will always meet the legibility needs of younger drivers. 

Cross References:

Determining the Appropriate Contrast within an Icon, p. 3-4; Designing Effective Text Labels, p. 3-8 

References:

1. International Organization for Standardization (ISO)/TR 7239. (1984). Development and principles for 

application of public information symbols. Geneva, Switzerland: ISO. 

2. American National Standards Institute. (1988). American national standard for human factors engineering of

visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society. 

3. Mourant, R. R., and Langolf, G. D. (1976). Luminance specifications for automobile instrument panels. Human

Factors, 18(1), 71-84.

4. Howell, W. C., and Kraft, C. L. (1959). Size, blur, and contrast as variables affecting the legibility of alphanumeric symbols on radar-type displays (WADC Technical Report 59-536). Wright-Patterson Air Force 

Base, OH: Wright Air Development Center (DTIC No. AD-232 889). 

5. Giddings, B. J. (1972). Alpha-numerics for raster displays. Ergonomics, 15(1), 65-72.

6. ISO 3461-1. (1988). General principles for the creation of graphical symbols, Part I: Graphical symbols for use 

on equipment. Geneva, Switzerland: ISO. 

7. Fowler, S. L., and Stanwick, V. R. (1995). The GUI style guide. New York: Academic Press. 

8. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

 3-7
DESIGNING EFFECTIVE TEXT LABELS

Introduction: Text labels refer to words or phrases, as well as all other numerical and character symbols, provided

as part of an icon that act to define or clarify its meaning. 

Design Guidelines 

• Text labels should be brief, no more than 2-3 words. 

• The type should be at least 0.27 degrees of visual angle (16 arcmin.); 0.40 degrees (24 arcmin.), maximum.

• Use a clear and simple sans serif typeface such as Helvetica. Avoid using boldface, italics, underlining, or 

differences of color to emphasize words. 

• The space between lines should be at least 1/30 the line length. 

• Use both uppercase and lowercase letters rather than all of one or the other. 

• Character width-to-height ratios should be 0.6:1 - 1:1 (width:height). 

• Wider characters should be used as criticality increases. 

• If text must be compressed, compress the space between characters rather than the characters (1). 

• Use initial capital letters for multiword labels not incorporated in the symbol. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Low Clearance Ahead

Effective Use of Text Label

Overheight vehicles take another route around restricted clearance.

Ineffective Use of Text Label

Use initial capital letters

when the label is not part

of the symbol.

Avoid using italics

to emphasize words.

The space between lines should be

at least 1/30 the line length.

Make the type >0.27 degrees

visual angle.

Use a clear and

simple font.

Low Keep text labels brief. Clearance Ahead

Effective Use of Text Label

Overheight vehicles take another route around restricted clearance.

Ineffective Use of Text Label

Use initial capital letters

when the label is not part

of the symbol.

Avoid using italics

to emphasize words.

The space between lines should be

at least 1/30 the line length.

Make the type >0.27 degrees

visual angle.

Use a clear and

simple font.

Low Keep text labels brief. Clearance Ahead

Effective Use of Text Label

Overheight vehicles take another route around restricted clearance.

Ineffective Use of Text Label

Use initial capital letters

when the label is not part

of the symbol.

Avoid using italics

to emphasize words.

The space between lines should be

at least 1/30 the line length.

Make the type >0.27 degrees

visual angle.

Use a clear and

simple font.

Keep text labels brief.

Figure 3-4. Schematic Examples of Text Labels 

 3-8
Discussion: Reference 1 studied the effect of character width and spacing on type legibility of warning labels. 

Pairwise comparisons were performed for every width and spacing combination. Results indicated that a reduction 

in character width had a more detrimental effect on legibility than inter-character separation. In addition, the study 

suggested that as character size increases, spacing may be decreased without a loss in readability. 

Reference 2 suggests that presenting text labels in addition to an icon is beneficial when the icon is not obvious or if

it is being presented for the first time. This reference provides several suggestions for successfully using text labels 

(see the “Design Guidelines” on the previous page). 

Research indicates that presenting an icon and a text label can increase comprehension and therefore overall 

effectiveness. For example, a study comparing people's ability to navigate through a database using either pictorial 

icons, text labels, or a combination of the two discovered that subjects were able to reach the target much more 

quickly and with fewer steps in the icon-text combination condition (reference 3). Another study found similar 

results when examining the role of graphics in the selection of items from a menu. Specifically, the study found that

text plus graphics greatly reduced the number of errors in selecting the desired item (see reference 4). 

Design Issues: The use of text labels in icon design can lead to problems, however. First, text labels should be

brief, containing no more than two or three words. However, not all icon concepts are amenable to such a succinct 

label. If not carefully chosen, a text label may mislead the user and reduce comprehension. Second, text labels

reduce the universal nature of icons, as they necessarily reflect a specific language and/or culture. Third, text labels

require additional display space. Such space might be better used to increase the size and understandability of the 

icon. 

Older drivers generally have poorer visual acuity than do younger drivers. Thus, the design guidelines specified 

above assume that, all other factors being equal, design objectives for icon text that meet the legibility needs of older 

drivers will always meet the legibility needs of younger drivers. 

Cross References:

Composition of an Icon, p. 2-10; Determining the Appropriate Size of Icon Components, p. 3-6; Enhancing Icon

Interpretation with Text Labels, p. 5-2; Composition of Text Labels, p.5-4

References:

1. Young, S. I., Laughery, K. R., and Bell, A. (1992). Effects of two type density characteristics on the legibility of

print. Proceedings of the 32nd Annual Human Factors and Ergonomics Society, 905-909. 

2. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

3. Edigo, C., and Patterson, J. (1988). Pictures and category labels as navigational aids for catalog browsing. 

Human Factors in Computing Systems: CHI ‘88 Conference Proceedings, 127-132.

4. Muter, P., and Mayson, C. (1986). The role of graphics in item selection for menus. Behaviour and Information

Technology, 5(1), 89-95. 

 3-9
THE EFFECTS OF COLOR ON ICON LEGIBILITY

Introduction: Our perception of color is derived from variations in the wavelength or spectral composition of light. 

Color perception can be described in terms of three psychological dimensions: hue, saturation, and brightness. Hue

is related to the dominant wavelength of the stimulus; saturation is somewhat more loosely related to the spectral 

bandwidth of the stimulus; and brightness is related to the luminance of the stimulus. 

Design Guidelines 

• Any reasonably visible color may be used to create icons as long as guidelines for symbol height and contrast

are followed and population stereotypes are not ignored. However, highly saturated blue (i.e., approximately

450 nanometers) should be avoided. 

• If colored lines are shown against a colored background, the color contrast between the elements should be a 

minimum of 100 E (CIE Yu’v’) distances. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

where:

∆E (CIE Yu' v' = the color contrast metric

∆Y = difference in luminance between text ( symbology ) and background

Ym = the maximum luminance of text ( symbology ) or background

∆u' = difference between u' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

∆v' = difference between v' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

∆E (CIE Yu' v') = [( ) ] 155 ∆Y

Ym

2

+ (367 ∆u')

2 + (167 ∆v') 2

0.5

(7)

NOTE: The constants 155, 367, and 167 in equation 7 are empirically derived weights (reference 1).

where:

∆E (CIE Yu' v' = the color contrast metric

∆Y = difference in luminance between text ( symbology ) and background

Ym = the maximum luminance of text ( symbology ) or background

∆u' = difference between u' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

∆v' = difference between v' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

NOTE: The constants 155, 367, and 167 in equation 7 are empirically derived weights (reference 1).

∆E (CIE Yu' v') = [( ) ] 155 ∆Y

Ym

2

+ (367 ∆u')

2 + (167 ∆v') 2

0.5

(7)

where:

∆E (CIE Yu' v' = the color contrast metric

∆Y = difference in luminance between text ( symbology ) and background

Ym = the maximum luminance of text ( symbology ) or background

∆u' = difference between u' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

∆v' = difference between v' coordinates of text ( symbology )

and background (per the 1976 CIE UCS; see note below)

NOTE: The constants 155, 367, and 167 in equation 7 are empirically derived weights (reference 1).

∆E (CIE Yu' v') = [( ) ] 155 ∆Y

Ym

2

+ (367 ∆u')

2 + (167 ∆v') 2

0.5

(7)

Figure 3-5. Equation for Determining Color Contrast

NOTE: Reynolds 1 states, “The discriminability of pairs of colors depends on their differences in chrominance and

luminance. While an entirely satisfactory metric does not exist which combines these attributes into a

single assessment of total color difference, an estimate can be derived by calculating the weighted 

difference between the locations of the colors in the 1976 Commission International de l’Eclairage 

Uniform Chromaticity-Scale (CIE UCS L*u*v*).” 

“Note that this estimate should be used only to ensure discriminability of colors of relatively high

luminance. Severe nonlinearities in the UCS limit the usefulness of this metric for colors having 

small luminance differences. In addition, the specification of small color differences should be

treated with caution due to the inherent lack of color uniformity on most CRTs.” 

 3-10 
Discussion: Despite well-established differences in visual sensitivity as a function of color (wavelength), there is no

consistent, empirical evidence that color has a meaningful effect on legibility (references 1, 2, and 3), and, in 

principle, any reasonably visible color may be used as long as recommendations for symbol height and contrast are

adhered to. It is recommended that a highly saturated blue be avoided because the central fovea is relatively

insensitive to highly saturated blue (references 4 and 5); highly saturated blue has also been associated with

“disruptions in accommodation” (reference 6).

Reference 4 has provided a metric for determining symbol colors to maximize legibility for symbols of relatively 

high luminance. This metric, E (CIE Yu’v’), which is shown in the figure, is derived from the 1976 CIE UCS color

diagram (CIE UCS). Although the metric does not combine the different attributes of color into a single assessment 

of total color difference, it provides a useful estimate of color contrast. Reference 4 indicates that for legibility of

colored symbols on a colored background (with relatively high luminance conditions), the colors should differ by a 

minimum of 100 E (CIE Yu’v’) distances. If the formula is applied to figures and backgrounds that differ negligibly

in u’ and v’, this value corresponds to approximately 80 percent luminance contrast, which is rather high in

comparison with traditional contrast recommendations.

Design Issues: Although E (CIE Yu’v’) provides a seemingly adequate measure of color contrast, it is clear that

much more research is needed in this area before specific recommendations regarding color contrast can be made for

automotive applications. Reference 7 notes that different experimental tasks as well as different response measures 

need to be investigated. 

Color contrast is a sufficiently difficult concept when applied to fixed-color, fixed-background displays; it becomes 

more complex when applied to displays such as automotive head-up displays (HUDs). With HUDs, the background 

for the symbology is dynamic and can be almost any color; background luminance can range from a fraction of a fL

to 6,000 or more fLs, depending on conditions. In addition, the symbology is translucent, which means that both the 

background color and luminance combine with the symbology’s color and luminance in an additive fashion. Color 

contrast, therefore, is not a very meaningful parameter when applied to HUDs. 

It should be noted that, while color may have very little effect on icon legibility, it is extremely important for 

successful icon interpretation. Effective uses of color can help a driver to group information, code information, 

attract their attention more quickly, and facilitate interpretation via the use of population stereotypes. These issues 

and more are discussed in chapter 5. 

Cross References:

Enhancing Icon Interpretation with Color, p. 5-12

References:

1. Reynolds, H. N. (1971). The visual effects of exposure to electroluminescent lighting. Human Factors, 13(1),

29-40.

2. Post, D. L. (1985). Effects of color on CRT symbol legibility. Society for Information Display 1985 Digest, 

196-199. 

3. Christ, R. E. (1975). Review and analysis of color coding research for visual displays. Human Factors, 17(6),

542-570. 

4. American National Standards Institute. (1988). American national standard for human factors engineering of

visual display workstations. Santa Monica, CA: Human Factors and Ergonomics Society.

5. Murch, G. M. (1987). Visual perception basics. Society for Information Display Seminar Lecture Notes, 1, 2-1 - 

2-36. 

6. Donohoo, D. T., and Snyder, H. L. (1985). Accommodation during color contrast. Digest of the Society for 

Information Display, 200-203.

7. Decker, J. J., Pigion, R. D., and Snyder, H. L. (1987). A literature review and experimental plan for research on

the display of information on matrix-addressable displays. Blacksburg, VA: Human Engineering 

Laboratory, Virginia Polytechnic Institute and State University. 

 3-11 
 

CHAPTER 4: ICON RECOGNITION 

Level of Realism.........................................................................................................................4-2 

Level of Detail ............................................................................................................................4-4 

Perceptual Principles of Icon Design..........................................................................................4-6 

Flash Rate....................................................................................................................................4-8 

Design of Prohibition Symbols.................................................................................................4-10 

Driver Acceptance of General versus Specific Icons ...............................................................4-12 

 4-1
 

LEVEL OF REALISM 

Introduction: Level of realism refers to the relationship between the portrayed object or concept and the graphic 

means used to represent that object or concept. The graphic realism of an icon can have an impact on 

comprehension. Recognition can be facilitated for some icons by adding small details, while others are improved by

a reduction in detail or by emphasizing important features. Only details that increase symbol recognition and

comprehension should be included. Details that detract from recognition and comprehension should be omitted.

Design Guidelines 

• For general or abstract concepts, less detailed symbols such as caricatures or silhouettes are most appropriate. 

• When several symbols have the same general shape or profile, detail is necessary to make them distinct from

one another. In this case, they may be best portrayed using a simplified drawing. 

• For small, familiar symbols with a distinct profile, use an outline. However, when the symbol is too thin to be

recognized in this format, a silhouette is preferred.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Example Level of Realism Design Style When to Use 

Simplified 

drawing 

Simplified drawing

with distinct interior

details 

For presenting complex symbols with

small significant parts, especially when 

objects have similar profiles (e.g.,

mechanical or electrical devices) 

Caricature Exaggeration of

crucial details 

For presenting symbols that have a 

small, crucial feature or for simplifying 

complex details 

Outline Outline with only 

prominent details 

For presenting small symbols that 

represent a familiar object with a distinct 

profile

Silhouette Shape filled with

solid color 

contrasting with

background

For presenting symbols that are too thin 

to show in outline format and for 

symbols that have a very distinct profile

and do not require detail for recognition

Figure 4-1. Five Levels of Realism 

 4-2
 

Discussion: Reference 1 discusses five different levels of realism that can be used: photographic realism,

simplified drawing, caricature, outline, or silhouette. Each of these styles has its place, where one may work better 

than another for conveying particular types of information. In the driving context, the more detailed styles, such as 

photographic and simplified drawings, are the least practical. The amount of information they attempt to display

makes them less recognizable in the sizes necessary for display. The silhouette style is the simplest of the five styles 

and is the most common type used in road signs. It is likely that this style will also be the most effective for use in

in-vehicle displays. 

Design Issues: When icons are being designed as a set, it is important that the same level of detail or realism be

chosen to portray the entire set. When this is not possible, the designer should choose both a primary style and an

alternate that is most similar (i.e., caricature and outline). This will help to not only increase the ease with which 

they are recognized but to help the user see them as a set of related icons. 

Cross References:

Level of Detail, p. 4-4; Identifying Icons as Part of a Group, p. 5-8 

References:

1. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

 4-3
 

LEVEL OF DETAIL

Introduction: Level of detail refers to the amount of detail necessary for recognition of a symbol. Only those 

details that contribute to the meaning of the symbol should be included, while those that distract from the true goals 

of recognition and comprehension should be omitted. A significant detail refers to a symbol element that would

reduce icon recognition and comprehension if removed. 

Design Guidelines 

• Design symbols on a 20 x 20 unit grid, making sure that no significant detail is smaller in size than 1 square 

unit (references 1 and 2). 

• Lines and other continuous aspects of the symbol do not need to span one grid square. 

• Significant details within a symbol should subtend, at a minimum, 3 degrees of visual angle (reference 3). 

• Line thickness for a significant detail should subtend, at a minimum, 2 degrees of visual angle (reference 3). 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Determine the appropriate level

of realism (e.g., silhouette).

No significant detail

should be smaller in

size than 1 square unit.

Design symbols on

a 20 x 20-unit grid.

Determine the appropriate level

of realism (e.g., silhouette).

No significant detail

should be smaller in

size than 1 square unit.

Design symbols on

a 20 x 20-unit grid.

Determine the appropriate level

of realism (e.g., silhouette).

No significant detail

should be smaller in

size than 1 square unit.

Design symbols on

a 20 x 20-unit grid.

Figure 4-2. Example of Appropriate Level of Detail 

 4-4
 

Discussion: Icons should be designed with the appropriate level of detail. Including details that are necessary for 

discriminability can make objects much easier to recognize. However, including excessive amounts of detail simply 

creates clutter and can contribute to driver distraction. Therefore, care should be taken to omit any unnecessary

details from the design. 

To ensure that the level of detail is appropriate, references 1 and 2 suggest that the design of symbols should take 

place on a 20 x 20-unit grid; significant details should be no smaller than one square unit. This simple method can 

help designers adjust the level of detail of a symbol so that it is less likely to distract the driver or clutter the display. 

Design Issues: There are several instances in which it may be necessary to increase the size of significant details 

within an icon: (1) when an icon is particularly important, such as in the case of warnings of imminent danger; 

(2) when icons suffer from unavoidable design deficiencies, such as poor color combinations, lack of adequate

illumination, or excessive complexity; and (3) when it is important that the icon be noticed against a visually 

complex background. 

Cross References:

Determining the Appropriate Size of Icon Components, p. 3-6; Level of Realism, p. 4-2 

References:

1. International Organization for Standardization (ISO) 7001. (1990). Public information symbols. Geneva, 

Switzerland: ISO. 

2. AS 2342. (1992). Development, testing, and implementation of information and safety symbols and symbolic 

signs. Sydney, Australia: Standards Australia. 

3. ISO/TR 7239. (1984). Development and principles for application of public information symbols. Geneva, 

Switzerland: ISO. 

 4-5
 

PERCEPTUAL PRINCIPLES OF ICON DESIGN

Introduction: Perceptual principles of icon design refer to design recommendations based solely on the visual

characteristics of the icon without reference to its intended function or meaning (see also references 1 and 2). 

Design Guidelines 

Icon Design Parameter Recommendation Do This... ...Not This 

Figure/ground relationship Emphasize a clear, stable, and

solid relationship between the 

elements of the symbol and its 

background

Figure edges Relatively solid shapes are 

better than thin or dotted-line 

edges unless the element in 

question depicts action or

movement

Closure Use closed figures without 

discontinuous lines, outlines, 

or disjointed elements that can 

result in a fragmented figure 

Simplicity Icons should be simple with

only the necessary detail

included; removal of these 

details should result in low 

recognition

Unity All parts of the symbol should 

be enclosed within a single 

boundary

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 4-3. Perpetual Principles of Icon Design 

 4-6
 

Discussion: Many of the perceptual theories about how we decode and comprehend symbols have come from the 

ideas and experiments that were completed by such Gestalt psychologists as Kohler, Wertheimer, and Koffka. They

were the first to discover that the determinants of shape and form are the figures in the visual field, which in turn are 

characterized by their contour (i.e., outline or boundary). This delineation of one part of the visual field from

another is called the “figure/ground” phenomenon. The Gestalt psychologists also derived many of the principles 

that comprise the concept of “figural goodness,” whereby the perceptual process of decoding incoming stimuli is

enhanced by the inherent clarity and stability of the form (reference 4). 

Easterby (references 2, 3, and 4) has conducted multiple studies that examine the figural aspects of symbols (e.g., 

the lines, curves, and graphics that make up a symbol) and using the principles of “figural goodness” to determine 

how they affect perception, recognition, understanding, and learning. He argues that the structural properties of a 

symbol are important determinates of its perceptibility and that they provide the contextual cues that define the 

meaning of a symbol (reference 1). These structural properties include aspects such as continuity, closure,

symmetry, simplicity, and unity (reference 2). 

Cross References: 

Composition of an Icon, p. 2-10; Design of Prohibition Symbols, p. 4-10

References: 

1. Barnard, P., and Marcel, T. (1984). Representation and understanding in the use of symbols and pictograms. In

R. Easterby and H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed 

material (pp. 37-75). New York: J. Wiley & Sons.

2. Easterby, R. S. (1970). The perception of symbols for machine displays. Ergonomics, 13(1), 149-158. 

3. Easterby, R. S. (1969). The grammar of symbols. Print, 13, 6. 

4. Easterby, R. S. (1967). Perceptual organization in static displays for man-machine systems. Ergonomics, 10(1),

193-205. 

 4-7
 

FLASH RATE

Introduction: Flash rate refers to the rate at which a signal alternates between an illuminated and a non-illuminated

state. References 1 and 2 provide several recommendations for the use of flashing signals. 

Design Guidelines 

• Flashing lights or icons should be reserved only for emergencies, because they have the potential to distract 

the driver. 

• Flash rates should be 3-10 per second (although 4 is best) with equal light/dark intervals. 

• Flash duration should be at least 0.05 second. 

• Only one signal should flash at a time. 

• The background should be steady when using flashing signals. 

• Flash rates should not be used as a visual coding method as only 2 levels can be discriminated on an absolute

basis under optimum conditions. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Appropriate Use of Flashing Icon

Inappropriate Use of Flashing Icon

Flashing signals should be reserved

for emergency situations for which

the driver’s immediate attention is

necessary (e.g., vehicle safety and 

warning information).

Use static signals to convey information that the driver does not

need immediately (e.g., motorist

services information).

Appropriate Use of Flashing Icon

Inappropriate Use of Flashing Icon

Flashing signals should be reserved

for emergency situations for which

the driver’s immediate attention is

necessary (e.g., vehicle safety and 

warning information).

Use static signals to convey information that the driver does not

need immediately (e.g., motorist

services information).

Appropriate Use of Flashing Icon

Inappropriate Use of Flashing Icon

Flashing signals should be reserved

for emergency situations for which

the driver’s immediate attention is

necessary (e.g., vehicle safety and 

warning information).

Use static signals to convey information that the driver does not

need immediately (e.g., motorist

services information).

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Figure 4-4. Schematic Examples of the Appropriate and Inappropriate Use of Flashing Icons

 4-8
 

Discussion: According to reference 2, flash rates should be well below that at which a flashing light appears to be a 

steady light, which is approximately 30 times per second. Reference 1 recommends rates of about 3 to 10 per 

second, but states that 4 per second would be best. And reference 3 provides the same recommendation, adding that

the flash duration should be at least 0.05 second. 

Design Issues: Flashing signals are an excellent means for attracting the attention of the driver; therefore, it is 

extremely important that they be used only to signal emergency situations. Their ability to quickly gain and divert 

the driver’s attention makes them an unsafe means for presenting noncritical or status information. It is also 

important to understand how the overuse of flashing signals can actually produce the opposite effect that may be 

desired. As more than one flashing light is introduced into the environment, the amount of time it takes a driver to

react actually increases. Reference 4 found that, if even one irrelevant background light was flashing, reaction time 

would be greater than for a steady signal. Therefore, it is recommended that backgrounds remain steady when using 

a flashing signal and that only one signal flash on a display at a time. 

Cross References:

Ways to Use Icons, p. 2-6; Conveying Urgency with Icons, p. 5-14

References:

1. Heglin, H. J. (1973). NAVSHIPS display illumination design guide: II. Human factors (NELC/TD223). San 

Diego, CA: Naval Electronics Laboratory Center. 

2. McCormick, E. J., and Sanders, M. S. (1982). Human factors in engineering and design (5th ed.) New York:

McGraw-Hill. 

3. Woodson, W. E., and Conover, D. W. (1964). Human engineering guide for equipment designers (2nd ed.)

Berkeley, CA: University of California Press. 

4. Crawford, A. (1963). Perception of light signals: The effects of mixing flashing and steady irrelevant lights. 

Ergonomics, 6, 287-294. 

 4-9
DESIGN OF PROHIBITION SYMBOLS 

Introduction: Design of prohibition symbols refers to icons that present a specific action and communicate that the 

action should be avoided. Prohibition should be indicated by overlaying the action symbol with a red circle and 45° 

slash (top left to bottom right) or cross. 

Design Guidelines 

• Care should be taken not to obscure small details of the symbol with the slash or cross. When necessary, the 

symbol’s placement or orientation may need to be changed. Modification of the slash may also be necessary 

to ensure the display of all important features. See the table below for alternative methods for indicating 

prohibition. 

• Use full-length, solid slashes rather than partial or transparent ones. Slashes that appear in front of or behind

the pictorial are preferred. 

• Use a standard circle and 30°–60° slash to indicate prohibition. The circle and slash should be colored red for 

saliency. 

• Use pictorials that do not contain too many small details small details are likely to be obscured by the circle 

or slash, making the pictorial ambiguous. 

• Avoid using pictorials that show a negative consequence of an action. With the slash removed, the pictorial

should portray a positive course of action.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Method Example 

Change slash angle to 30°–60°. 

Reverse direction of the slash. 

Reverse direction of the symbol. 

Displace slash to either side of center. 

Use a cross rather than a slash. 

Figure 4-5. Examples of Alternative Methods for Indicating Prohibition 

 4-10 
Discussion: A glance legibility study (reference 1) asked participants to match an image they had been shown for 

either 1/10 s or 1/25 s to various traffic symbols on an answer sheet. Performance was much worse for those 

symbols with slashes either in front of or behind the pictorial than for those symbols with either a partial slash or no

slash. It was concluded that the conventional circle and slash obscured portions of the pictorial and increased the 

overall complexity of the pictorial. Several recent studies, however, have found that people prefer symbols with the 

slash either in front of or behind the pictorial (references 1 and 2) and view these symbols as being more effective. 

Care must be taken when determining the placement of the slash, because a larger symbol may obscure a posterior 

slash, concealing that the symbol conveys a prohibition. Reference 3 hypothesizes that this may be due to viewers’ 

familiarity with this format, since most symbols are currently being designed this way, or it could be due to the 

Gestalt principles of good figures. 

The effectiveness of prohibition symbols is lowered by ambiguity, complexity, and confusability (reference 3). 

Ambiguity refers to symbols on which the slash has obscured some detail of the pictorial, making it possible for the 

symbol to have several different meanings. Complexity refers to symbols that attempt to include too much

information (i.e., both an action and its consequence). Confusability refers to symbols that have unfamiliar or

unusual features. 

Design Issues: There are some ambiguities and inconsistencies across the literature on this topic. A red circle and

slash is recommended by several standards documents (see references 4 and 5) for warning pictorial design. This

design approach is also consistent with the perceptual principles discussed on page 4-6. However, research suggests

that this format may actually obscure the symbol, making the icon much harder to recognize (references 1, 2, and 3). 

Reference 2 indicates that careful consideration of the placement of the pictorial is necessary. Potential solutions to 

the problem of obscuring the symbol include changing the orientation of the pictorial, modifying the pictorial so that

all important features are displayed or, in some cases, rethinking the overall concept behind the symbol and 

redesigning it completely. Reference 6 presents designers with several alternative methods for indicating 

prohibition when the standard 45-degree top-left-to-bottom-right slash covers too much of the symbol. 

Cross References:

Composition of an Icon, p. 2-10; Perceptual Principles of Icon Design, p. 4-6 

References:

1. Dewar, R. E. (1976). The slash obscures the symbol on prohibitive traffic signs. Human Factors, 18(4), 253-

258. 

2. Glover, B. L., Magurno, A. B., Murray, L. A., and Wogalter, M. S. (1996). Pictorial negation: Preferences for 

different circle-slash variations. Proceedings of the Human Factors and Ergonomics Society 40th Annual

Meeting, 910-914. 

3. Murray, L. A., Magurno, A. B., Glover, B. L., and Wogalter, M. S. (1997). Prohibitive pictorials: Evaluations 

of different circle-slash negation symbols. International Journal of Industrial Ergonomics, 22, 473-482. 

4. American National Standards Institute. (1991). American national standard for environmental and facility 

safety signs: Z535.2. Washington, DC: Author. 

5. ISO 3864. (1984). International standard for safety colours and safety signs. Geneva, Switzerland: ISO. 

6. AS 2342. (1992). Development, testing, and implementation of information and safety symbols and symbolic 

signs. Sydney, Australia: Standards Australia. 

 4-11 
DRIVER ACCEPTANCE OF GENERAL VERSUS SPECIFIC ICONS

Introduction: General vs. specific icons refers to the degree to which an icon provides information about a general

class of in-vehicle messages vs. providing detail about the specific nature of an in-vehicle message. General icons

are defined as icons that provide the driver with information about a broad driving situation or class of conditions

without specifying detailed information about the situation or conditions. For example, a general icon for the 

message “crash warning” would indicate that a crash is imminent, but would not convey information regarding the 

precise nature of the projected crash (e.g., side, front, or rear crash). Specific icons are defined as icons that do

provide more detailed information about a driving situation or conditions. For example, a family of specific crash 

warning icons could be used, with each icon describing the specific nature of the projected crash (e.g., side, front, or

rear crash). The table below shows some examples of general and specific icons for key in-vehicle message

categories.

Design Guidelines 

• To minimize driver memory requirements and system complexity, general icons should be used as long as 

they do not negatively impact driver acceptance or performance. Well-designed general icons will be

acceptable to most drivers under most driving circumstances 

• The exception to this seems to be safety-related messages (e.g., collision avoidance icons). For safety-related

messages, specific icons will provide higher levels of driver acceptance than do general icons. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

MESSAGE GENERAL ICONS SPECIFIC ICONS

Trip navigation: Reduce speed 

Trip navigation: Lane blocked 

Trip navigation: Road closed 

Trip navigation: Emergency vehicle 

Trip navigation: Route guidance 

Collision avoidance system: Crash warning 

Vehicle condition monitoring: Urgent mechanical problem 

Vehicle condition monitoring: Vehicle maintenance required 

ATIS (motorist services): Lodging 

ATIS (motorist services): Food 

ATIS (motorist services): Gas 

ATIS (motorist services): Water recreation 

 

 

 

Figure 4-6. Examples of General and Specific Icons for Key In-Vehicle Message Categories

 4-12 
Discussion: Currently, the typical icon development approach entails the assignment of a specific icon to each 

driver message. For example, specific icons are used to depict low fuel conditions, weather conditions, and motorist 

services. The number of specific icons presented to drivers increases with the proliferation of In-Vehicle 

Information System (IVIS) devices. Unfortunately, this will place greater cognitive and memory burdens on the

driver and may eliminate the advantages associated with using visual icons in the first place. In particular, workingand long-term memory capacities are quite limited (see reference 1), especially when retrieval strategies (chunking, 

rehearsal, auditory redundancy) strategies are not available (reference 2). 

An alternative approach to using many specific icons to communicate individual messages is to use general icons to

convey information about a class of conditions. Such an approach will work best in situations where the driver may 

not need detailed or specific information to understand the message sufficiently to take the appropriate driving 

action(s). The key advantage of general icons over specific icons is a reduction in the total number of icons that

would be used within the in-vehicle environment. 

Reference 3 investigated driver perceptions of the accuracy and acceptability of generic vs. specific icons for a range 

of in-vehicle message types. The effects of icon type (general vs. specific) were strongly mediated by the scenario 

descriptions given to subjects. Overall general icons were selected as the most accurate when subjects were

presented with a general description of a particular driving scenario, and specific icons were selected as the most 

accurate when subjects were presented with a specific description of a particular scenario. However, for two 

message categories—collision avoidance and water recreation—specific icons were selected as the most accurate 

icons regardless of the scenario description. For the collision avoidance icons at least, this suggests that specific 

icons are desired where safety is an issue, perhaps because drivers want to have as much information as is available.

These general findings, however, should be considered in light of results from the study relating to the acceptability 

of general vs. specific icons. While the perceived accuracy of icons varied as a function of the scenario described to

the subjects. High levels of acceptability were obtained for both the general and specific icons, regardless of 

scenario description. Specifically, the general icons resulted in 80 percent or higher levels of acceptance in 23 out of 

23 messages in the general scenario description condition and in 20 out of 23 messages in the specific scenario

description condition (exceptions were one of the three emergency vehicle messages and both vehicle maintenance 

messages). Therefore, it seems very clear that general icons are capable of meeting driver expectations and 

preferences for a broad range of IVIS messages. 

Design Issues: Reference 3 only investigated driver acceptance of general vs. specific icons. Driver behavior and 

performance issues for the “general vs. specific” question remain to be investigated. 

References: 

1. Miller, G. A. (1956). The magical number seven plus or minus two: Some limits on our capacity for processing

information. Psychological Review, 63, 81-97.

2. Wickens, C. D. (1992). Engineering psychology and human performance (2nd Ed.). New York: Harper-Collins 

Publishers, Inc. 

3. Campbell, J. L., Richman, J. B., Nakata, A., Simsek, O., and Schmidt, K. (2002). In-vehicle display icons and

other information elements. Task E, Experiment 6. General versus specific icons: Implications for driver 

acceptance of IVIS messages (Final Report). Seattle, WA: Battelle Human Factors Transportation Center. 

 4-13 
 

CHAPTER 5: ICON INTERPRETATION 

Enhancing Icon Interpretation with Text Labels .........................................................................5-2 

Composition of Text Labels.........................................................................................................5-4 

Conveying the Effect of Actions with Icons................................................................................5-6 

Identifying Icons as Part of a Group............................................................................................5-8

Conveying System Status with Icons.........................................................................................5-10

Enhancing Icon Interpretation with Color .................................................................................5-12 

Conveying Urgency with Icons .................................................................................................5-14 

Enhancing Icon Interpretation with Shape.................................................................................5-16 

 5-1
 

ENHANCING ICON INTERPRETATION WITH TEXT LABELS 

Introduction: Text labels refers to the use of text descriptions to enhance the interpretation of icons. Many icons 

are not immediately understood by drivers and text labels can facilitate the learning process. 

Design Guidelines 

Text labels should be considered when: 

• Icons are abstract and have no conventional or broadly understood meaning.

• The icon represents a message that is particularly important or warns of a particularly hazardous situation.

• The driver can safely spend one to three seconds interpreting the icon. 

• The task is complex.

Keep text labels concise (two to three words) and use them sparingly. Text labels reduce the space available for 

the icon, making them less interpretable. 

Icon Icon with Text Label Added Benefit of Label 

The synergy of the icon and embedded text label 

quantifies the degree of hazard and clarifies a 

potentially ambiguous image.

Text label embedded in the icon clarifies an ambiguous 

icon by clearly identifying the type of vehicle.

Text label beneath the icon clarifies the meaning of a 

complex combination of icons.

Text label provided on demand through a cursor 

selection clarifies icon meaning for those unfamiliar 

with the system without cluttering the display for more 

expert users.

Semitransparent labels provide a redundant indicator of 

system status.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

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Trail Parking

Congestion

Ahead

Figure 5-1. Examples of Icons that Benefit from Text Labels

 5-2
 

Discussion: Many icons may be misinterpreted because they have no commonly understood meaning and must be 

learned by the users (reference 1). This is particularly true of abstract icons that have no intuitive link to the 

message they try to communicate. The appropriate use of text labels can alleviate this problem. In fact, icons paired 

with text labels have been found to enhance performance, compared to icons alone, and enhance perceptions of

usefulness, compared to text alone (references 2 and 3). Text labels can enhance interpretation by improving

learning, identifying an appropriate action, and emphasizing hazards or important information. Even short text 

labels can help users learn icon meanings, which can be flawlessly recalled months after the initial exposure to the 

icon (reference 4). Text labels can also clarify a message and guide users to correct actions that might otherwise be

obscured if the message were portrayed with only an icon or text (reference 5). Text labels also help clarify the 

uncertainty associated with color codes and shapes used to convey urgency. Used appropriately, text labels can

address several problems of icon interpretation and provide benefits beyond those available with either text or icons

alone. 

Design Issues: Including a text label may not be possible without reducing the size of the icon and compromising 

icon legibility. With this design tradeoff in mind, three placement strategies can be considered to accommodate a 

text label. Most simply, the icon label can be placed at the bottom or top of the icon. This alternative consumes 

valuable space and may reduce the icon size, but it provides a clear identification of the icon. The label can also be 

devised so that it appears only on command, such as when it becomes activated by the cursor. This strategy does not

impinge on display space, but novice users may not be aware that the icon label can be accessed through the cursor. 

More expert users may not need or want this feature, so allowing users to turn off the text would support novice 

users until they no longer need the icon definitions. Because this strategy requires cursor movement, it is not 

feasible for those icons that will be displayed while a vehicle is in motion. The label can also be directly 

superimposed on the icon itself. This strategy does not require additional display space, but it may interfere with 

icon legibility because the label may occlude critical elements of the icon. Making the lettering semitransparent will 

reduce the occlusion of the icon, but it will also reduce the legibility of the text. Reference 6 discusses several 

detailed strategies for combining text and graphical information effectively. 

Cross References:

Designing Effective Text Labels, p. 3-8; Composition of Text Labels, p. 5-4; Conveying Urgency with Icons, p. 5-14

References:

1. Baber, C., and Wankling, J. (1992). An experimental comparison of text and symbols for in-car reconfigurable

displays. Applied Ergonomics, 23(4), 255-262. 

2. Wiedenbeck, S. (1999). The use of icons and labels in an end user application program: An empirical study of 

learning and retention. Behaviour & Information Technology, 18(2), 68-82.

3. Ramakrishnan, A. S., Cranston, R. L., Rosiles, A., Wagner, D., and Mital, A. (1999). Study of symbols coding

in airway facilities. International Journal of Industrial Ergonomics, 25(1), 39-50. 

4. Wogalter, M. S., and Sojourner, R. J. (1997). Comprehension and retention of safety pictorials. Ergonomics, 

40(5), 532-542.

5. Edigo, C., and Patterson, J. (1988). Pictures and category labels as navigational aids for catalog browsing. 

Human Factors in Computing Systems: CHI ‘88 Conference Proceedings, 127-132.

6. Tufte, E. R. (1983). The visual display of quantitative information. Cheshire, CT: Graphics Press. 

 5-3
 

COMPOSITION OF TEXT LABELS

Introduction: The content of text labels can affect the comprehension and interpretation of an icon’s text label. 

Words should be chosen carefully to increase clarity and take into account the vocabulary level of potential users. 

Design Guidelines 

• Use explicit icon descriptions. Explicit text labels improve comprehension (references 1 and 2) and are

perceived as conveying a more salient notification than non-explicit labels (references 2–4). In addition,

precise descriptions allow the driver to judge when or where a situation will occur and thus aid in response 

preparation. 

• Use nontechnical, common vocabulary (reference 5). Users will not know how to respond to a warning if 

they do not understand the text verbiage. 

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Table 5-1. Examples of Text Label Composition 

Vague Explicit Technical Nontechnical 

Bump Bump 100 Feet Right Turn Prohibited No Right Turn

Trucks Entering Highway Trucks Entering Right Alternator Malfunction Charging System Failure 

Congestion Congestion 2 Miles Reduce Velocity Reduce Speed 

 5-4
 

Discussion: Research indicates that warning text explicitness and severity has an effect on the perceived level of

hazard of product warning labels (references 1, 2, 3, and 4). For example, reference 2 examined the explicitness of 

warning labels on infant car seats. Subjects rated their perceived hazard, likelihood and severity of possible injury, 

and the intent to act cautiously. Results indicate that explicit warning labels increase the perception of possible 

hazards and injuries as well as ratings of cautious intent. 

Reference 5 evaluated the comprehension of product warning labels, specifically the difference between 

“flammable” and “combustible.” The study found that very few respondents knew the difference between the two 

terms, and most perceived the incorrect term as more hazardous. Similarly, terms used to describe driving situations 

may be misunderstood or ignored by drivers who do not comprehend the vocabulary used. 

Design Issues: When selecting icon text wording, using more explicit labels describing severe consequences can

increase warning compliance. However, to be effective, these descriptions must consider the users’ vocabulary

level. A compromise between terminology simplicity and precision must be made to increase comprehension. 

For example, an icon alerting the driver to a malfunction of the vehicle's alternator can be described in a number of 

ways. A message such as “Engine Problem” may not be adequately explicit, while “Alternator Failure” may be 

overly precise and not understood by users who are not familiar with engine terminology. A compromise such as 

“Charging System Failure” may be sufficient. 

Under elevated stress conditions, simple instructions should be provided to reduce cognitive burden and decrease 

reaction time. 

Cross References:

Designing Effective Text Labels, p. 3-8; Enhancing Icon Interpretation with Text Labels, p. 5-2; Enhancing Icon

Interpretation with Color, p. 5-12; Conveying Urgency with Icons, p. 5-14

References:

1. Laughery, K. R., Sr., and Stanush, J. A. (1989). Effects of warning explicitness on product perceptions. 

Proceedings of the Human Factors Society 33rd Annual Meeting, 431-435.

2. Trommelen, M. (1997). Effectiveness of explicit warnings. Safety Science, 25(1-3), 79-88.

3. Laughery, K. R., Sr., Rowe-Halbert, A. L., Young, S. L., Vaubel, K. P., and Laux, L. F. (1991). Effects of 

explicitness in conveying severity information in product warnings. Proceedings of the Human Factors 

Society 35th Annual Meeting, 481-485.

4. Laughery, K. R., Sr., Vaubel, K. P., Young, S. L., Brelsford, J. W., Jr., and Rowe, A. L. (1993). Explicitness of

consequence information in warnings. Safety Science, 16, 597-613. 

5. Main, B. W., Frantz, J. P., and Rhoads, T. P. (1993, July). Do consumers understand the difference between 

“flammable” and “combustible?” Ergonomics in Design, 1(3), 14-17.

 5-5
 

CONVEYING THE EFFECT OF ACTIONS WITH ICONS

Introduction: Conveying the effect of actions with icons refers to the ability of an icon to help the driver anticipate 

the effect of selecting a particular system function or option.

Design Guidelines 

• Show consequences of action with arrows, speed lines, or the ghosting of images. 

• Use sequence of images to convey simple transformations.

• Consider animated icons for predrive applications to show complex multistep consequences. 

Because of the distracting nature of animated icons, they should be used only rarely and with great caution. 

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Icon Characteristic Examples 

Arrows 

Speed Lines 

Sequencing of Images 

Ghosting 

Figure 5-2. Schematic Examples of Conveying Action 

 5-6
 

Discussion: Drivers may act upon icons that are used to identify system functions or options by pressing buttons or

selecting menu items. Because these actions will change system modes or select a function, it is important that the 

icon show the driver the consequence of the action. The icon should show the “effect” or action that will occur 

when the control is actuated. When a symbol conveys action, it is important that the resulting action is the 

mechanism displayed. Actions can be displayed several ways: using arrows, speed lines, ghosting, or sequencing 

and animation (reference 1). Arrows indicate direction of change or movement, as in increasing volume or panning 

over an electronic map. Speed lines indicate activation, as in alarm or when sensors are enabled. Ghosting of an

image shows an ordered sequence of states that will occur when the control is activated (reference 2) by using 

similar pictures with increasing levels of contrast—for example, the sequential position of a car on a route. 

Sequencing of images performs a similar function. By showing several images with connecting arrows, the

consequence of an action can be shown, as in replying to an e-mail message (reference 3). Sequencing of images 

can be achieved with multiple small images shown at the same time or in animated sequences that show an icon

changing over time. Each of these mechanisms for conveying action can help drivers understand the consequence of

actions. 

For these mechanisms to be successful, the icon must provide a context to highlight the relevant change. Some

important elements of context include position, orientation, and similarities in content. Regarding position, drivers 

will generally perceive the images on the right as occurring after the ones on the left. Ghosted images can also be

overlapped to show progression, with the previous states positioned behind the more recent. Icon orientation and

similarities in content can also provide a context for showing change. By retaining key features or orientation of the

icon in each of the multiple images, drivers will be able to identify how the elements of a sequence relate to each

other. 

Design Issues: Animated icons can be a very effective mechanism for describing actions, but they are not 

appropriate for icons displayed while the vehicle is in motion. A constantly changing icon will distract driver 

attention from the roadway (reference 4). 

References:

1. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: J.

Wiley & Sons. 

2. Tufte, E. E. (1997). Visual explanations: Images and quantities, evidence and narrative. Cheshire, CT: 

Graphics Press.

3. Dreyfuss, H. (1966). Case study: Symbols for industrial use. In G. Kepes (Ed.), Sign, image, symbol 

(pp. 126-133). New York: Braziller. 

4. Theeuwes, J., Kramer, A. F., Hahn, S., and Irwin, D. E. (1998). Our eyes do not always go where we want them

to go: Capture of the eyes by new objects. Psychological Science, 9(5), 379-385. 

 5-7
 

IDENTIFYING ICONS AS PART OF A GROUP

Introduction: Grouping icons facilitates their identification as a set of related messages or similar commands. 

Grouping provides the driver with cues regarding system functionality and aids icon comprehension. Grouping can

be accomplished using position, design, and labeling. 

Design Guidelines 

• Group icons based on the tasks that the user performs, rather than the architecture of the system. 

• Put related icons close together, especially those that are almost the same and those that are opposite. 

• If an icon fits into more than one group, duplicate it for each group.

• As a last resort, label groups of icons or individual icons. 

• Put groups into separate boxes or windows. 

• Put borders or extra space between groups of icons. 

• Use a common color for background or icon elements to distinguish groups. 

• Within a group of icons, use similar style, level of realism, and level of detail. 

• Combine, transform, and include elements from other icons in the same group. 

Description Example 

Common boundary identifies a group of icons as 

conveying warning information. 

Icons identified by a common level of detail and 

realism.

Icons identified by a common style. 

Icons grouped by border, background, color, and

style. 

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Figure 5-3. Schematic Examples of Ways to Identify Icons as Part of a Group

 5-8
 

Discussion: The context in which an icon is viewed provides a powerful influence on interpretation. Context can 

make an ambiguous icon meaningful. Identifying an icon as part of a group provides a context that can enhance 

icon interpretation, so it should be used when possible. Icons can be associated with a group by their physical

location or proximity, icon style, level of detail, common borders or shapes, or by the use of color. These icon

characteristics can be used to group icons according to three important criteria. The first grouping criterion is 

relative urgency or importance. This criterion has been used for many years to group highway signs. Highly urgent

signs have a distinct shape and color as shown by the examples that show warning information. The second

criterion is to identify icons based on whether they invoke system functions or display status information. Icons that

can be used to invoke system functions should have common characteristics that suggest that they can be acted 

upon, such as a raised bezel suggesting a physical button that could be depressed. The third criterion that can be 

used to group icons is system function. These system functions should reflect driver needs, not system architecture 

(reference 1). 

Relationships between groups can be conveyed through the use of common and distinct pictorial elements. For 

example, the use of similar shapes, colors, or borders can make icons appear related. This type of relation can be

explained in terms of the Gestalt law of similarity, where there is a tendency for the visual system to group similar 

elements together as if they belong to each other. Organizing icons into groups according to their global features

(i.e., shape, size, color) has also been shown to aid in discrimination. In reference 2, selection and response times 

for three different sets of icons were compared: a set in which the icons differed by their global features, a set in

which the icons differed by their local features (i.e., lines and structures within the icon), and a word set. The results 

indicated that the global features of an icon elicited faster response times than local features. This phenomenon is

referred to as the “global superiority effect” (references 3 and 4). In addition, reference 5 examined the use of color 

in icon design and found that color may be most useful for dividing icons into related subgroups and facilitating

rapid identification.

Design Issues: Although labeling is suggested as a means for grouping icons (reference 6) and has been shown to

be helpful for increasing comprehension and overall effectiveness (references 7 and 8), it is important that it be used 

as a last resort in this particular application. The most important reason for this is that design space may be 

extremely limited. Text labels must be kept brief with no more than one or two words, and not all icon concepts

may be amenable to such a succinct label. If not carefully chosen, a text label may mislead the user and reduce 

comprehension.

Cross References:

Enhancing Icon Interpretation with Text Labels, p. 5-2; Conveying the Effect of Actions with Icons, p. 5-6;

Enhancing Icon Interpretation with Color, p. 5-12; Enhancing Icon Interpretation with Shape, p. 5-16

References:

1. Lee, J. D. (1997). A functional description of ATIS/CVO systems to accommodate driver needs and limits. In 

Y. I. Noy (Ed.), Ergonomics and safety of intelligent driver interfaces (pp. 63-84). Mahwah, NJ: 

Lawrence Erlbaum Associates. 

2. Arend, A., Muthig, K., and Wandmacher, J. (1987). Evidence for global superiority in menu selection by icons. 

Behaviour & Information Technology, 6, 411-426. 

3. Pomerantz, J. R. (1983). Global and local precedence: Selective attention in form and motion perceptions. 

Journal of Experimental Psychology: General, 112, 516-540. 

4. Wandmacher, J., and Arend, U. (1985). Superiority of global features in classification and matching. 

Psychological Research, 47, 143-151. 

5. Davidoff, J. (1988). The colour of colour in visual displays. In D. J. Osborne (Ed.), International reviews of

ergonomics (pp. 21-42). London: Taylor and Francis. 

6. Horton, W. K. (1994). The icon book: Visual symbols for computer systems and documentation. New York: 

J. Wiley & Sons. 

7. Edigo, C., and Patterson, J. (1988). Pictures and category labels as navigational aids for catalog browsing. 

Human Factors in Computing Systems: CHI ‘88 Conference Proceedings, 127-132.

8. Muter, P., and Mayson, C. (1986). The role of graphics in item selection for menus. Behaviour & Information 

Technology, 5(1), 89-95. 

 5-9
 

CONVEYING SYSTEM STATUS WITH ICONS

Introduction: Conveying system status with icons refers to changing icon appearance to convey changes in the 

system state. Frequently this will represent a simple on/off or active/inactive status, but it can include more complex

multistate descriptions. 

Design Guidelines 

• Use a uniform decrease in contrast or a change of solid to dashed lines to convey on/off or active/inactive 

change. 

• Use an easily recognizable element and project changes upon it to convey system status that is described by

multiple categories. 

• Represent status changes associated with changes in magnitude by increasing the number or size of well 

differentiated icon elements, rather than changing color or contrast. 

• Consider using text or numbers to represent changes of magnitude or categories. 

Based Equally on Expert Judgment

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Description Examples 

On/off status indicated by decreased 

contrast and gray or dashed lines.

Lodging available Lodging unavailable 

Changes of categorical variables

represented by changes projected on an

easily recognizable element.

Diesel available next exit Gasoline available next exit 

Changes in magnitude represented by

increasing the number of welldifferentiated icon elements.

High speaker volume Low speaker volume

Changes in magnitude represented by

the addition of a numeric label.

Five percent grade Ten percent grade 

5 %

Figure 5-4. Examples of Conveying Status

 5-10 
 

Discussion: Icons can be used to convey many different types of information about system status. For the purpose

of icon design it is useful to describe this information in terms of urgency and information type. Information type

refers to three categories of information: binary, categorical, and magnitude. Binary state information describes

system state in terms of being on/off or active/inactive distinctions. Icons convey this information best through

global changes to the icon, such as a uniform change in contrast. Categorical information describes the availability 

of amenities or features of a system that are currently engaged. To convey this information, icons must provide a 

uniform context upon which changes can be made to indicate changes in the categorical information. For example, 

a “D” can be superimposed on a gas pump to indicate the availability of diesel gas. The gas pump icon provides the 

uniform context for the interpretation of the “D.” Magnitude information refers to continuous or discrete

information that can be ordered along a dimension such as small to large, low to high, or safe to dangerous 

(reference 1). To convey magnitude information, icons should increase the size or number of a distinct element of 

the icon. Numbers can be superimposed on the icon, particularly when precision is required. Color, angle, and

contrast have a very limited ability to convey magnitude information (references 2 and 3). 

Design Issues: For icons to convey highly urgent signals clearly, differentiating state changes is particularly

important. For example, a collision avoidance icon might indicate that the system is active and functioning

properly. The same icon might be used to indicate a collision situation. This state change requires a more salient

and recognizable indicator than an icon that shows whether the radio is on or off. To enhance the salience, the 

change should be accompanied by an auditory signal, the degree of change of contrast should be greater, and the 

color should emphasize the urgency of the signal.

Cross References:

Conveying the Effect of Actions with Icons, p. 5-6; Enhancing Icon Interpretation with Color, p. 5-12;

Conveying Urgency with Icons, p. 5-14; Augmenting Icons with Auditory Information, p. 6-2 

References:

1. Zhang, J. J. (1996). A representational analysis of relational information displays. International Journal of

Human-Computer Studies, 45(1), 59-74.

2. Zhang, J. J., and Norman, D. A. (1995). A representational analysis of numeration systems. Cognition, 57(3),

271-295. 

3. Tufte, E. R. (1983). The visual display of quantitative information. Cheshire, CT: Graphics Press. 

 5-11 
 

ENHANCING ICON INTERPRETATION WITH COLOR

Introduction: Enhancing icon interpretation with color refers to how color can highlight information and enhance 

drivers’ interpretation of icons; however, color can also confuse and mislead drivers if used incorrectly.

Design Guidelines 

• Use color coding only when well-established conventions exist, such as temperature, dangerous situations, 

and permissiveness. 

• Use red to indicate highly urgent messages, yellow to indicate cautionary information, and green to indicate 

normal operations or safe conditions. 

• For temperature, use red for hot and blue for cold. 

• Arbitrary codes using color to convey meaning are likely to induce errors. 

• Color, such as red, can be used to enhance the relative salience of icons. Therefore, color choices should be 

made with respect to the relationship between messages (relative urgency of messages) and the relationship

between messages and the background upon which they are presented.

• Small spots of intense saturated color can convey information effectively. This requires a conservative use of

these colors and the use of less saturated colors for backgrounds (reference 1).

• Use shades of gray, rather than color, for showing quantity (reference 2). 

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Explanation Example 

Red enhances the relative salience of this icon and the strong population stereotype

indicates a hazard. 

Yellow is often used for information such as caution or wait. 

Green is often used to indicate normal operations or to indicate permissible 

behavior. 

The small spots of intense color greatly enhance the effectiveness of this icon in

identifying heavy traffic. 

Figure 5-5. Schematic Examples of the Use of Color in Icons 

 5-12 
 

Discussion: The most common and consistent use of color for conveying information in the driving context is in 

traffic control devices. The use of green as permissive, amber or yellow for warning, and red for restrictive is 

almost universal. Red also has a powerful ability to convey urgency and hazard when used in warnings. Another 

important instance where color has come to hold a strong meaning is in the use of red for hot and blue for cold. 

These are two examples of “population stereotypes” or generally held expectations. When designing with color it is 

important to understand population stereotypes and conform to these expectations. Colors should not be used to

convey meaning when there is not a well-established stereotype. Drivers will confuse the meaning of arbitrary color 

codes. 

Beyond conveying specific meaning, color can also effectively highlight information and enhance interpretation of 

complex icons (references 1 and 2). Effective use of color in this role requires careful design that considers the use 

of color in relation to its context. Using color to highlight specific features or to enhance the salience of an icon

requires a relatively muted and conservative use of color elsewhere. If all icons are designed to be relatively salient

with the use of saturated colors, the resulting collection will have no highly salient icons. Similarly, highlighting a 

critical element of an icon with a saturated color requires that the other elements of the icon provide a background

that does not compete with the highlighted details. Color choices should be made with a clear sense for the 

importance of elements within the icon and priority or urgency across a set of icons. 

Design Issues: Color poses several problems for design. Some systems may not support color, so a monochrome

design may need to be created. Gray scale can substitute for color, with the intensity of the gray conveying the 

meaning of the color. For example, if red were replaced by dark gray or black, then yellow and green would be 

replaced by corresponding lighter shades of gray. In addition, nearly 10 percent of the Caucasian male population

and 4 percent of the non-Caucasian male population suffer from either color deficiencies or color blindness. The 

following color combinations should be avoided for these individuals: cyan and gray, yellow and light green, green

and brown, red and black. 

Cross References:

Ways to Use Icons, p. 2-6; Determining the Appropriate Contrast within an Icon, p. 3-4; The Effects of Color on

Icon Legibility, p. 3-10; Identifying Icons as Part of a Group, p. 5-8; Conveying Urgency with Icons, p. 5-14; 

Enhancing Icon Interpretation with Shape, p. 5-16

References:

1. Tufte, E. R. (1990). Envisioning information. Cheshire, CT: Graphics Press.

2. Tufte, E. R. (1983). The visual display of quantitative information. Cheshire, CT: Graphics Press. 

 5-13 
 

CONVEYING URGENCY WITH ICONS

Introduction: Conveying urgency with icons refers to adjusting icon characteristics so that they reflect the 

appropriate level of urgency of the situation. These adjustments enhance response speed and appropriateness. 

Design Guidelines 

To increase the perceived urgency of an icon:

• Increase font size of text labels to identify icons of greater urgency.

• Increase white space around label. 

• Use red lettering or red background. 

• Increase line weight of border.

• Use blinking or flashing to draw attention to icon. 

• Increase relative size of the high urgency icon. 

• Always position urgent warnings within 30 degrees of the operator’s normal line of sight.

• Pair with an auditory cue. 

• Show consequence of not responding. 

• Do not use blue or green coloration, as those convey low urgency. 

For time critical situations, such as collision avoidance, icons should be positioned so that they attract the driver’s 

attention to the appropriate part of the vehicle or environment.

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Increased line

weight of border

Red lettering

Increased relative

size of the icon

Original Icon Icon Conveying Urgency

Show consequences

of not responding

Red background

Increased line

weight of border

Increased line

Increased relative

Original Icon Icon Conveying Urgency

Show consequences

Increased line

Increased line

Increased relative

Increased line

Increased relative

Original Icon Icon Conveying Urgency

Show consequences

Increased line

Show consequences

Increased line

Increased line

weight of border

Red lettering

Increased relative

size of the icon

Original Icon Icon Conveying Urgency

Show consequences

of not responding

Red background

Increased line

weight of border

Increased line

Increased relative

Original Icon Icon Conveying Urgency

Show consequences

Increased line

Increased line

Increased relative

Increased line

Increased relative

Original Icon Icon Conveying Urgency

Show consequences

Increased line

Show consequences

Increased line

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Caution Snow

Removal

Figure 5-6. Schematic Examples of Conveying Urgency 

 5-14 
 

Discussion: These guidelines enhance perceived urgency by relying on population stereotypes for the interpretation

of red as suggesting danger importance. This has been shown to have a particularly strong influence on perceived

urgency (reference 1). In addition, these guidelines rely on several other icon features that increase their salience, 

such as size, border width, and the use of flashing. These characteristics all enhance the urgency of icons 

individually; combining them magnifies their total effect. 

Icon design features can have a strong effect on the perceived urgency of the icon. However, the perceived urgency

and the driver’s response to urgency depend on the context in which it is perceived. If all in-vehicle messages are 

designed to be perceived as highly urgent, the overall effect will be diluted. To enhance driver response to highly 

urgent messages requires the designer to consider the urgency of the message relative to other potential in-vehicle

messages and tailor icon characteristics to the relative urgency. For example, notification of upcoming tourist

attractions should not include characteristics appropriate for those of a collision avoidance warning.

Design Issues: Color appears to be a powerful mechanism to convey urgency. Text size would need to be doubled 

to generate the same increase in urgency that is seen when the color is changed from black to red (reference 1). 

In addition, urgent symbols or icons should be located where they are most likely to be seen by the driver, thereby 

decreasing driver response time. According to reference 2, the area that is most easily viewed is considered to be a

circular shaped or oval area roughly 10 to 15 degrees in radius around the normal line of sight (which is considered

to be about 15 degrees below the horizon). The figure below indicates the optimal horizontal locations for 

placement of urgent symbols or icons. 

15 degrees 15 degrees

D river’s

Line of Sight

Low er Priority Low e r Priority

Place U rgent or H igh-Pr iority Sym bols in this Space

15o 15o

Figure 5-7. Locations of Icons Within the Visual Field (Adapted from Reference 2)

Cross References:

Flash Rate, p. 4-8; Enhancing Icon Interpretation with Color, p. 5-12; Augmenting Icons with Auditory 

Information, p. 6-2 

References:

1. Adams, A. S., and Edworthy, J. (1995). Quantifying and predicting the effects of basic text display variables on

the perceived urgency of warning labels: Tradeoffs involving font size, border weight and color. 

Ergonomics, 38(11), 2221-2237. 

2. Sanders, M. S., and McCormick, E. J. (1993). Human factors in engineering and design (5th ed.). New York:

McGraw-Hill. 

 5-15 
 

ENHANCING ICON INTERPRETATION WITH SHAPE

Introduction: Enhancing icon interpretation with shape refers to how the shape of an icon’s outside edge or border

can call attention to the hazard level being communicated and enhance drivers’ interpretation of icons. 

Design Guidelines 

• Icons shaped like standard traffic signs convey the respective hazard level of the message. 

• Use octagon-shaped icon borders for high hazard conditions or situations. 

• Use diamond or inverted triangle-shaped icon borders for medium hazard conditions or situations. 

• Use circle, square, or rectangular-shaped icon borders for low hazard conditions or situations. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Hazard Level Shape Recommended Uses Example 

High Octagon

Dangerous road conditions 

Vehicle equipment malfunction 

Road obstruction 

Medium

Diamond 

Inverted triangle 

General road hazards 

Traffic congestion 

Construction warnings 

Low 

Circle 

Square 

Rectangle 

Tourist activities 

Food, lodging, gas 

Navigation instructions

Figure 5-8. Schematic Examples of the Use of Shape in Icons 

 5-16 
 

Discussion: Two warning label shape studies (references 1 and 2) presented subjects with 19 different shapes, 

including traffic safety sign shapes as well as other nontraditional shapes, and used a pairwise ranking procedure to

determine which shapes observers rated as implying the most hazard. The studies found similar results. The 

inverted triangle, diamond, and octagon were perceived as the most hazardous, the circle, square, and rectangle as

the least hazardous. Another study (reference 3) found analogous results with a group of industrial workers and 

using warning signs. Octagon and diamond shaped signs were ranked as more hazardous than circle or square signs. 

Using consistent icon shapes can facilitate rapid recognition (reference 4). This takes advantage of the global 

superiority effect (reference 5), in which the perception of global features in a figure, such as outline shape, is more 

rapid than the perception of local features, such as the icon pictorial. 

Design Issues: The shapes of icons connote different levels of hazard. Research has found that octagon, diamond,

and inverted triangle shapes are perceived as the most hazardous, while circle, square, and rectangle shapes are 

perceived as the least hazardous (references 1, 2, and 3). These preferences are consistent with population 

stereotypes of American road signage displayed in the Manual on Uniform Traffic Control Devices (MUTCD). 

Octagon (“STOP”) and diamond (warning) shaped signs require immediate action or attention. Circular

(“RAILROAD CROSSING”) and rectangle (regulatory) shaped signs generally are used for low priority

information, such as roadside services and speed limit signs. 

Cross References:

Composition of an Icon, p. 2-10; Identifying Icons as Part of a Group, p. 5-8; Conveying Urgency with 

Icons, p. 5-14

References:

1. Cochran, D. J., Riley, M. W., and Douglas, E. I. (1981). An investigation of shapes for warning labels. 

Proceedings of the Human Factors and Ergonomics Society 25th Annual Meeting, 395-399. 

2. Riley, M. W., Cochran, D. J., and Ballard, J. L. (1982). An investigation of preferred shapes for warning labels. 

Human Factors, 24(6), 737-742. 

3. Collins, B. L. (1983). Evaluation of mine-safety symbols. Proceedings of the Human Factors and Ergonomics 

Society 27th Annual Meeting, 947-949.

4. Rogers, Y. (1989). Icon design for the user interface. International Reviews of Ergonomics, 2, 129-154.

5. Pomerantz, J. R. (1983). Global and local precedence: Selective attention in form and motion perceptions. 

Journal of Experimental Psychology: General, 112, 516-540. 

 5-17 
 

CHAPTER 6: THE AUDITORY PRESENTATION OF IN-VEHICLE INFORMATION 

Augmenting Icons with Auditory Information ............................................................................ 6-2 

Determining the Appropriate Auditory Signal ............................................................................ 6-4 

Design of Simple Tones............................................................................................................... 6-6 

Design of Complex Tones ........................................................................................................... 6-8 

Design of Earcons...................................................................................................................... 6-10 

Design of Auditory Icons........................................................................................................... 6-12 

Design of Speech Messages....................................................................................................... 6-14 

Perceived Urgency of Auditory Signals .................................................................................... 6-16 

General Design Guidelines for Automatic Speech Recognition Systems................................. 6-18 

Timing of Auditory Navigation Information ............................................................................. 6-20 

Perceived Annoyance of Auditory Signals................................................................................ 6-22 

 6-1
AUGMENTING ICONS WITH AUDITORY INFORMATION 

Introduction: Augmenting icons with auditory information refers to including some type of auditory signal with an

icon to make the message clearer or more salient. Almost all of the literature suggests that operator performance can

be improved by combining auditory and visual messages. These channels can be used together to provide either

redundant or complimentary cues to the driver. 

Design Guidelines 

• Use the auditory modality for presenting high priority alerts and warnings; present additional contextual 

information visually. 

• Use auditory prompts when a previously static visual display changes.

• Use auditory prompts when high priority information is automatically displayed.

• Use a combination of visual and auditory prompts to repeating low complexity messages.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 6-1. Heuristics for Assessing Priority 

Priority is a function of the urgency of a response and the consequences of failing to make a response. 

High Priority Low Priority

Fast response needed (0–5 minutes) No response needed (5 min +) 

Serious consequences (death or injury) No immediate consequences 

Examples: Notification of serious traffic conditions

that may affect the safety of the driver or mechanical 

problems that could impact the safety of the driver or 

the condition of the vehicle 

Examples: Vehicle maintenance schedules, or weather 

information

Complexity is a function of how much information is being provided and how difficult it is to process. The phrase 

“information units” is used to describe the amount of information presented in terms of key nouns and adjectives 

contained within a message. The design guideline entitled “Design of Speech Messages” on page 6-14 provides a

tool for determining the number of information units. 

Table 6-2. Heuristics for Assessing Complexity 

High Complexity Low Complexity

>9 information units 3–5 information units

Processing time >5 s Processing time <5 s 

Examples: Transit schedules in area along route or 

routing restrictions for specific vehicle cargos 

Examples: Directions of turns or estimates of travel 

costs 

 6-2
Discussion: It is widely believed that combining an auditory and visual presentation of information could improve

operator performance. Reference 1 recommends that the auditory modality be used as: (1) an auditory prompt to

look at a visual display, or (2) supplemental information for a visual display. Providing information in this 

redundant fashion will lessen the need for a driver to scan the visual display and allow him or her to review the 

information if it is not fully understood or remembered. Reference 2 emphasizes the importance of redundant 

coding by stating that presenting information in the auditory and visual modalities will accommodate transient shifts 

in noise within the processing environment (e.g., visual glare, background noise, verbal distractions), which may

influence one format or another. Display format redundancy also accommodates the strengths and abilities of

different population groups (e.g., high spatial ability vs. high verbal ability). 

Design Issues: Reference 3 suggests that, to determine the most appropriate display modality for presenting a 

particular information element, it is extremely important to predict whether the driver will need the information

predrive or in-transit. Then, based upon other issues such as the complexity and urgency of the information, a 

decision can be made regarding which modality will accomplish the goal with the least amount of compromise to 

driver safety. 

In reference 4, a driving simulator was used to study the benefits of multimodal displays (both auditory and visual). 

The multimodal displays were associated with better driving performance than auditory-only or visual-only displays, 

as well as better performance on a navigation task. Both the multimodal and auditory-only displays were associated 

with better emergency responses than the visual-only display. 

Cross References:

Conveying Urgency with Icons, p. 5-14; Determining the Appropriate Auditory Signal, p. 6-4; Design of Speech 

Messages, 6-14

References:

1. Dingus, T. A., and Hulse, M.C. (1993). Some human factors design issues and recommendations for automobile

navigation information systems. Transportation Research, 1C(2), 119-131. 

2. Wickens, C. D. (1987). Information processing, decision-making, and cognition. In G. Salvendy (Ed.), 

Handbook of human factors (pp. 549-574). New York: J. Wiley & Sons. 

3. Mollenhauer, M. A., Dingus, T. A., and Hulse, M. C. (1995). Recommendations for sensory mode selection for 

ATIS displays. Proceedings of the Institute of Transportation Engineers 65th Annual Meeting: A 

Compendium of Technical Papers, 667-672. 

4. Liu, Y., and Dingus, T. A. (1997). Development of human factors guidelines for advanced traveler information 

systems and commercial vehicle operations: Human factors evaluation of the effectiveness of multimodality displays in advanced traveler information systems (FHWA-RD-150). Washington, DC: Federal

Highway Administration.

 6-3
DETERMINING THE APPROPRIATE AUDITORY SIGNAL

Introduction: To determine the appropriate auditory signal means to choose the type of signal (simple tone,

earcon, auditory icon, or speech message) that will best augment the visual message presented to the driver. The 

following auditory signals represent the most frequently used options: 

Simple tones: Single or grouped frequencies presented simultaneously. 

Earcons: Musical tones that can be used in structured combinations to create auditory messages 

(reference 1). These are sometimes referred to as complex tones.

Auditory icons: Familiar environmental sounds that intuitively convey information about the object or action

they represent (reference 2). These are sometimes referred to as naturalistic sounds or

earcons, and are intuitively recognizable. 

Speech messages: Voice messages that add information beyond pure sound. 

Design Guidelines 

• Use simple tones and auditory icons when an immediate response is required. 

• Earcons should be used when it is important for the driver to know that pieces of information are related. 

• Auditory icons are effective for use in collision-warning applications (i.e., horn or skidding tires). 

• Use speech messages when a high degree of message flexibility is required. 

• Use speech messages when a high degree of message detail is required. 

• Use speech messages when the meaning of tones or other sounds may be forgotten under stress. 

• Use speech messages when the auditory message deals with a future point in time for which there must be 

some preparation (i.e., time or distance to turn). 

• Speech message displays should not be used for time-critical tasks. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 6-3. Ratings of Audio Signals for Various Functions 

Functions Example Message Simple 

Tones 

Earcons Auditory

Icons 

Speech 

Messages 

Status indication Navigation system on and

functioning

Good Good Fair Poor

Alerting (attentional) Generic warning indicator (to 

divert attention to a display) 

Good Fair Poor Poor

Warning (informational) Rear-end collision-avoidance 

warning indicator 

Fair Poor Good Fair

Presentation of 

qualitative information

Location of next available 

lodging

Poor Poor Poor Good

Presentation of 

quantitative information

Cost of upcoming toll bridge Poor Poor Poor-Fair Good

 6-4
Discussion: According to reference 3, there are a limited number of tones (five to six) that are absolutely 

recognizable; therefore, they are not a good choice for presenting quantitative information. Also, unless they are 

presented in close temporal sequence, it is difficult to make qualitative judgments regarding deviations. They are 

good, however, for gaining the attention of the driver, whether it be simply for the purpose of getting him or her to

attend to information being presented or to warn of an impending danger. Like tones, earcons are also limited 

because it is difficult to make qualitative judgments regarding deviations from a desired state or value. It is also 

difficult to obtain accurate quantitative information for earcons. Earcons are most effective when presenting a 

family of related sounds (see reference 4). One powerful feature associated with the use of earcons is that “related 

information can be given related sounds and hierarchies of information can be represented” (reference 5). They are 

extremely flexible. However, their meaning is not apparent and must be learned. Therefore, they are not a good 

choice for presenting critical, time-dependent information to the driver. Auditory icons are most effective when

they can be mapped to everyday, naturally occurring sounds (see reference 2). When this is the case, they are 

extremely easy for the user to both learn and remember. They have been shown to be successful in collision 

warning applications (see references 6 and 7) in reducing reaction times to collision events. The problem with

auditory icons, however, is that not all information items to be presented in IVIS systems can be mapped to a 

naturally occurring sound. In these instances, the designer has to create metaphors for the icons, which can end up

being just as abstract as a pure tone or earcon. Speech messages are most effective for rapid, but not automatic, 

communication of complex, multidimensional information; the meaning of the message is intrinsic in the signal and

context, and minimum learning is required. However, speech messages can be inefficient, more easily masked, and 

have problems associated with repeatability and confusions with other sounds in the automobile such as 

conversations and noise from the radio.

Design Issues: Some advantages and disadvantages associated with the use of each of the methods for presenting 

auditory information are given above. This is by no means an exhaustive literature review associated with the use of

the auditory modality, but a tool for aiming the designer in the most appropriate direction. It should also be

mentioned that the auditory signals discussed are being presented as a method for augmenting visual messages or to

act as a redundant cue, not as a sole means for presenting in-vehicle information to the driver. 

Cross References:

Chapter 6: The Auditory Presentation of In-Vehicle Information

References:

1. Brewster, S. A., Wright, P. C., and Edwards, A. D. (1993). An evaluation of earcons for use in auditory humancomputer interfaces. INTERCHI ‘93, 222-27.

2. Gaver, W. W. (1986). Auditory icons: Using sound in computer interfaces. Human-Computer Interaction, 

2(2), 167-177. 

3. Advanced Systems Technology Branch. (1993). Preliminary human factors design standards for airway 

facilities (ACD-350). Atlantic City International Airport, NJ: Federal Aviation Administration Technical 

Center. 

4. Blattner, M. M., Sumikawa, D. A., and Greenberg, R. M. (1989). Earcons and icons: Their structure and 

common design principles. Human-Computer Interaction, 4, 11-44. 

5. Brewster, S. A., Wright, P. C., and Edwards, A. D. N. (1994). A detailed investigation into the effectiveness of 

earcons. In G. Kramer (Ed.), Auditory display: Sonification, audification, and auditory interfaces, Volume 

XVII. Reading, MA: Addison Wesley. 

6. Graham, R., Hirst, S. J., and Carter, C. (1995). Auditory icons for collision avoidance warnings. Proceedings of 

the ITS America 1995 Annual Meeting, 1057-1063. 

7. Belz, S. M., Robinson, G. S., and Casali, J. G. (1998). Auditory icons as impending collision system warning

signals in commercial motor vehicles. Proceedings of the Human Factors and Ergonomics Society 42nd

Annual Meeting, 1127-1131. 

 6-5
DESIGN OF SIMPLE TONES

Introduction: Simple tones are auditory signals that convey information through the use of single or grouped 

frequencies presented simultaneously. For the purposes of this guideline document, simple tones are discussed as a 

means for augmenting the visual presentation of in-vehicle messages and are not meant to be used as the only means 

for presenting in-vehicle messages. 

Design Guidelines 

• Appropriate loudness levels are 15-25 decibels (dB) above the predicted masked threshold. 

• Auditory warning signals should be less than 30 dB above the masked threshold to minimize operator

annoyance and the disruption of communication. 

• The pitch of warning sounds should be between 150 and 1000 Hertz (Hz).

• Continuous tones should be avoided because they are usually high pitched and aversive, prevent 

communication if they are loud, and are easy to habituate because they never change. 

When more than one tone is used:

• Avoid tones with the same on/off ratio. 

• Avoid tones that share the same temporal pattern. 

• Avoid tones that begin in the same way (i.e., with a long tone).

• No more than 6 simple tones should be used. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 6-4. Advantages and Disadvantages Associated with the Use of Simple Tones 

Advantages of Simple Tones Disadvantages of Simple Tones 

• Can serve an alerting function. 

• Can increase detectability of messages. 

• Can produce faster reaction times. 

• Useful in situations where the noise 

environment is too complex for adequate 

voice warnings. 

• Difficult to establish appropriate loudness levels, especially 

in the constantly changing in-vehicle environment. 

• Can be confusing because:

(1) Their meaning is not inherent. 

(2) There may be too many to remember.

• Number of tones that can be reliably discriminated is low.

• Can induce startle responses. 

• Difficult to prioritize or determine perceived urgency. 

 6-6
Discussion: Simple tones are similar to arbitrary symbols and only become meaningful through learning. Their 

main function is to alert the driver to a situation or event. The event could be an impending collision, or it could be

simply a display of additional information via text, voice messages, or even in-dash indicators. There are many

instances for which a simple tone may be appropriate; however, it is important to limit their use to no more than six 

per display (reference 1). 

Design Issues: One of the central problems associated with a simple auditory tone is loudness. In the vehicle, the

noise level is constantly changing; the driver may be speeding down the interstate with the windows down, chatting

with a passenger, listening to the radio, or sitting quietly at a stoplight. In each of these situations, the appropriate 

level for presenting auditory information varies. Warnings that are too loud can: (1) be shut off; (2) cause the driver

to be attending to the warning when he/she should be attending to the situation it is warning of; (3) distract from the 

main task; or (4) startle the driver, causing an inappropriate response. However, warnings that are not loud enough 

are likely to be missed. Therefore, determining the appropriate auditory threshold is extremely important. See

references 2 and 3 for guidelines regarding the range for predicting thresholds and constructing auditory warning

systems. 

Cross References:

Determining the Appropriate Auditory Signal, p. 6-4 

References: 

1. Advanced Systems Technology Branch. (1993). Preliminary human factors design standards for airway 

facilities (ACD-350). Atlantic City International Airport, NJ: Federal Aviation Administration Technical 

Center. 

2. Patterson, R. D. (1982). Guidelines for auditory warnings systems on civil aircraft (Civil Aviation Authority 

paper 82017). London: Civil Aviation Authority. 

3. Zwicker, E., and Scharf, B. (1965). A model of loudness summation. Psychological Review, 72, 3-26. 

 6-7
DESIGN OF COMPLEX TONES

Introduction: Complex tones are auditory signals that present information through the use of a hierarchical nesting 

of pulses and bursts that combine to form the signal or sound. The parameters of complex tones can have an

important effect on perceived urgency, annoyance, and appropriateness. 

Design Guidelines 

• The amplitude envelope of the initial pulse should include a 20 millisecond (ms) onset to reduce startle 

effects. 

• The pulse should be composed of multiple frequency components, such as formants or harmonics, to mitigate 

masking due to background noise. 

• The temporal pattern of auditory signals should be as distinct as possible, otherwise confusion is likely, even 

if the spectral content is substantially different. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

High-density, low-speed signal

Low-density, lo-swpeed signal

High-density, hig-hspeed signal

Gradual onset, gradual offset

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

High-density, low-speed signal

Gradual onset, gradual offset

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

Gradual onset, gradual offset

Low-density, low-speed signal

High-density, high-speed signal

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

High-density, low-speed signal

Low-density, lo-swpeed signal

High-density, hig-hspeed signal

Gradual onset, gradual offset

High-density, low-speed signal

Low-density, lo-swpeed signal

High-density, hig-hspeed signal

Gradual onset, gradual offset

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

High-density, low-speed signal

Gradual onset, gradual offset

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

Pulse

(Acoustic waveform)

Burst

(Set of pulses)

Auditory signal

(Set of bursts)

100 ms

500 ms

2,000 ms

Gradual onset, gradual offset

Low-density, low-speed signal

High-density, high-speed signal

Figure 6-1. Temporal Parameters of Auditory Signals—Pulse, Burst, and Sound Parameters Defined 

Graphically

Temporal parameters of the pulse, burst, and sound:

Duration: The time from the beginning to the end of a pulse or burst. 

Inter-pulse interval: The time between the end of one pulse or burst and the beginning of the next. 

Inter-burst interval: The time between the end of one pulse or burst and the beginning of the next. 

Speed: The time between the beginning of a pulse or burst to start of the next. 

Density: Pulse or burst duration divided by pulse speed. 

Onset time: The time from the start of the pulse or burst until it reaches maximum output. 

Offset time: The time in which the pulse or burst falls from maximum output to zero. 

Duty cycle: Number of pulses per second. 

 6-8
Discussion: Pulses combine to form bursts and bursts combine to form the overall auditory signal. Pulses, bursts, 

and the sound all have temporal sound parameters that affect confusion, urgency, and annoyance. This hierarchy of

sound parameters is defined by the timescale, where the timescale of the pulse is from 100 to 300 ms and the 

timescale of the burst is 500 to 2,000 ms. The complete warning signal ranges from 2,500 ms to tens of seconds. 

The harmonic content that defines the timbre or formant also has a powerful effect on the perception of the alert 

(reference 1). A signal composed of a harmonic frequency series is substantially less urgent than one composed of a 

random or partially random frequency series (reference 1). The formant determines the characteristic quality of

vowel sounds and is composed of several frequency regions of relatively great intensity. More specifically, a 

formant is a resonant peak in the frequency spectrum of a voice and is a critical acoustic feature of most speech 

sounds. Formants are different than more common combinations of frequency components, such as harmonic series. 

Rather than being equally spaced across the frequency spectrum, formants are distributed in an apparently random

distribution. The critical attribute of a formant is that it determines the characteristic quality of vowel sounds 

produced by humans. Formants reflect anatomical properties of the vocal tract and are fundamental characteristics 

of natural speech sounds and seem more likely to influence emotional content of a sound compared to artificial 

frequency combinations, such as octaves. Research has shown that formants affect the perception of sound 

characteristics related to urgency and annoyance (reference 2). 

Design Issues: 

The parameters that affect perception at the level of the sound may not have the same effect at the level of the burst. 

For example, pulse onset has a different effect than the onset of the entire signal. A slow onset at the level of the 

pulse increases urgency, whereas longer onsets at the burst or signal level decrease urgency. This result suggests

that empirical findings regarding the effect of temporal parameters on pulse perception may not generalize to burst

perception. 

Cross References:

The Auditory Presentation of In-Vehicle Information, p. 6-1; Perceived Urgency of Auditory Signals, p. 6-16; 

Perceived Annoyance of Auditory Signals, p. 6-22

References:

1. Edworthy, J., and Adams, A. (1996). Warning design: A research perspective. Bristol, PA: Taylor and Francis.

2. Stanford, L. M., McIntyer, J. W. R., Nelson, T. M., and Hogan, J. T. (1988). Affective responses to commercial 

and experimental auditory alarm signals for anesthesia delivery and physiological monitoring equipment.

International Journal of Clinical Monitoring and Computing, 5, 111-118. 

 6-9
DESIGN OF EARCONS

Introduction: Earcons refer to auditory signals that present information through abstract musical tones that can be used in

structured combinations to create auditory messages (reference 1). Earcons are also sometimes referred to in the literature as

complex tones. Earcons have five parameters that can be modified to create different messages: rhythm, pitch, timbre, register, 

and dynamics. 

Rhythm: Whole note, dotted half note, half note, quarter note, dotted eighth note, eighth note, sixteenth note. 

Pitch: Eight octaves of 12 pitches each.

Timbre: Sinusoidal, sawtooth, triangular, rectangular. 

Register: Low, medium, high. 

Dynamics: Soft, medium, loud, soft to loud, loud to soft. 

A motive, the building block of an earcon, is defined as “a rhythmicized sequence of pitches. Rhythm and pitch are the fixed 

parameters of a motive, while timbre, register, and dynamics are the variable parameters of motives” (reference 2). 

Design Guidelines 

• Use synthesized musical timbres that are subjectively easy to tell apart (i.e., organ and brass). 

• Do not use pitch alone to distinguish between tones unless there are very significant differences. Some suggested ranges 

for pitch are max: 5 kHz and min: 125 Hz–150 Hz. 

• Use tones that are three or more octaves apart. 

• Make the rhythm as different as possible. Putting a different number of notes in each rhythm is effective.

• Some suggested ranges for intensity are max: 20 dB above threshold and min: 10 dB above threshold. 

• When playing combinations of multiple earcons, a gap of 0.1 second should be between them so that the user can tell 

where one finishes and another starts. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 6-5. Three Methods for Constructing Earcons (from Reference 3)

Method Description Example 

Combining The process of combining to create an earcon means

linking different motives together in a chain-like 

sequence. Let A and B be earcons that represent

different messages. A and B can be combined by

linking A and B to form a third earcon AB.

A = urgent 

B = e-mail 

AB = urgent e-mail

Transforming The process of transformation cosmetically alters a 

motive by changing its timbre, register, and/or tempo. 

However, it is important not to alter the motive beyond

recognition. The semantic implications are a change of 

state in an object, not a change of object. Earcon A

may be transformed into earcon B by modification in 

the construction of A. 

A = system up

A’ or B = system down

Inheriting The process of inheriting is one in which a single

earcon is heard in an increasingly complex chain.

Imagine a tree of earcons with a family motive at the 

root. The next level adds pitch to the rhythm of the 

family motive. At the next level, a recognizable timbre 

is added.

A = the family motive (i.e., in-vehicle 

messaging) 

A + pitch = AB (i.e., message received) 

AB + timbre = ABC (i.e., message forwarded)

 6-10 
Discussion: Earcons are said to be a powerful and flexible means for creating auditory messages (see references 2, 

3, 4, and 5). Reference 3 argues that the advantages associated with the use of earcons are clear: (1) they are easily 

constructed on any workstation or personal computer; (2) the sounds do not have to correspond to the objects they

represent, so objects that either make no sound or that make an unpleasant sound can be represented; and (3) studies 

have shown that they are preferred over other types of auditory communication (see reference 6). The main

disadvantage, however, is that, like simple tones, earcons must be learned. Their meaning is not inherent in the 

signal.

Design Issues: Reference 4 presents extensive, very specific guidelines for developing earcons, examining such

issues as the psychoacoustical characteristics of sound, the formal arrangement of sounds into earcons, and the 

meaning and interpretation of earcons. Reference 5 presents slightly more general information. However, the 

concepts discussed require some knowledge of the parameters associated with sound. References 4 and 5 argue that

experts, such as professional composers, should be included on any design team that is attempting to construct

earcons. “The science of sound is a highly technical, diverse, and complicated discipline. Only an expert in this 

field understands the existence, importance, implications, and consequences of and the means of dealing with, the 

many perceptual problems and intricacies of sound” (reference 2). 

For the purposes of this guideline document, earcons are discussed as a means of augmenting the visual presentation 

of in-vehicle messages and are not meant to be used as the only way to present in-vehicle messages. 

Cross References:

Determining the Appropriate Auditory Signal, p. 6-4; Perceived Urgency of Auditory Signals, p. 6-16

References:

1. Brewster, S. A., Wright, P. C., and Edwards, A. D. (1993). An evaluation of earcons for use in auditory humancomputer interfaces. INTERCHI ‘93, 222-227. 

2. Blattner, M. M., Sumikawa, D. A., and Greenberg, R. M. (1989). Earcons and icons: Their structure and 

common design principles. Human-Computer Interaction, 4, 11-44. 

3. Blattner, M. M. (1993). Sound in the multimedia interface (LLNL TR W-7405-Eng-48). Livermore, CA: 

Lawrence Livermore National Laboratory.

4. Sumikawa, D. A. (1985). Guidelines for the integration of audio cues into computer user interfaces (UCRL 

53656). Livermore, CA: Lawrence Livermore National Laboratory.

5. Sumikawa, D. A., Blattner, M. M., Joy, K. I., and Greenberg, R. M. (1986). Guidelines for the syntactic design

of audio cues in computer interfaces (UCRL-92925-REV.1). Livermore, CA: Lawrence Livermore 

National Laboratory.

6. Jones, S. D., and Furner, S. M. (1989). The construction of audio icons and information cues for human 

computer dialogues. Contemporary Ergonomics 1989. Proceedings of the Ergonomics Society’s 1989 

Annual Conference, 436-441.

 6-11 
DESIGN OF AUDITORY ICONS

Introduction: Auditory icons are familiar environmental sounds that intuitively convey information about the 

object or action that they represent (reference 1). They are sometimes also referred to in the literature as naturalistic 

sounds or earcons. The three types of auditory icon are iconic, metaphorical, and symbolic. 

• Iconic auditory icons sound like the object or action they represent (e.g., the sound of a crash to indicate a 

collision warning). 

• Metaphorical auditory icons sound like some element of the object or action they represent (e.g., the sound of

children to indicate a school crossing). 

• Symbolic auditory icons rely on social convention for meaning (e.g., the sound of a siren to indicate an 

ambulance approaching). 

The figure below (from reference 2) demonstrates some of the performance improvements that might be obtained 

when using an auditory icon for a warning component. 

Design Guidelines 

• By definition, auditory icons must be identifiable as having relevance or conveying some inherent meaning

(see above for examples of iconic, metaphorical, and symbolic auditory icons). 

• Auditory icons should be detectable 10 to 20 dB above the masked threshold. 

• No more than six auditory icons should be used in an auditory icon set. 

• Auditory icons should strive to attract the attention of the driver without generating a startle reaction. Special 

attention should be paid to the perceived urgency associated with different candidate auditory icons. 

Based Equally on Expert Judgment

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0.65

0.7

0.75

0.8

0.85

0.9

Horn Tire Skid Speech Tone

Warning Sounds

Stationary Vehicle Ahead

Vehicle Pulling Out from Side Road

Mean Braking Reaction Time

Figure 6-2. Brake Reaction Times for Different Warning Sounds (from Reference 2)

 6-12 
Discussion: The goal of auditory icon design is to map the attributes of a computer event to some everyday soundproducing event (see references 1 and 3). This makes auditory icons extremely easy for users to learn and 

remember, as their meaning is inherent. Perhaps this is why they have been examined for use in collision warning

applications. One could argue that drivers’ responses would be based on experiences in which they have heard these 

sound occur naturally, thus their responses will be faster. This has, in fact, been shown to be the case. Reference 2

describes a study in which drivers were required to carry out a tracking task while at the same time attending to a 

road scene interspersed with imminent collisions. They were asked to respond to each collision warning they were 

given and determine the appropriate braking response. Four collision warnings were tested (a simple tone; a speech

warning “ahead”; the sound of a car horn; and the sound of skidding tires). Results of the study showed that braking 

reaction times were faster for the auditory icons than for the more traditional warning sounds. Another study 

described in reference 4, found similar results. Braking reaction times for collision warnings using auditory icons

were shown to be significantly less than for conventional collision warnings (tones). 

Design Issues: While the experiments described above show an improved braking reaction time associated with the

use of auditory icons in collision warning applications, the icons are not necessarily the best choice for presenting

this type of information. In addition to producing faster braking reaction times, they also produced a higher number 

of inappropriate reactions due to startle effects (e.g., slamming on brakes for a low-level warning; see reference 2). 

This type of reaction could actually negate any benefits of having a collision warning system and potentially put the 

driver’s safety at risk. Ensuring that the appropriate level of urgency is projected to the driver is a very important

design issue. References 5 and 6 suggest that factors such as the frequency, amplitude, envelope shape, and melodic 

structure of a warnings can all affect perceived urgency. Thus, altering certain sound parameters may allow a 

designer to reduce the startling affect of these type of warnings. 

For the purposes of this guideline document, auditory icons are discussed as a means for augmenting the visual 

presentation of in-vehicle messages and are not meant to be used as a sole means for presenting in-vehicle messages. 

Cross References:

Determining the Appropriate Auditory Signal, p. 6-4; Perceived Urgency of Auditory Signals, p. 6-16

References:

1. Gaver, W. W. (1986). Auditory icons: Using sound in computer interfaces. Human-Computer Interaction, 

2(2), 167-177. 

2. Graham, R., Hirst, S. J., and Carter, C. (1995). Auditory icons for collision avoidance warnings. Proceedings of 

the ITS America 1995 Annual Meeting, 1057-1063. 

3. Gaver, W. W. (1989). The sonic finder: An interface that uses auditory icons. Human-Computer Interaction, 

4(1), 67-94.

4. Belz, S. M., Robinson, G. S., and Casali, J. G. (1998). Auditory icons as impending collision system warning

signals in commercial motor vehicles. Proceedings of the Human Factors and Ergonomics Society 42nd

Annual Meeting, 1127-1131. 

5. Edworthy, J., Loxley, S., and Dennis, I. (1991). Improving auditory warning design: Relationship between 

warning sound parameters and perceived urgency. Human Factors, 33(2), 205-231.

6. Hellier, E. J., Edworthy, J., and Dennis, I. (1993). Improving auditory warning design: Quantifying and 

predicting the effects of different warning parameters on perceived urgency. Human Factors, 35(4), 693-

706. 

 6-13 
DESIGN OF SPEECH MESSAGES

Introduction: Speech messages refer to auditory signals that present information through voice messages that add 

information beyond pure sound. For the purposes of this guideline document, speech is discussed as a means for

augmenting the visual presentation of in-vehicle messages and is not meant to be used as the only means of

presenting in-vehicle messages. 

Design Guidelines 

• If speech must be used in a time-critical application (i.e., warning), the message should be kept to a single 

word or a short phrase with the fewest number of syllables possible. 

• Messages that are not urgent or for which a response may be delayed can be a maximum of seven units of

information in the fewest number of words possible. If the information cannot be presented in a short

sentence, the most important information should be presented at the beginning and/or the end of the message. 

• Navigation instructions should be limited to three or four information units (i.e., “Accident ahead, merge 

right” or “Turn right in 1⁄2 mile”). 

• Do not try to make the voice sound too human. A machine should have a machine voice to cue its identity 

when it speaks. 

• Provide a means for repeating speech messages. 

• Provide a redundant visual presentation of the information being presented aurally. 

Based Equally on Expert Judgment

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Table 6-6. Determining the Number of Information Units 

Message Type Number of Information Units Example Message 

Urgent message 

(i.e., collision warning)

1 unit Brake

Navigation instructions 3–4 units Road Construction Ahead at

Jaspertown

Non-urgent message 

(i.e., motorist services) 

7 units Gas Station Ahead 

Exit #46

Turn Right

Table 6-7. Examples of Auditory Messages 

Suggested Not Suggested

“Oil change needed by July 1, 2003.” “Vehicle maintenance log shows that vehicle oil 

change is due and should be completed by July 1,

2003.” 

“Turn right in 1⁄2 mile.” “At the next stoplight, turn right onto Stark Lane in 1⁄2 

mile.” 

 6-14 
Discussion: Speech displays are an effective means for communicating information to the driver. In addition to 

warning, they can be used to provide responses to user queries and feedback from control inputs. Warnings, 

however, have received the majority of attention in speech display research. They are effective in that they not only 

alert the driver to an emergency situation, but they also provide additional information about the nature of the 

problem (reference 1). However, the added length of the message can increase the driver’s response time. 

Therefore, an important tradeoff exists between comprehension and clarity (i.e., message length) and driver response 

times. The guidelines given on the previous page should aid designers in making this tradeoff. 

Design Issues: When presenting messages that do not require immediate action, reference 2 suggests several

options exist for helping the driver use the information: (1) present the information in the order of importance or

relevance to the driver; (2) present the most important information at either the beginning or the end of the message 

because it is easiest to recall; (3) highlight the most important parts of the message; (4) provide a means for 

repeating the message—this is especially helpful for older drivers; and (5) provide a redundant visual presentation of

the information—this is also helpful for older drivers. 

One important design decision is whether to include an alerting tone before presenting a voice message. References

3, 4, and 5 found that voice warnings preceded by an alerting tone did not produce faster response times than the

voice warning by itself. However, in one study, an alerting tone actually increased response time (see reference 3). 

Reference 6 supports the notion that synthesized speech is distinctive from human speech and can perform an 

alerting function in addition to transferring the pertinent information to the driver. This is another reason for making

sure that we do not try to make the speech warnings sound too human. A machine-like voice will better cue the 

driver to its identity. 

Another important consideration when determining whether to use speech displays is driver acceptance. Existing 

research indicates that speech displays should be used sparingly because the auditory channel can quickly become

cluttered or overloaded with stimuli (references 7, 8, and 9). Speech displays are inherently intrusive and have a 

tendency to annoy the user if they are presented too frequently. In fact, speech displays used in certain aircraft 

applications have even been disabled so that the pilots would not have to listen to the chatter of redundant or

irrelevant messages. Because of the potential problems of acceptance, speech displays should only be used when the 

visual modality is overloaded, and they should always be accompanied by a visual representation so that the 

information can be referred to again at a later time (reference 9). 

Cross References:

Determining the Appropriate Auditory Signal, p. 6-4 

References:

1. Wogalter, M. S., and Young, S. L. (1991). Behavioural compliance to voice and print warnings. Ergonomics, 34(1), 

78-89. 

2. Ross, T., Midtland, K., Fuchs, M., Pauzie, A., Engert, A., Duncan, B., Vaughan, G., Vernet, M., Peters, H., Burnett, G., 

and May, A. (1996). HARDIE design guidelines handbook: Human factors guidelines for information 

presentation by ATT systems (DRIVE II Project V2008). 

3. Simpson, C. A., and Williams, D. H. (1980). Response time effects of alerting tone and semantic context for 

synthesized voice cockpit warnings. Human Factors, 22(3), 319-330. 

4. Hakkinen, M. T., and Williges, B. H. (1984). Synthesized warning messages: Effects of an alerting cue in single- and 

multiple-function voice synthesis systems. Human Factors, 26(2), 185-195. 

5. Bucher, N. M., Karl, R. L., Voorhees, J. W., and Werner, E. (1984). Alerting prefixes for speech warning messages. 

IEEE Proceedings of the National Aerospace and Electronics Conference, Volume 2 (pp. 924-931). 

6. Cowley, C. K., and Jones, D. M. (1992). Synthesized on digitized? A guide to the use of computer speech. Applied 

Ergonomics, 23(3), 172-176. 

7. Wickens, C. D. (1992). Engineering psychology and human performance (2nd edition). New York: Harper-Collins. 

8. Stokes, A., Wickens, C., and Kyte, K. (1990). Display technology: Human factors concepts. Warrendale, PA: 

Society of Automotive Engineers. 

9. Wierwille, W. W. (1993). Visual and manual demands of in-car controls and displays. In B. Peacock and W.

Karwowski (Eds.), Automotive ergonomics (pp. 229-320). London: Taylor and Francis. 

 6-15 
PERCEIVED URGENCY OF AUDITORY SIGNALS

Introduction: Perceived urgency of auditory signals refers to the subjective impression of urgency that a signal gives to the

person hearing it. The goal is to match the urgency of the auditory signal to the urgency of the situation to which it pertains. 

This is called “urgency mapping.” Reference 1 has shown that the perceived urgency of an auditory signal can be directly

manipulated by changing certain temporal or melodic parameters, such as speed, rhythm, number of units, speed change, 

fundamental frequency, pitch range, pitch contour, and musical structure. 

Temporal Parameters 

Speed (slow = 1.5 pulse/sec; fast = 6 pulse/sec)

Rhythm (regular = all pulses equally spaced; 

 irregular = pulses not equally spaced)

Number of units (1 = 1-4 pulse burst; 4 = 4-4 pulse bursts)

Speed change (slowing down; speeding up)

Melodic Parameters

Fundamental frequency (low = 200 Hz; high = 800 Hz) 

Pitch range (small = 3 semitones; large = 9 semitones) 

Pitch contour (down/up; random) 

Musical structure (resolved = from natural scales; 

 atonal = random sequence of pulses)

Design Guidelines 

To increase the perceived urgency:

• Use faster auditory signals. 

• Use regular rhythms. 

• Use a greater number of units (4).

• Use auditory signals that speed up. 

• Use high fundamental frequencies. 

• Use a large pitch range. 

• Use a random pitch contour. 

• Use an atonal musical structure.

To decrease the perceived urgency: 

• Use slower auditory signals. 

• Use irregular rhythms. 

• Use fewer number of units (1).

• Use auditory signals that slow down. 

• Use low fundamental frequencies.

• Use a small pitch range. 

• Use a down or up pitch contour. 

• Use a resolved musical structure. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

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Log10 (O)

Log10 (S)

m = the slope

of the line of

best fit

k = the intercept

of the line of

best fit

1.5

1.55

1.6

1.65

1.7

1.75

1.8

1.85

2.7 2.8 2.9 3 3.1 3.2

Where:

S = Subjective value of Perceived Urgency rating

(note: range of subjective scale was 0 to 100.)

O = Objective value of a sound parameter

Figure 6-3. Example of Using Steven’s Power Law for Producing Urgency Exponents 

(see references 2 and 3 for more detailed explanations and examples) 

 S = kOm (8)

 6-16 
Discussion: The perceived urgency of auditory signals has been researched to some extent in the past 10 years. The 

results have shown that varying certain acoustical parameters has a strong and consistent effect on a person’s 

subjective impression of the urgency of the warning. Reference 1 provides designers with a database concerning the

subjective ratings and rankings of the perceived urgency of many of the temporal and melodic parameters. 

Designers can use this information to produce warnings with the appropriate levels of perceived urgency. This is

extremely important, as new research has discovered that increases in the perceived urgency of a warning correlates 

with faster reaction times (see references 4 and 5). Therefore, if auditory signals are designed with urgency

mapping in mind, more effective warnings can be developed. 

Design Issues: References 2 and 3 show how, using Steven’s power law, certain quantifiable sound parameters

such as speed, number of repetitions, and frequency can be scaled and compared directly. In reference 3, urgency 

exponents for speed, number of repetitions, and frequency were calculated to be 1.35, 0.5, and 0.38, respectively. 

Because speed has a higher urgency exponent, it means that the subjective assessment of urgency changes faster as 

the change in speed increases. Reference 6 states that these results imply that a small change in the speed of a 

warning increases its urgency considerably, whereas a much larger change in the number of repetitions would be

required to produce the same change. The ability to quantify this subjective assessment allows designers of IVIS to

develop a set of auditory signals that would sound different but, through a manipulation of certain parameters, would 

have the same urgency.

Reference 7 suggests that urgency mapping tests be carried out on sets of auditory signals being used as alarms, 

especially if they are abstract alarm sounds. The first step in this process is to get a group of people who have a 

good working knowledge of the environments in which the alarms will be used to rate the situational urgency of the 

referents on a scale from 1 to 5. The second step is to have a different group of people rate on a scale from 1 to 5 the

psychoacoustical urgency of the auditory warnings, without any knowledge of the referents. The next step is to

correlate the two measures. If there is a significant correlation, then the designer may decide to make little or no

changes to the alarm. However, if there is no correlation or a negative correlation, then the designer should modify 

the alarm. The list on the previous page may help a designer choose which parameters to alter and how to alter them

to make an alarm more or less urgent. 

Cross References:

Design of Earcons, p. 6-10; Design of Auditory Icons, p. 6-12

References:

1. Edworthy, J., Loxley, S., Geelhoed, E., and Dennis, I. (1989). The perceived urgency of auditory warnings. 

Proceedings of the Institute of Acoustics, 11(5), 73-80.

2. Hellier, E. and Edworthy, J. (1989). Quantifying the perceived urgency of auditory warnings. Canadian

Acoustics, 17(4), 3-11. 

3. Hellier, E., Edworthy, J. and Dennis, I. (1993). Improving auditory warning design: Quantifying and predicting

the effects of different warning parameters on perceived urgency. Human Factors, 35(4), 693-706.

4. Haas, E. C. and Casali, J. G. (1995). Perceived urgency and response time to multi-tone and frequency

modulated warning signals in broadband noise. Ergonomics, 38(11), 2313-2326. 

5. Burt, J. L., Bartolome, D. S., Burdette, D. W., and Comstock, J. R. (1995). A psychophysiological evaluation of

the perceived urgency of auditory warning signals. Ergonomics, 38(11), 2327-2340. 

6. Edworthy, J. (1994). The design and implementation of non-verbal auditory warnings. Applied Ergonomics, 

25(4), 202-210.

7. Edworthy, J., and Stanton, N. (1995). A user-centered approach to the design and evaluation of auditory

warning signals: 1. Methodology. Ergonomics, 38(11), 2262-2280. 

 6-17 
GENERAL DESIGN GUIDELINES FOR AUTOMATIC SPEECH RECOGNITION SYSTEMS

Introduction: Automatic Speech Recognition (ASR) devices recognize human speech and, in an in-vehicle 

context, treat speech commands as inputs to an IVIS device. Currently, ASR is viewed as an enabling technology in 

intelligent transportation system (ITS) development. Many of the state-of-the-art advances associated with ITS 

involve complex in-vehicle devices that include a host of functions including: navigation, e-mail, motorist services, 

internet access, cellular phone capabilities, “infotainment,” and fax. Such broad functionality is associated with 

greater perceptual, information processing, and psychomotor demands on the driver, and presents a crucial challenge

to IVIS developers. ASR is viewed as a means to allow the driver to interact with the IVIS device, while 

maintaining his/her eyes on the road and hands on the wheel. Moreover, recent advances in ASR techniques

(speaker independent devices, increased vocabulary size, reduced processing time, noise-filtering and

word-matching algorithms) suggest that it may be an attractive alternative to traditional approaches to the 

driver-vehicle interface (DVI). 

Design Guidelines 

• For IVIS applications, ASR devices should be used to aid complex tasks that involve high visual, cognitive, 

or manual requirements. 

• Vocabulary sets for ASR devices should: reflect natural language conventions as much as possible, avoid 

similar-sounding words or phrases, and be small enough so that drivers can recall command words rapidly

and with few or no errors. 

• The microphone for an ASR device should be located on the forward portion of the vehicle headliner, right in

front of the driver (reference 3). 

• Drivers should be provided with immediate feedback (e.g., error correction, input confirmation) of the 

recognition results or the system's response to the speech input. Changes in the visual display itself provide a 

good form of feedback, but require driver head or eye movements to verify. Although any feedback will 

improve the driver's performance with the system, size limits on IVIS displays in the in-vehicle environment, 

as well as concerns about visual overload, suggest that auditory feedback should be used.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

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Table 6-8. Issues to Consider When Designing ASR Systems 

Task-Related Issues Environment-Related Issues Operator-Related Issues 

• Single versus dual task. 

• Workload. 

• Head movement requirements. 

• Driving situation (e.g., effects of 

stress). 

• Requirements for feedback. 

• Vocabulary requirements. 

• External noise (e.g., traffic, road 

noise). 

• Internal noise (e.g., entertainment 

system, conversation). 

• Vibration. 

• Acceleration/deceleration G-forces. 

• Age.

• Articulation.

• Regional accents. 

• Level of training. 

• Gender. 

 6-18 
Discussion: Reference 1 discusses a variety of issues and research results associated with speech controls, and 

some of the guidelines above have been adapted from the design principles presented in reference 1 and, to a lesser 

extent, reference 2. 

Reference 3 investigated ASR performance using a recorded, multispeaker database and seven candidate 

microphone positions. Evaluation criteria included signal-to-noise ratio (SNR) and recognition rate. A range of

locations (e.g., center dashboard, ceiling near rearview mirror, visor on headliner in front of the driver, over driver 

head, and on the steering wheel) were investigated. Although all microphone positions were roughly near the driver, 

great variability was reported (between 0 percent and 10 percent) in error rates across the seven positions. The 

location on the forward portion of the vehicle headliner, right in front of the driver, gave the best combined results 

for both SNR and recognition rates. However, this issue has not been extensively studied and the optimum

microphone location may vary across different in-vehicle applications. 

Reference 4 investigated six options for providing feedback with an ASR device. The options included auditory or

visual feedback, delay prior to feedback, and no feedback. In the study, subjects entered fields of data into an ASR

device. These data consisted of alphanumeric characters, words, or numbers plus words, and were of varying

length. With no feedback, only 70 percent of the entered fields were error-free; the average number of correctly

entered fields across the feedback conditions (any feedback) was 97 percent. The authors noted some tradeoffs 

between visual and auditory feedback, with visual word feedback being optimal when a large visual display is

available to the user. However, in situations with small displays or when visual overload of the user is a concern 

(such as in the in-vehicle environment), auditory feedback is recommended. 

Design Issues: As noted in reference 1, key issues in the design and implementation of ASR systems include:

• Recognition accuracy: Lower accuracies will reduce system performance and user acceptance. 

• Background noise: Ambient noise (traffic, radio, speech displays) can interfere with ASR system performance. 

• Speech variability: Human speech varies considerably with respect to volume, frequency, pitch, and tone under 

different conditions, in addition to accents and regional variations. Speech variability can contribute to reduced 

recognition of speech.

• Task selection: Selection of tasks for which speech should be used must reflect task characteristics and a clear 

understanding of the tradeoffs associated with using speech controls vs. manual controls. 

In addition, use of ASR does not ensure safe operation of an in-vehicle device. Even simple speech requires 

cognitive operations by the user (e.g., recalling phone numbers). In general, ASR is best used as a redundant source 

of input by the driver (i.e., an alternate manual means should be provided to the driver as well). 

Cross References:

Chapter 10: Sensory Modality Design Tool

References:

1. Simpson, C. A., McCauley, M. E., Roland, E. F., Ruth, J. C., and Williges, B. H. (1987). Speech controls and

displays. In G. Salvendy (Ed.), Handbook of human factors (pp. 549-574). New York: J. Wiley & Sons. 

2. McMillan, G. R., Eggleston, R. G., and Anderson, T. R. (1997). Nonconventional controls. In G. Salvendy

(Ed.), Handbook of human factors and ergonomics (pp. 729- 771). New York: J. Wiley & Sons. 

3. Smolders, J., Claes, T., Sablon, G., and Van Compernolle, D. (1994). On the importance of the microphone 

position for speech recognition in the car. Proceedings of the 1994 IEEE International Conference on 

Acoustics, Speech, and Signal Processing, Volume 1 (pp. 429-432).

4. Schurick, J. M., Williges, B. H., and Maynard, J. F. (1985). User feedback requirements with automatic speech 

recognition. Ergonomics, 28(11), 1543-1555. 

 6-19 
TIMING OF AUDITORY NAVIGATION INFORMATION

Introduction: The timing of auditory navigation information refers to the time or distance at which the in-vehicle 

navigation system should present an auditory instruction to the driver before an approaching navigation maneuver 

(e.g., a required turn). 

Design Guidelines 

• For maneuvers defined as leaving the current route (i.e., turning onto a side road), the timing of the auditory

guidance instruction can be based on the equations provided below. 

• It may be advisable to implement the equation for “preferred maximum distance.” An instruction given

slightly too early is preferable to one given too late. 

• When the distance between two subsequent maneuvers is less than the minimum preferred distance for that

speed, the instructions are “stacked” (given during a single message).

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

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and Experimental Data

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Based Primarily on

Experimental Data

Preferred Maximum Distance = 144 meters

Preferred Minimum Distance = 93 meters

Ideal Distance = 116 meters

Vehicle Speed =

48 kph (30 mph)

EQUATIONS1

= (Speed x 1.637) + 14.799

= (Speed x 1.973) + 21.307

= (Speed x 2.222) + 37.144

Preferred Minimum Distance (9)

Ideal Distance (10)

Preferred Maximum Distance (11)

Example of the Suggested Timing for Navigational Information

1 where speed is in km/h and distances are in meters

50 m

100 m

150 m Preferred Maximum Distance = 144 meters

Preferred Minimum Distance = 93 meters

Ideal Distance = 116 meters

Vehicle Speed =

48 kph (30 mph)

EQUATIONS1

= (Speed x 1.637) + 14.799

= (Speed x 1.973) + 21.307

= (Speed x 2.222) + 37.144

Preferred Minimum Distance (9)

Ideal Distance (10)

Preferred Maximum Distance (11)

Example of the Suggested Timing for Navigational Information

1 where speed is in km/h and distances are in meters

50 m

100 m

150 m

Figure 6-4. Equations for Determining the Appropriate Timing of an Instruction 

 6-20 
Discussion: In reference 1, subjects were asked to give a subjective rating of the timeliness of auditory navigation 

instructions (1 = much too early to 6 = much too late). From the subjects’ ratings, regression lines were plotted. 

Three separate equations were developed for calculating the distance at which navigation information should be 

given regarding an approaching turn onto a side road, while traveling at different speeds. 

Reference 2 conducted a similar study aimed at determining the last possible moment at which a subject would feel

comfortable hearing an auditory navigational instruction. The results of this study indicated that, traveling at speeds

of 65 kph (40 mph), the recommended distance for giving navigational instructions before a turn is 137 meters (450

feet). However, it is necessary to make adjustments for other speeds (15 feet for each mile per hour/4.58 meters for 

each kilometer per hour); age of driver (up to 36 meters (119 feet)); the direction of turn, left or right (left turns

require more warning distance); and gender of the driver. The results of this study are similar to those found in 

reference 1 but were determined to be more difficult to apply to the general driver population.

Design Issues: The applicability of these guidelines to visual guidance messages is uncertain. Since visual 

information (with no accompanying auditory alert) is likely to be perceived later than auditory messages, the 

distances recommended above may have to be increased somewhat to account for this delay. Turning off the current

route is only one type of maneuver. Many other types (i.e., turning at a T-intersection, or an existing freeway)

should be studied separately to determine which factors will affect them. The results of these studies could then be

combined with the above guidelines to determine the appropriate timings for any possible type of combination of

maneuvers. 

In reference 3, it was recommended that if two maneuvers are less than 10 seconds apart, the two instructions should

be given together, before the first maneuver. This is referred to as “stacking” the messages. Reference 1 gave a 

similar recommendation, stating that when the distance between two subsequent maneuvers is less than the 

minimum preferred distance for that speed, the instructions should be stacked.

References:

1. Ross, T., Vaughan, G., and Nicolle, C. (1997). Design guidelines for route guidance systems: Development

process and an empirical example for timing of guidance instructions. In Y. I. Noy (Ed.), Ergonomics and

safety of intelligent driver interfaces (pp. 139-152). Mahwah, NJ: Lawrence Erlbaum Associates. 

2. Green, P., and George, K. (1995). When should auditory guidance systems tell drivers to turn? Proceedings of 

the Human Factors and Ergonomics Society 39th Annual Meeting, 1072-1076. 

3. Verwey, W. B., Alm, H., Groeger, J. A., Janssen, W. H., Kuiken, M. J., Schraagen, J. M., Schumann, J., van 

Winsum, W., and Wontorra, H. (1993). GIDS functions. In J. A. Michon (Ed.), Generic intelligent driver 

support: A comprehensive report on GIDS (pp. 113-144). London: Taylor and Francis. 

 6-21 
PERCEIVED ANNOYANCE OF AUDITORY SIGNALS

Introduction: Perceived annoyance of auditory signals refers to the subjective annoyance associated with particular 

signal characteristics. Although many sound parameters that increase urgency also increase annoyance careful 

design can create highly urgent sounds that are not overly annoying. The goal is to minimize the annoyance 

associated with a warning, balanced by the need to match the urgency of the signal to the urgency of the situation. 

This is called “annoyance tradeoff” and should be considered in signal design. 

Design Guidelines 

• For signals to be perceived as appropriate, highly urgent sounds should be used for highly critical situations. 

• For signals to be perceived as appropriate, low annoyance sounds should be used for benign situations. 

• Sound characteristics of pulse duration, burst density, sound type, and speed all increase perceived urgency

more than perceived annoyance. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 6-9. Sound Characteristics that Increase Urgency, While Having a Modest Effect on Annoyance

CHARACTERISTIC EFFECT ON URGENCY EFFECT ON ANNOYANCE

Duration of sound (Pulse) Longer >> more urgent Longer > more annoying 

Burst density High >> more urgent High > more annoying

Speed Faster >> more urgent Faster > more annoying 

E-mail Scenario

A= -1.05Urgency +119.6

R2 = 0.394

A = -1.55Annoyance +141.4

R2

 =0.6671

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Urgency/Annoyance

Rated Appropriateness

Annoyance Urgency Linear (Urgency) Linear (Annoyance)

Collision Avoidance Scenario

A= 0.27Annoyance +40.2

R2= 0.0937

A= 1.05Urgency +0.0238

R2= 0.892

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Annoyance/Urgency

Rated Appropriateness

Annoyance Urgency Linear (Annoyance) Linear (Urgency)

Collision Avoidance Scenario

A= 0.27Annoyance +40.2

R2= 0.0937

A= 1.05Urgency +0.0238

R2= 0.892

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Annoyance/Urgency

Rated Appropriateness

Annoyance Urgency Linear (Annoyance) Linear (Urgency)

E-mail Scenario

A= -1.05Urgency +119.6

R2 = 0.394

A = -1.55Annoyance +141.4

R2

 =0.6671

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Urgency/Annoyance

Rated Appropriateness

Annoyance Urgency Linear (Urgency) Linear (Annoyance)

Collision Avoidance Scenario

A= 0.27Annoyance +40.2

R2= 0.0937

A= 1.05Urgency +0.0238

R2= 0.892

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Annoyance/Urgency

Rated Appropriateness

Annoyance Urgency Linear (Annoyance) Linear (Urgency)

Collision Avoidance Scenario

A= 0.27Annoyance +40.2

R2= 0.0937

A= 1.05Urgency +0.0238

R2= 0.892

20

30

40

50

60

70

80

90

30 35 40 45 50 55 60 65 70 75 80

Rated Annoyance/Urgency

Rated Appropriateness

Annoyance Urgency Linear (Annoyance) Linear (Urgency)

Figure 6-5. Appropriateness Depends on Perceived Annoyance for Benign Situations (e.g., e-mail 

notification), Whereas Appropriateness Depends on Perceived Urgency for Highly Critical 

Situations (e.g., collision avoidance) 

 6-22 
Discussion: Substantial research has shown that sound parameters can effect perceived urgency (reference 1). The 

urgency mapping principle states that the urgency of the sound should a match the urgency of its referent. Like 

urgency, annoyance is systematically affected by sound parameters (references 2 and 3). Recently, research has 

shown that perceived annoyance of a sound is not completely dependent on the parameters that affect urgency

(reference 4). Some sound parameters, such as those listed in the table in the guideline, can increase urgency

substantially, while increasing annoyance relatively little. Using these parameters, it is possible to design a highly 

urgent sound that is less annoying than other sounds with the same perceived urgency. In general, design of highly

urgent signals involves a tradeoff between urgency and annoyance, but some sound parameters can help minimize 

the annoyance of highly urgent sounds. 

Recent results also show that the importance of annoyance is greater when designing sounds for benign alerts 

(reference 4). Perceived annoyance is a strong predictor of perceived appropriateness for auditory signals for benign

events, whereas perceived urgency is a strong predictor of perceived appropriateness for auditory signals for critical 

events. The figure in the guideline shows that this relationship is quite robust, with perceived annoyance accounting 

for 67 percent of the variance of perceived appropriateness for email alerts and only 9 percent of the variance for a 

collision avoidance warning. Conversely, perceived urgency accounts for almost 90 percent of the variance of 

perceived appropriateness of collision avoidance warnings. This relationships shows that designing to minimize 

annoyance can be as critical as designing to map urgency.

Design Issues: Sound perception and perceived urgency and annoyance are somewhat dependent on the context

and intended message of the signal (reference 5). This makes it critically important to evaluate the sounds generated

using these guidelines in the driving context. Even using imagined driving scenarios in a laboratory situation

affected the perceived urgency and annoyance of sounds (reference 4). In addition, urgency mapping and the 

annoyance tradeoff are only two considerations in creating useful auditory alerts. A critical consideration for a 

situation that contains multiple alerts is the ability of drivers to discriminate and recognize multiple auditory signals, 

as described earlier in the section Design of Complex Tones. 

Cross References: 

The Auditory Presentation of In-Vehicle Information, p. 6-1; Design of Complex Tones, p. 6-8; Perceived Urgency

of Auditory Signals, p. 6-16

References:

1. Edworthy, J., Loxley, S., and Dennis, I. (1991). Improving auditory warning design - Relationship between 

warning sound parameters and perceived urgency. Human Factors, 33(2), 205-231.

2. Laird, D. A., and Coye, K. (1929). Psychological measurements of annoyance related to pitch and loudness. 

Journal of the Acoustical Society of America, 1, 156-163. 

3. Berglund, B., and Preis, A. (1997). Is perceived annoyance more subject-dependent than perceived loudness?

Acoustica, 83(2), 313-319. 

4. Marshall, D., Lee, J D., and Austria, A. (2001). Annoyance and urgency of auditory alerts for in-vehicle 

information systems. Proceedings of the 45th Annual Meeting of the Human Factors and Ergonomics 

Society, 2, 1627-1631.

5. Edworthy, J., and Adams, A. (1996). Warning design: A research prospective. Bristol, PA: Taylor and 

Francis. 

 6-23 
CHAPTER 7: EVALUATING IN-VEHICLE ICONS

Overview of General Procedures for Evaluating In-Vehicle Icons............................................7-2 

Production Test...........................................................................................................................7-4 

Appropriateness Ranking Test....................................................................................................7-6

Comprehension/Recognition Test...............................................................................................7-8 

Matching Test ...........................................................................................................................7-10 

Additional Symbol Evaluation Approaches..............................................................................7-12 

 7-1
OVERVIEW OF GENERAL PROCEDURES FOR EVALUATING IN-VEHICLE ICONS 

Introduction: Evaluating icons refers to the general process of determining whether an icon, or an integrated set of

icons, meets specific criteria in areas such as legibility, recognition, interpretation, and driver preferences. 

Developing useful and effective icons requires evaluation. A rigorous and iterative evaluation phase in icon design

increases the likelihood that the implementation of the icon in the in-vehicle environment will improve driving and

system performance and not negatively impact driver safety. 

Design Guidelines 

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Poor

Response?

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Testing may be complete. 

Proceed as necessary.

Testing may be complete. 

Proceed as necessary.

Are candidate

icons developed

and/or in use?

(see chapter 8)

Poor

response?

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Comprehension/Recognition Tests 

(see page 7- 8)

• Prepare test materials

• Provide subjects with instruction

• Test candidate symbols with a representative

group of subjects

• Analyze data

• Interpret results

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Conduct Appropriateness Ranking Tests 

(see page 7-6)

• Reproduce Production Test icons

• Randomize presentation order to test icons

• Rank order test icons

• Calculate scale values

• Select candidates for further study

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Use Production Test to generate Ideas for Icon 

(see page 7-4)

• Identify messages for icons

• Generate candidate symbols/icons

• Evaluate candidate symbols/icons

• Identify candidate icons for further testing

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Testing may be complete. As necessary,

redesign icons and repeat evaluations.

Consider alternate approaches to evaluations

(see page 7-12).

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Conduct Matching Tests (see page 7-10)

• Prepare test materials

• Provide instructions to subjects

• Conduct test

• Analyze data

• Interpret results

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see chapter 3)

• Recognizability (see chapter 4)

• Interpretability (see chapter 5)

Testing may be complete. 

Proceed as necessary.

Testing may be complete. 

Proceed as necessary.

Are candidate

icons developed

and/or in use?

(see Chapter 8)

Poor

Response?

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Testing may be complete. 

Proceed as necessary.

Testing may be complete. 

Proceed as necessary.

Are candidate

icons developed

and/or in use?

(see chapter 8)

Poor

response?

Conduct Comprehension/Recognition Tests 

(see page 7 -8)

• Prepare Test Materials

• Provide Subjects with Instruction

• Test Candidate Symbols with a Representa -

tive Group of Subjects

• Analyze Data

• Interpret Results

Conduct Comprehension/Recognition Tests 

(see page 7- 8)

• Prepare test materials

• Provide subjects with instruction

• Test candidate symbols with a representative

group of subjects

• Analyze data

• Interpret results

Conduct Appropriateness Ranking Tests 

(see page 7 -6)

• Reproduce Production Test Icons

• Randomize Presentation Order to Test Icons

• Rank Order Test Icons

• Calculate Scale Values

• Select Candidates for Further Study

Conduct Appropriateness Ranking Tests 

(see page 7-6)

• Reproduce Production Test icons

• Randomize presentation order to test icons

• Rank order test icons

• Calculate scale values

• Select candidates for further study

Use Production Test to Generate Ideas for Icon

(see page 7 -4)

• Identify Messages for Icons

• Generate Candidate Symbols/Icons

• Evaluate Candidate Symbols/Icons

• Identify Candidate Icons for Further Testing

Use Production Test to generate Ideas for Icon 

(see page 7-4)

• Identify messages for icons

• Generate candidate symbols/icons

• Evaluate candidate symbols/icons

• Identify candidate icons for further testing

Testing may be complete. As necessary,

Re-design Icons and Repeat Evaluations.

Consider alternate approaches to evaluations

(see page 7 -12).

Testing may be complete. As necessary,

redesign icons and repeat evaluations.

Consider alternate approaches to evaluations

(see page 7-12).

Conduct Matching Tests (see page 7 -10)

• Prepare Test Materials

• Provide Instructions to Subjects

• Conduct Test

• Analyze Data

• Interpret Results

Conduct Matching Tests (see page 7-10)

• Prepare test materials

• Provide instructions to subjects

• Conduct test

• Analyze data

• Interpret results

Yes

No

No Yes

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see Chapter 3)

• Recognizability (see Chapter 4)

• Interpretability (see Chapter 5)

Conduct analyses to determine that the icons

conform to design principles and guidelines for:

• Legibility (see chapter 3)

• Recognizability (see chapter 4)

• Interpretability (see chapter 5)

Testing may be complete. 

Proceed as necessary.

Testing may be complete. 

Proceed as necessary.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 7-1. Overview of Procedures for Evaluating In-Vehicle Icons

 7-2
Discussion: General procedures for evaluating icons have been presented in a number of data sources, including 

references 1, 2, 3, and 4. Importantly, the procedures outlined in this chapter reflect an integrated approach to icon

evaluation. That is, each evaluation procedure (Production Test, Appropriateness Ranking Test, Comprehension/ 

Recognition Test, and Matching Test) addresses different research objectives and represents a key step in an overall 

process of developing legible, recognizable, and interpretable in-vehicle icons. 

Evaluations of individual icons may not require going through the entire evaluation process. For example, if the 

icon development team has 3-5 strong candidate icons in-hand for a particular message, then the Production Test

and the Appropriateness Ranking Test may not be needed. Similarly, if high levels of comprehension are obtained 

in the Comprehension/Recognition Test, then the Matching Test may not be needed. 

Reference 4 provides guidelines for the development and evaluation of hazard and safety symbols. Many of the 

guidelines contained in reference 4 for the graphic design of symbols are general, and the recommendations

provided for specific symbols are not for in-vehicle applications. However, some of the symbol evaluation 

procedures suggested in reference 4 are similar to those contained here. Some key differences between the 

guidelines presented here and those presented in reference 4 are: (1) Production Test is not called out as a formal 

procedure in reference 4; evaluations begin by selecting or gathering “existing symbol alternatives”; (2) An

Appropriateness Ranking procedure is also not specified; instead, a comprehension estimation procedure (in which

subjects estimate the percentage of the driving population that would understand a candidate icon ) is used to

eliminate poor candidates; (3) Criteria for acceptance following an open-ended Comprehension Test is 85 percent

(versus the ISO criteria of 66 percent), with a maximum of 5 percent critical confusions; and (4) a Matching Test is 

not discussed. 

While a subset of these evaluation procedures (as well as the alternate procedures described on pages 7-4 through 7-

13) may be used, the IVIS developer should be aware of the limitations inherent in such an approach. That is, key

issues associated with the effectiveness of a given icon may not be addressed without a complete, integrated 

approach to in-vehicle icon evaluation. 

Design Issues: All evaluations of in-vehicle icons should be performed using test subjects who are representative of 

the driving public. Key demographic variables include age and gender. Age effects, in particular, can be expected 

for icon evaluations. Thus, individual evaluations should use a mix of younger and older test subjects. Also,

representative non-English speakers should be included in testing. 

Cross References: 

General Development Process for In-Vehicle Icons, p. 2-2; Production Test, p. 7-4; Appropriateness Ranking 

Test, p. 7-6; Comprehension/Recognition Test, p. 7-8; Matching Test, p. 7-10; Additional Symbol Evaluation

Approaches, p. 7-12

References:

1. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby

and H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed material (pp. 

277-297). New York: J. Wiley & Sons. 

2. International Organization for Standardization (ISO)/DIS 9186. (1988). Procedures for the development and 

testing of public information symbols. Geneva, Switzerland: ISO. 

3. Collins, B. L. (1982). The development and evaluation of effective symbol signs. Washington, DC: U.S.

Department of Commerce (NBS Building Science Series, 141). 

4. American National Standards Institute. (1998). American national standard criteria for safety symbols, ANSI

Z535.3. Washington, DC: NEMA. 

 7-3
PRODUCTION TEST

Introduction: The production test refers to an icon evaluation approach in which a broad range of candidate

symbols for a concept or referent (i.e., in-vehicle message) are generated. It is used when no symbols for a given

message exist (reference 1). In this test, subjects are asked to draw symbols that they think represent a particular 

message. The output of the production test is a number of graphic or symbolic representations of a message that are

considered effective and comprehensible by individual subjects. The production test will not result in a final icon

selection. It is used to generate candidate symbols/icons only.

Design Guidelines 

Identify Messages

for Icons

Identify messages

for icons

• Select messages (functions, conditions, etc.) for which an in-vehicle icon is

needed and no standard icons or symbols are available.

Generate

Candidate

Symbols/Icons

Generate

candidate

symbols/icons

• Ask groups of designers and representative drivers to generate

candidate icons/symbols or verbal descriptions of icon requirements.

• Key goals include: using a wide and diverse range of subjects in the test;

identifying meaningful, simple, and understandable icons for the messages;

asking subjects to consider typical and comprehensible associations and

metaphors that come to mind when considering the message.

Evaluate Candidate

Symbols/Icons

Evaluate candidate

symbols/icons

• Key questions that can be used to guide the analysis include: Were any icons

or elements/features within icons consistently produced? Did different subject

groups (e.g., design engineers vs. real-world drivers) produce consistently

different images for the same message? Can these different images be

combined or reconciled in some way? Can the verbal descriptions the subjects

generated be used to develop new candidate icons?

Identify Candidate

Icons for Further

Testing

Identify candidate

icons for further

testing

• Use the icons and verbal descriptions that were produced earlier.

• Select a broad range of ideas.

• Drawings or ideas may be sorted into different categories based on

consistencies in image content.

• For each category of similar images, one or two images can be selected or

generated for additional tests.

• The production test will not result in a final icon selection. It is used to

generate candidate symbols/icons only.

Identify Messages

for Icons

Identify messages

for icons

• Select messages (functions, conditions, etc.) for which an in-vehicle icon is

needed and no standard icons or symbols are available.

Generate

Candidate

Symbols/Icons

Generate

candidate

symbols/icons

•

• Key goals include: using a wide and diverse range of subjects in the test;

identifying meaningful, simple, and understandable icons for the messages;

asking subjects to consider typical and comprehensible associations and

metaphors that come to mind when considering the message.

Evaluate Candidate

Symbols/Icons

Evaluate candidate

symbols/icons

•

Identify Candidate

Icons for Further

Testing

Identify candidate

icons for further

testing

• Use the icons and verbal descriptions that were produced earlier.

• Select a broad range of ideas.

•

consistencies in image content.

• For each category of similar images, one or two images can be selected or

generated for additional tests.

• The production test will not result in a final icon selection. It is used to

generate candidate symbols/icons only.

Identify Messages

for Icons

Identify messages

for icons

• Select messages (functions, conditions, etc.) for which an in-vehicle icon is

needed and no standard icons or symbols are available.

Generate

Candidate

Symbols/Icons

Generate

candidate

symbols/icons

• Ask groups of designers and representative drivers to generate

candidate icons/symbols or verbal descriptions of icon requirements.

• Key goals include: using a wide and diverse range of subjects in the test;

identifying meaningful, simple, and understandable icons for the messages;

asking subjects to consider typical and comprehensible associations and

metaphors that come to mind when considering the message.

Evaluate Candidate

Symbols/Icons

Evaluate candidate

symbols/icons

• Key questions that can be used to guide the analysis include: Were any icons

or elements/features within icons consistently produced? Did different subject

groups (e.g., design engineers vs. real-world drivers) produce consistently

different images for the same message? Can these different images be

combined or reconciled in some way? Can the verbal descriptions the subjects

generated be used to develop new candidate icons?

Identify Candidate

Icons for Further

Testing

Identify candidate

icons for further

testing

• Use the icons and verbal descriptions that were produced earlier.

• Select a broad range of ideas.

• Drawings or ideas may be sorted into different categories based on

consistencies in image content.

• For each category of similar images, one or two images can be selected or

generated for additional tests.

• The production test will not result in a final icon selection. It is used to

generate candidate symbols/icons only.

Identify Messages

for Icons

Identify messages

for icons

• Select messages (functions, conditions, etc.) for which an in-vehicle icon is

needed and no standard icons or symbols are available.

Generate

Candidate

Symbols/Icons

Generate

candidate

symbols/icons

•

• Key goals include: using a wide and diverse range of subjects in the test;

identifying meaningful, simple, and understandable icons for the messages;

asking subjects to consider typical and comprehensible associations and

metaphors that come to mind when considering the message.

Evaluate Candidate

Symbols/Icons

Evaluate candidate

symbols/icons

•

Identify Candidate

Icons for Further

Testing

Identify candidate

icons for further

testing

• Use the icons and verbal descriptions that were produced earlier.

• Select a broad range of ideas.

•

consistencies in image content.

• For each category of similar images, one or two images can be selected or

generated for additional tests.

• The production test will not result in a final icon selection. It is used to

generate candidate symbols/icons only.

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on 

Expert Judgment

Based Primarily on

Experimental Data

Figure 7-2. Production Test 

 7-4
Discussion: Empirical testing of candidate icons requires a variety of candidate symbols to present to subjects. The 

production test has been identified by reference 1 as a key step in icon development and an important means for

generating a wide range of images for subsequent testing. 

Reference 2 used a production test to generate ideas for symbols for common in-vehicle systems (coolant, fuel, air, 

oil, transmission, hydraulic, and brake), and specific conditions associated with the system (fluid level, temperature, 

pressure, and filter). This process generated a wide variety of candidate symbols. Importantly, variation across the 

symbols reflected characteristics of the subjects themselves. Some were serious, well thought out, and detailed;

others were humorous and less thoughtful. Many reflected the type of work performed by the subjects, such as the 

mechanistic and function-oriented drawings made by subjects who were engineers.

Design Issues: The production test is not, by itself, a sufficient means to validate icons or symbols. The overall

goal of the production test is to create a number of different candidate symbols as input for the more systematic

evaluation approaches such as the comprehension/recognition test. In addition, the production test relies on the 

participants’ ability to conceptualize the referent and generate an icon that includes the attributes of the referent

needed for a comprehensible icon. With complex or novel concepts, this may not be an efficient and effective 

process for icon development. 

An alternative is to use knowledge elicitation and concept mapping techniques to identify the elements of a 

comprehensible icon—that is, to conduct structured focus groups or one-on-one interviews with designers to elicit 

ideas about candidate icons. The objective of concept mapping, as applied to icon development, is to identify 

attributes of the referent that uniquely specify it and are commonly associated with it. Several structured processes

exist to support this activity (see references 3, 4, and 5). In general, these processes begin by identifying concepts

associated with a particular activity or system (e.g., in-vehicle routing and navigation). Once general concepts are 

identified, participants are queried to define distinguishing attributes and relationships. An example question might

be: “How would you describe this item?” Once attributes and their relationships have been defined, a series of

queries is used to refine them. Example questions might be: “Are there characteristics of this item that are not

included in the list?” or “What are the most relevant characteristics in identifying this item?” Attributes identified

by several users can be combined to define the features required to enhance icon comprehension. This process can

be performed by manually sorting and combining the participants’ responses, or by using sophisticated statistical 

techniques, such as factor and cluster analysis (see references 6 and 7). All evaluations of in-vehicle icons should be

performed using test subjects who are representative of the driving public. Key demographic variables include age 

and gender. Age effects, in particular, can be expected for icon evaluations. Thus, individual evaluations should use

a mix of younger and older test subjects. 

Cross References:

Overview of General Procedures for Evaluating In-Vehicle Icons, p. 7-2; Appropriateness Ranking Test, p. 7-6;

Comprehension/Recognition Test, p. 7-8; Matching Test, p. 7-10; Additional Symbol Evaluation Approaches, p. 7-12

References:

1. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby and H. Zwaga 

(Eds.), Information design: The design and evaluation of signs and printed material (pp. 277-297). New York: 

J. Wiley & Sons.

2. Green, P. (1981). Displays for automotive instrument panels: Production and rating of symbols. HSRI Research Review,

July-August, 1-12. 

3. Hart, A. (1986). Knowledge acquisition for expert systems. New York: McGraw-Hill. 

4. Joiner, C. (1998). Concept mapping in marketing: A research tool for uncovering consumers’ knowledge structure 

associations. Advances in Consumer Research, Vol. XXV, 311-317. 

5. McGraw, K., and Harbison, K. (1997). User-centered requirements: The scenario-based engineering process. Mahwah, NJ: 

Lawrence Erlbaum.

6. Shaw, M. (1981). Recent advances in personal construct technology. New York: Academic Press.

7. Wilson, J. R., and Corlett, E. N. (1990). Evaluation of human work. New York: Taylor and Francis.

 7-5
APPROPRIATENESS RANKING TEST

Introduction: The purpose of the appropriateness ranking test is to screen the candidate symbols generated during 

the production test and select the best for further testing. Essentially, subjects are asked to rank order a set of

candidate symbols for a message with respect to their relative appropriateness. Once these ranking data have been

gathered, the three candidate symbols with the highest ranking are typically selected for further testing.

Design Guidelines 

Re-produce

Production Test

Icons

Reproduce

Production Test

icons

• For each message being considered, produce a set of cards.

• Each card should show one of the candidate icons developed during the production test or identified using

other means.

Randomize

Presentation Order

of Test Icons

Randomize

presentation order

of test icons

• For each subject, randomize the set of cards containing the candidate icons prior to testing.

• If multiple messages are being tested (more than one set of cards) the order in which subjects rank order

each set of cards should be counterbalanced across subjects.

Rank Order Test

Icons

Rank order test

icons

• Ask representative subjects to sort the cards within each card set according to the degree to which each

candidate icon is perceived to be an appropriate one for the message under consideration (i.e., rank order

the cards within the set according to their appropriateness).

• The cards can be sorted by placing the card with the most appropriate icon first in the set and placing the

least appropriate icon last in the set.

• Multiple card sets can be used to test a group of subjects at the same time.

Calculate Scale

Values

Calculate scale

values

• Using an approach such as Torgerson’s Categorical Scaling Procedure (reference 3), calculate scale values

for each of the candidate icons.

• Tutorial 1 provides a step-by-step description of the calculations required to calculate scale values from rank

orders.

• This provides not only a general rank order, but also some indication as to how much the candidate symbols

differ along an interval scale.

Select Candidates

for Further Study

Select candidates

for further study

• Using the interval scale values, select approximately three candidates for each message for further study.

• Reference 1 provides the following criteria for selecting these candidates, “When differences between scale 

values are minimal, symbol variants with different image content are chosen, ignoring graphic detail.”

Thus, the “top three” candidates are not necessarily the ones chosen for further study.

• Other selection issues include the relative differences between the scale values and the uniqueness across

the candidates. Thus, in a close field of candidates (i.e., smaller differences in scale values), those

candidates with acceptable appropriateness ranks and some heterogeneity, in terms of icon/symbol features, 

might be selected.

• The appropriateness ranking test will not result in a final icon selection. It is used to provide a

preliminary evaluation of candidate symbols/icons only.

Re-produce

Production Test

Icons

Reproduce

production test

icons

• For each message being considered, produce a set of cards.

•

Randomize

Presentation Order

of Test Icons

Randomize

presentation order

of test icons

•

•

Rank Order Test

Icons

Rank order test

icons

•

•

•

Calculate Scale

Values

Calculate scale

values

•

for each of the candidate icons.

•

•

Select Candidates

for Further Study

Select candidates

for further study

•

•

•

•

Re-produce

Production Test

Icons

Reproduce

Production Test

icons

• For each message being considered, produce a set of cards.

• Each card should show one of the candidate icons developed during the production test or identified using

other means.

Randomize

Presentation Order

of Test Icons

Randomize

presentation order

of test icons

• For each subject, randomize the set of cards containing the candidate icons prior to testing.

• If multiple messages are being tested (more than one set of cards) the order in which subjects rank order

each set of cards should be counterbalanced across subjects.

Rank Order Test

Icons

Rank order test

icons

• Ask representative subjects to sort the cards within each card set according to the degree to which each

candidate icon is perceived to be an appropriate one for the message under consideration (i.e., rank order

the cards within the set according to their appropriateness).

• The cards can be sorted by placing the card with the most appropriate icon first in the set and placing the

least appropriate icon last in the set.

• Multiple card sets can be used to test a group of subjects at the same time.

Calculate Scale

Values

Calculate scale

values

• Using an approach such as Torgerson’s Categorical Scaling Procedure (reference 3), calculate scale values

for each of the candidate icons.

• Tutorial 1 provides a step-by-step description of the calculations required to calculate scale values from rank

orders.

• This provides not only a general rank order, but also some indication as to how much the candidate symbols

differ along an interval scale.

Select Candidates

for Further Study

Select candidates

for further study

• Using the interval scale values, select approximately three candidates for each message for further study.

• Reference 1 provides the following criteria for selecting these candidates, “When differences between scale 

values are minimal, symbol variants with different image content are chosen, ignoring graphic detail.”

Thus, the “top three” candidates are not necessarily the ones chosen for further study.

• Other selection issues include the relative differences between the scale values and the uniqueness across

the candidates. Thus, in a close field of candidates (i.e., smaller differences in scale values), those

candidates with acceptable appropriateness ranks and some heterogeneity, in terms of icon/symbol features, 

might be selected.

• The appropriateness ranking test will not result in a final icon selection. It is used to provide a

preliminary evaluation of candidate symbols/icons only.

Re-produce

Production Test

Icons

Reproduce

production test

icons

• For each message being considered, produce a set of cards.

•

Randomize

Presentation Order

of Test Icons

Randomize

presentation order

of test icons

•

•

Rank Order Test

Icons

Rank order test

icons

•

•

•

Calculate Scale

Values

Calculate scale

values

•

for each of the candidate icons.

•

•

Select Candidates

for Further Study

Select candidates

for further study

•

•

•

•

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 7-3. Appropriateness Ranking Test

 7-6
Discussion: A preliminary screening of candidate icons for a message is necessary to make further testing of the

icons feasible and cost-effective (see also reference 1). The appropriateness ranking test provides an objective, 

quick, low-cost approach to the task of reducing what can be a large number of candidate icons to a more 

manageable number of high-potential candidates. 

The appropriateness ranking test has been successfully used in previous symbol development efforts. For example, 

in reference 2, six messages were tested using the procedure described above, with between eight and 35 candidate

symbols being rank ordered for each message. In this study, the results of the appropriateness ranking test allowed 

the researchers to reduce, in a systematic manner, the number of these candidates to about three per message. 

The advantage of converting rank order data to an interval scale of perceived appropriateness is that rank orders 

alone do not indicate the relative differences among judged stimuli. Thus, mean ranks suggest that differences in

perceived appropriateness between, for example, stimuli 1 and 2 are the same as differences between stimuli 2 and 

3. The Categorical Scaling Procedure provides the interval data necessary to make informed decisions regarding the 

true relative appropriateness of candidate icons. 

Design Issues: When developing candidate icons for the test, consider that driver perception and performance will 

vary as a function of the medium used to present the test stimuli. That is, display parameters such as resolution,

production of color, and luminance can affect responses. In general, the color, brightness, resolution, and size of test

icons should be as close as possible to how the icons will be viewed by drivers in the in-vehicle environment. 

As noted in reference 4, the appropriateness ranking test should not be used to make final selections of icons. 

Considerable experimental data suggest that more detailed, concrete icons are consistently judged to be more 

appropriate and given higher ranks than more abstract icons. However, highly detailed icons may lead to increased

response times, are more easily confused with other icons, and are not always consistent with the need to provide 

simple visual information through in-vehicle displays. Thus, the appropriateness ranking test helps to identify 

candidate icons based on image content only, and cannot address more complex issues such as the comprehensibility 

of icons in an operational environment.

Often, subjects will be unable to distinguish the appropriateness of a given icon from another. Subjects should be

instructed that the same ranking (or a tie) can be given to more than one candidate icon. All evaluations of invehicle icons should be performed using test subjects who are representative of the driving public. Key

demographic variables include age and gender. Age effects, in particular, can be expected for icon evaluations. 

Thus, individual evaluations should use a mix of younger and older test subjects.

Cross References:

Overview of General Procedures for Evaluating In-Vehicle Icons, p. 7-2; Production Test, p. 7-4;

Comprehension/Recognition Test, p. 7-8; Matching Test, p. 7-10; Additional Symbol Evaluation 

Approaches, p. 7-12; Tutorials: Analysis of Rank Order Data, p. 9-1 

References:

1. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby & 

H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed material (pp. 277-

297). New York: J. Wiley & Sons. 

2. Easterby, R. S., and Zwaga, H. (1976). Evaluation of public information symbols, ISO tests: 1975 series (Report 

AP 60). Birmingham, UK: Applied Psychology Department, University of Aston at Birmingham.

3. Torgerson, W. S. (1965). Theory and methods of scaling. New York: J. Wiley & Sons. 

4. Hakiel, S. R. (1991). Evaluating icons for human-computer interfaces (Report No. HF 144). Hursley Park, 

Winchester, UK: IBM UK Laboratories Ltd.

 7-7
COMPREHENSION/RECOGNITION TEST

Introduction: The comprehension/recognition test refers to an evaluation technique that provides a means to

determine which of a number of candidate icons/symbols for a concept are best understood by a sample of subjects 

who represent the user population. During this test, an icon/symbol is presented to subjects, the context of the 

icon/symbol is specified (i.e., where they might expect to see the icon, according to reference 1), and subjects are 

asked to name the object, location, or activity associated with the icon/symbol. 

Design Guidelines 

Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test Candidate

Symbols with a

Representative

Group of Subjects

Prepare Test

Materials

Prepare Test

Materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide Subjects

with Instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze Data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

scheme: 1 = response matches intended meaning exactly; 2 = response captures key informational elements

intended meaning, but misses one or more key elements; 4 = response does not match intended meaning

but captures one or more key informational elements; 5 = response does not match intended meaning, but is

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret Results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test candidate

symbols with a

representative

group of subjects

Prepare Test

Materials

Prepare test

materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide subjects

with instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test Candidate

Symbols with a

Representative

Group of Subjects

Prepare Test

Materials

Prepare Test

Materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide Subjects

with Instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze Data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret Results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test candidate

symbols with a

representative

group of subjects

Prepare Test

Materials

Prepare test

materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide subjects

with instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol.

of intended meaning, but misses one or more minor elements; 3 = response captures some aspects of

Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test Candidate

Symbols with a

Representative

Group of Subjects

Prepare Test

Materials

Prepare Test

Materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide Subjects

with Instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze Data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

scheme: 1 = response matches intended meaning exactly; 2 = response captures key informational elements

intended meaning, but misses one or more key elements; 4 = response does not match intended meaning

but captures one or more key informational elements; 5 = response does not match intended meaning, but is

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret Results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test candidate

symbols with a

representative

group of subjects

Prepare Test

Materials

Prepare test

materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide subjects

with instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test Candidate

Symbols with a

Representative

Group of Subjects

Prepare Test

Materials

Prepare Test

Materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide Subjects

with Instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze Data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret Results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol. Test Candidate

Symbols with a 

Representative 

Group of Subjects

Test candidate

symbols with a

representative

group of subjects

Prepare Test

Materials

Prepare test

materials

• Place candidate symbols on separate sheets of paper, slides, or computer screens, depending on the

presentation method planned for the study.

• Randomize presentation order across subjects.

• Separate different candidates for the same message into distinct test sets.

• Prepare and provide to subjects an example sheet with a common icon (like a fuel pump to indicate a

fuel gage) and its meaning written beneath the graphic.

Provide Subjects

with Instruction

Provide subjects

with instruction

• Indicate the context in which the icon will be used, either verbally or co-located with the icon.

• Subjects are to write down the action, condition, activity, location, etc. associated with the icon (e.g.,

“What do you think this icon means?”).

Analyze Data Analyze data

• Have a panel of judges independently categorize responses along a scale according to well-defined criteria that

identify the likelihood that an individual response indicates correct comprehension of the icon. That is, the 

perceived meaning should be compared to the intended meaning. For example, use an 8-category rating

but captures one or more key informational elements; 5 = 

somewhat relevant; 6 = subject’s response is in no way relevant to the intended meaning; 7 = subject indicates

no understanding of the icon; 8 = no answer.

• For each candidate, convert the total number of responses in each category into percentages.

Interpret Results Interpret results

• Decisions regarding minimum percent correct rates for individual icons should reflect designer’s needs,

as well as the consequences associated with selecting a cutoff that is too high or too low. Reference 2 

notes that ISO requirements for an acceptable symbol have, in the past, been a (minimum) 67 percent 

correct comprehension level (i.e., combined categories 1 and 2 from above).

• Present test subjects with candidate icons/symbols and ask them to write down the action, condition, 

activity, location, etc. that they believe is represented by the icon/symbol.

of intended meaning, but misses one or more minor elements; 3 = response captures some aspects of

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 7-4. Comprehension/Recognition Test 

 7-8
Discussion: Reference 1 has been developed as a standard procedure for developing and testing public information 

symbols. This standard provides a highly detailed set of instructions for testing symbols. Some computational

procedures in reference 1, however, are unnecessarily complex and the guidelines presented on the preceding page

represent a summary of the procedures listed in references 1 and 3. 

Design Issues: When developing candidate icons for the test, consider how driver perception and performance will 

vary as a function of the medium used to present the test stimuli. That is, display parameters such as resolution,

production of color, and luminance can affect responses. In general, the color, brightness, resolution, and size of test

icons should be as close as possible to how the icons will be viewed by drivers in the in-vehicle environment. 

All evaluations of in-vehicle icons should be performed using test subjects that are representative of the driving 

public. Key demographic variables include age and gender. Previous studies have indicated that significant

differences exist between younger people and older people in their ability to comprehend symbols (references 4 and

5). Therefore, subjects should be representative of the user population (e.g., half between the ages of 18 and 40 and 

the other half over 55 years). 

In real-world driving, icons are presented in the context of certain in-vehicle capabilities and driving circumstances. 

As such, evaluations of in-vehicle icons should include a description of the context in which icons will be presented

and used. However, icon evaluations should avoid providing either too little or too much context to experimental 

subjects. If too little context is provided, unrealistically low comprehension scores may result from subjects’ being

unable to connect a visual icon with its many possible meanings. Too much context may yield unrealistically high 

comprehension scores because the subjects have been cued for a certain response by the specificity of the context. 

Both extremes should be avoided. In chapter 9, a tutorial entitled “Providing Subjects with Context During Icon

Evaluations” provides both procedures and examples associated with providing appropriate context to experimental 

subjects. 

Candidate icons should be tested individually, as the focus is on testing absolute comprehension/recognition for 

individual icons. The goal is not to test confusability across icons (as it is in the matching test). 

Cross References:

Overview of General Procedures for Evaluating In-Vehicle Icons, p. 7-2; Production Test, p. 7-4; Appropriateness

Ranking Test, p. 7-6; Matching Test, p. 7-10; Additional Symbol Evaluation Approaches, p. 7-12; 

Tutorials: Providing Subjects with Context During Icon Evaluations, p. 9-11

References:

1. ISO/DIS 9186. (1988). Procedures for the development and testing of public information symbols. Geneva, 

Switzerland: ISO. 

2. Wolff, J. S., and Wogalter, M. S. (1998). Comprehension of pictorial symbols: Effect of context and test

method. Human Factors, 40(2), 173-186. 

3. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby

and H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed material (pp. 

277-297). New York: J. Wiley & Sons. 

4. Dewar, R. E., Kline, D. W., and Swanson, A. H. (1994). Age differences in comprehension of traffic sign

symbols. Transportation Research Record 1456, 1-10. 

5. Saunby, C. S., Farber, E. I., and DeMello, J. (1988). Driver understanding and recognition of automotive ISO 

symbols. SAE Technical Paper Series (No. 880056). Warrendale, PA: Society of Automotive Engineers. 

 7-9
MATCHING TEST

Introduction: After the best or most appropriate design for a symbol has been determined, it is important to

examine how well that symbol will work within a set and whether the many symbols within the set, can be

discriminated from one another without confusion. To do this, a Matching Test is performed. Subjects are shown a 

sheet with all of the symbols from a set on it, arranged in a matrix, and told the context under which they would use 

these symbols. Next, subjects are given a referent name and asked to indicate on the matrix which one of the

symbols stands for that particular referent. The outcome of the matching test is two measures of symbol

effectiveness: the number of correct choices of a particular symbol, and the degree of confusion among symbols 

Design Guidelines 

Prepare Test

Materials

Prepare test

materials

• Based on the results of a comprehension/recognition (or comparable test), select or create a

symbol for each message within a message set.

• Place the complete set of symbols, for a function or group of related functions, in a matrix on a

sheet of paper, slide, or computer screen. Between 4-8 symbols should be included in each

matrix.

• The medium selected for information presentation (i.e., paper, slide, or computer screen) should

be consistent with the expected in-vehicle conditions with respect to parameters such as

resolution, color, luminance, contrast, and size.

• Repeat for additional function or groups of icons.

• Randomize presentation order of symbol sets across subjects.

Provide Instructions

to Subjects

Provide instructions

to subjects

• Tell subjects the context in which the symbol set will be used, being careful that such

information does not create any bias.

• The subjects’ task will be to select the icon that best represents a particular driver message.

Analyze Data Analyze data

• Calculate the percentage of correct responses for each symbol/me

• Construct a confusion matrix with icons in the set as columns and messages and rows, data in

the cells should reflect the frequency with which an individualsymbol was matched with a

message.

Interpret Results Interpret results

• Use the percentage correct for each icon, as well as the confusions across icons, to develop

ideas for new icons or for the redesign of easily confusable

Conduct Test Conduct test

• Give the subject the meaning (or driver message) associated with one of the icons in the symbol

set and ask them to indicate which of the icons in the matrix represents that meaning.

• Repeat test procedure with additional symbol sets.

• To maintain independent choices, individual subjects can only be tested on one icon per symbol

set. Thus, while individual tests require little time, many sub

used up to 400 subjects per symbol).

Prepare Test

Materials

Prepare test

materials

•

symbol for each message within a message set.

•

sheet of paper, slide, or computer screen. Between 4-8 symbols should be included in each

matrix.

• The medium selected for information presentation (i.e., paper, slide, or computer screen) should

be consistent with the expected in-vehicle conditions with respect to parameters such as

resolution, color, luminance, contrast, and size.

• Repeat for additional function or groups of icons.

• Randomize presentation order of symbol sets across subjects.

Provide Instructions

to Subjects

Provide instructions

to subjects

• Tell subjects the context in which the symbol set will be used, being careful that such

information does not create any bias.

• The subjects’

Analyze Data Analyze data

• Calculate the percentage of correct responses for each symbol/message combination.

• Construct a confusion matrix with icons in the set as columns and messages and rows, data in

the cells should reflect the frequency with which an individualsymbol was matched with a

message.

Interpret Results Interpret results

•

ideas for new icons or for the redesign of easily confusable icons.

Conduct Test Conduct test

• Give the subject the meaning (or driver message) associated with one of the icons in the symbol

set and ask them to indicate which of the icons in the matrix represents that meaning.

• Repeat test procedure with additional symbol sets.

• To maintain independent choices, individual subjects can only be tested on one icon per symbol

set. Thus, while individual tests require little time, many subjects are required (reference 1

used up to 400 subjects per symbol).

Prepare Test

Materials

Prepare test

materials

• Based on the results of a comprehension/recognition (or comparable test), select or create a

symbol for each message within a message set.

• Place the complete set of symbols, for a function or group of related functions, in a matrix on a

sheet of paper, slide, or computer screen. Between 4-8 symbols should be included in each

matrix.

• The medium selected for information presentation (i.e., paper, slide, or computer screen) should

be consistent with the expected in-vehicle conditions with respect to parameters such as

resolution, color, luminance, contrast, and size.

• Repeat for additional function or groups of icons.

• Randomize presentation order of symbol sets across subjects.

Provide Instructions

to Subjects

Provide instructions

to subjects

• Tell subjects the context in which the symbol set will be used, being careful that such

information does not create any bias.

• The subjects’ task will be to select the icon that best represents a particular driver message.

Analyze Data Analyze data

• Calculate the percentage of correct responses for each symbol/me

• Construct a confusion matrix with icons in the set as columns and messages and rows, data in

the cells should reflect the frequency with which an individualsymbol was matched with a

message.

Interpret Results Interpret results

• Use the percentage correct for each icon, as well as the confusions across icons, to develop

ideas for new icons or for the redesign of easily confusable

Conduct Test Conduct test

• Give the subject the meaning (or driver message) associated with one of the icons in the symbol

set and ask them to indicate which of the icons in the matrix represents that meaning.

• Repeat test procedure with additional symbol sets.

• To maintain independent choices, individual subjects can only be tested on one icon per symbol

set. Thus, while individual tests require little time, many sub

used up to 400 subjects per symbol).

Prepare Test

Materials

Prepare test

materials

•

symbol for each message within a message set.

•

sheet of paper, slide, or computer screen. Between 4-8 symbols should be included in each

matrix.

• The medium selected for information presentation (i.e., paper, slide, or computer screen) should

be consistent with the expected in-vehicle conditions with respect to parameters such as

resolution, color, luminance, contrast, and size.

• Repeat for additional function or groups of icons.

• Randomize presentation order of symbol sets across subjects.

Provide Instructions

to Subjects

Provide instructions

to subjects

• Tell subjects the context in which the symbol set will be used, being careful that such

information does not create any bias.

• The subjects’

Analyze Data Analyze data

• Calculate the percentage of correct responses for each symbol/message combination.

• Construct a confusion matrix with icons in the set as columns and messages and rows, data in

the cells should reflect the frequency with which an individualsymbol was matched with a

message.

Interpret Results Interpret results

•

ideas for new icons or for the redesign of easily confusable icons.

Conduct Test Conduct test

• Give the subject the meaning (or driver message) associated with one of the icons in the symbol

set and ask them to indicate which of the icons in the matrix represents that meaning.

• Repeat test procedure with additional symbol sets.

• To maintain independent choices, individual subjects can only be tested on one icon per symbol

set. Thus, while individual tests require little time, many subjects are required (reference 1

used up to 400 subjects per symbol).

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Figure 7-5. Matching Test 

 7-10 
Discussion: The Matching Test measures the specific association between the content of an icon and an in-vehicle 

message when the icon is presented to a subject at the same time as other icons within an icon set (see also reference

1). Subjects are only tested on one icon per symbol set to avoid non-independence of their choices. If multiple 

icons within a symbol set were tested, individual choices would be dependent on previous choices, thus confounding 

the results. 

Data from the Matching Test can be represented in two ways. First, indicate the number of correct choices for a 

particular symbol by calculating the percentage of correct responses for each symbol/message combination. Second, 

construct a table with icons in the set as columns and messages as rows. Cell entries can show overall percentages 

associated with the subjects responses. Thus, incorrect as well as correct responses are depicted in the table (also

called a confusion matrix). 

If the scores from the Matching Test are acceptable to the design team, the testing may be complete. However, if 

some scores are too low, additional icon development and evaluation may be needed. 

Design Issues: When developing candidate icons for the test, consider that driver perception and performance will 

vary as a function of the medium used to present the test stimuli. That is, display parameters such as resolution,

production of color, and luminance can affect responses. In general, the color, brightness, resolution, and size of test

icons should be as close as possible to how the icons will be viewed by drivers in the in-vehicle environment. 

Importantly, the Matching Test does not measure any absolute trait of individual symbols, nor measure absolute 

comprehension or recognition associated with a candidate icon. All measures relate to subjects’ ability to match an

icon with a message within the context of other related icons. In this regard, icon developers often wish to develop

families or groups of icons that share some common purpose or meaning (e.g., collision avoidance). Groups or 

families of icons typically share some common design element such as color, border, size, or graphic style. The 

Matching Test may provide an ideal method for evaluating subjects’ ability to discriminate between related and

nonrelated icons. 

In real-world driving, icons are presented in the context of certain in-vehicle capabilities and driving circumstances. 

As such, evaluations of in-vehicle icons should include a description of the context in which they will be presented

and used. However, icon evaluations should avoid providing either too little or too much context to experimental 

subjects. If too little context is provided, unrealistically low comprehension scores may result from subjects’ being

unable to connect a visual icon with the many possible icon meanings. If too much context is provided,

unrealistically high comprehension scores may result because the subjects have been cued for a certain response by

the specificity of the context. Both extremes should be avoided. In chapter 9, a tutorial provides both procedures 

and examples associated with providing appropriate context to experimental subjects. 

Cross References:

Overview of General Procedures for Evaluating In-Vehicle Icons, p. 7-2; Production Test, p. 7-4; Appropriateness

Ranking Test, p. 7-6; Comprehension/Recognition Test, p. 7-8; Additional Symbol Evaluation Approaches, p. 7-12;

Tutorials: Providing Subjects with Context During Icon Evaluations, p. 9-11

References:

1. Zwaga, H., and Easterby, R. S. (1984). Developing effective symbols for public information. In R. Easterby

and H. Zwaga (Eds.), Information design: The design and evaluation of signs and printed material (pp. 

277-297). New York: J. Wiley & Sons. 

 7-11 
ADDITIONAL SYMBOL EVALUATION APPROACHES

Introduction: In addition to the evaluation approaches described in the previous guidelines in this chapter, a 

number of additional approaches have been suggested and successfully used to evaluate the effectiveness of icons.

Design Guidelines 

• The evaluation technique selected to assess the effectiveness of candidate icons should be consistent with the

goals and constraints of a particular system development effort. The table below summarizes a range of

alternative evaluation approaches, gives the advantages and disadvantages associated with each, and provides 

references for designers to go to for more detailed information. 

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Based Equally on Expert Judgment

and Experimental Data

Based Primarily on

Expert Judgment

Based Primarily on

Experimental Data

Table 7-1. Summary of Additional Symbol Evaluation Approaches 

Evaluation 

Technique Description Advantage/Disadvantage References

Rating task Subjects are asked to determine the degree 

to which a symbol suggests or

communicates its designated name. 

Reference 1 found that results of the rating 

task were well correlated with the results of 

the reaction time task (see below); however, 

ratings are easier to obtain and more 

statistically efficient. 

Reference 1 

Reaction time 

task (speed of 

comprehension)

Subjects are given a referent, then shown a 

slide of one of the symbols and asked to

indicate whether the referent and the symbol

are the “same.” The amount of time taken

to make the response is recorded as reaction 

time. 

Reaction time in a discrimination task is 

influenced by individual differences and

decreases markedly with learning (reference 

1). 

Reference 1 

Reference 2 

Identification

time task 

Subjects are shown slides of traffic signs (in 

both text and symbol format) and are asked

to identify verbally the message that is 

being presented. Their response time is 

recorded as identification time. 

Relatively inexpensive and easy means for 

obtaining information about the adequacy of 

symbols. 

Reference 3 

Reference 4 

Semantic 

differential 

method 

Subjects rate symbols on 12 different 

adjective pairs, such as weak-strong, 

strange-familiar. A factor analysis is then 

performed to evaluate the results. 

The factors included: evaluative, potency,

activity, and understandability. For all but 

understandability, it is difficult to determine 

the design issues that are associated with the 

factors.

Reference 5 

Reference 6 

Modified 

semantic 

differential 

method 

This method uses adjective pairs that are 

more specific and relevant to designers, 

such as balanced-unbalanced, confusingclear, etc. 

Reference 5 compared this method with 

traditional but logistically expensive 

measures, such as reaction time and glance

legibility, and found this technique to

provide a simple, inexpensive, and valid 

measure of comprehension. 

Reference 7 

 7-12 
Discussion: In many icon and in-vehicle display development efforts, there is insufficient time or budget available 

to conduct the sequential, inter-dependent series of evaluations described in the preceding design guidelines. This 

design guideline, therefore, identifies additional evaluation techniques that have been used and described in the 

human factors and icon development literature. 

Design Issues: The selection of an appropriate evaluation approach should reflect specific empirical objectives, as 

well as the driver messages, expected driving context, and design constraints associated with individual in-vehicle

icons or symbols. For example, if human response times to a particular icon are important for its effectiveness, then

evaluation should include dependent measures that will capture this information. In this particular case, the optimal 

icons will be those that satisfy icon comprehension and discrimination with the shortest response time. The 

evaluation of other icons or sets of icons may focus more on different types of measures and thus will require a 

completely different type of evaluation process. 

All evaluations of in-vehicle icons should be performed using test subjects who are representative of the driving 

public. Key demographic variables include age and gender. Age effects, in particular, can be expected for icon 

evaluations. Thus, individual evaluations should use a mix of younger and older test subjects. 

Cross References:

Overview of General Procedures for Evaluating In-Vehicle Icons, p. 7-2; Production Test, p. 7-4; Appropriateness

Ranking Test, p. 7-6; Comprehension/Recognition Test, p. 7-8; Matching Test, p. 7-10

References:

1. Green, P., and Pew, R. W. (1978). Evaluating pictographic symbols: An automotive application. Human

Factors, 20(1), 103-114.

2. Ells, J. G., and Dewar R. E. (1979). Rapid comprehension of verbal and symbolic traffic sign messages. Human

Factors, 21(2), 161-168.

3. Dewar, R. E., and Ells J. G. (1974). Comparison of three methods for evaluating traffic signs. Transportation 

Research Record, 503, 38-47. 

4. Dewar, R. E., Ells, J. G., and Mundy G. (1976). Reaction time as an index of traffic sign perception. Human

Factors, 18(4), 381-392.

5. Dewar, R. E., and Ells, J. G. (1977). The semantic differential as an index of traffic sign perception and 

comprehension. Human Factors, 19(2), 183-189.

6. Caron, J. P, Jamieson, D. G., and Dewar, R. E. (1980). Evaluating pictographs using semantic differential and 

classification techniques. Ergonomics, 23(2), 137-146.

7. Vora, P., Helander, M., Swede, H., and Wilson, J. (1991). Developing guidelines for symbol design: A

comparison of evaluation methodologies. Interface ‘91, 6-11 

 7-13 
CHAPTER 8: ICON COLLECTION 

Introduction: Generating new icons is a time-consuming and error-prone task. Designers can save time and 

develop more effective icons if they can draw upon proven icon designs rather than create new ones. Unfortunately, 

icons for in-vehicle systems are not collected in a single location, but are dispersed over the internet, held in

proprietary collections, and sold in large clip art collections. In addition, these icon sources are not organized in a 

way that can be easily matched to the functions and features of in-vehicle information systems. The Icon Collection

seeks to overcome these difficulties by providing designers with a set of candidate icons organized according to the 

functions and characteristics of in-vehicle information systems. 

The ideal situation would be one where a designer could simply take set of messages associated with an in-vehicle

function and look up that function in the Icon Collection to identify the appropriate icon. Unfortunately, this is not 

possible. Many messages do not have icons associated with them, so new icons must be designed. Also, many

candidate icons are obviously poor; existing icons may be useful only as bad examples or as inspiration for new

designs. Over time, additional icons will be developed for more in-vehicle systems and the Icon Collection can be

expanded; however, it will never offer a complete solution to the designer. The characteristics of a “good” icon

depend on the particular system and implementation. The collection provides designers with a well-organized 

collection of “good” and ”bad” candidate icons that can inspire them and reduce development time. 

The Icon Collection is organized according to the functions of in-vehicle systems. Functions such as routing and

navigation are composed of subfunctions such as trip planning and route guidance. Each subfunction may have

several messages, such as “price ranges for lodging along route” and “total trip time” for the subfunction of trip

planning. The table below lists the functions and subfunctions that describe in-vehicle information systems along 

with the page number associated with each function. 

Categories of Icons Included in this Collection 

Augmented Signage Page 8-3

Roadway notification sign information

Roadway regulatory sign information

Automated/Adaptive Cruise Control Page 8-5

Collision Avoidance Information Page 8-5

Braking devices 

Collision avoidance, general 

Forward collision avoidance 

Rear-end collision avoidance 

Road departure 

Side collision avoidance 

System status 

Commercial Vehicle Operations Information Page 8-10

Augmented signage information 

Cargo and vehicle monitoring information 

Trip planning 

General Navigation System Information Page 8-12

GPS status information 

Motorist Services Information Page 8-12

Broadcast service/attractions 

Destination coordination 

Email, messaging 

Entertainment 

Internet access

Message transfer 

Routing and Navigation Page 8-34

Route guidance

Route navigation 

Travel coordination and planning

Trip planning 

Safety and Warning Information Page 8-40

Airbag status/information 

Automatic/manual aid request 

Immediate hazard warning 

Parking aids 

Road condition information

Vehicle condition monitoring 

Weather information 

 8-1
For each message, the Icon Collection shows the source, an icon that matches the message, and comments regarding

the source of the icon. For example, the extract below shows an icon for the message “Lodging” for trip planning. 

In some cases, the symbol was edited in some manner to make it more relevant to the referrent (e.g., text may have 

been added or symbols combined) and this is indicated in the “Notes” area. 

ID#: 382 

Message: Lodging 

Source: Teague 

Notes:

File: Lodging.jpg 

The icons in the Icon Collection come from six sources: (1) the Internet, (2) commercially available clip art (e.g., 

Corel®), (3) noncommercial picture files available on the contractor’s intranet (cited as “Clickart”), (4) the 

automotive electronics industry, (5) past and present research and development efforts in the area of driver 

information (example sources include: ISO, “Drawn” (drawn by the contractor), SODS (a project conducted for the 

National Highway Traffic Safety Administration (NHTSA) in 1995), and the MUTCD), and (6) Teague (an 

industrial design firm under subcontract to the contractor during this project). 

 8-2
Icon Details by Icon Type

Augmented Signage

Roadway notification sign information

General

Function:

ID #: 119

Message: Added lane sign

File: 2 up arrows.jpg

Source: http://members.aol.com/rcmo

eur/w4.html

Notes:

ID #: 264

Message: Divided highway (road) sign

File: 2 opposite arrows.jpg

Source: http://members.arttoday.com/

Notes: twolane06bw.jpg

ID #: 96

Message: Drawbridge

File: drawbridge.gif

Source: http://members.arttoday.com/

Notes: drawbridge01bw.jpg, edited

ID #: 354

Message: Lane reduction transition 

sign

File: 2 lines.jpg

Source: http://members.aol.com/rcmo

eur/w4.html

Notes:

ID #: 262

Message: Merge sign

File: split arrow.jpg

Source: http://members.aol.com/rcmo

eur/w4.html

Notes:

Augmented Signage

Roadway notification sign information

General

Function:

ID #: 271

Message: Pedestrian crossing ahead

File: man.gif

Source: http://members.aol.com/rcmo

eur/rg.html

Notes:

ID #: 65

Message: Percent of grade

File: hill.jpg

Source: Corel ®

Notes:

ID #: 366

Message: Railroad crossing

File: double R.jpg

Source: http://members.aol.com/rcmo

eur/rrsign.html

Notes:

ID #: 42

Message: Sharp curve ahead

File: right arrow-text.jpg

Source: http://www.dps.state.ak.us/dm

v/DLMANUAL/pg44c.htm; 

http://members.aol.com/rcmo

eur/w1.html

Notes:

ID #: 14

Message: Steep downgrade

File: truck on slope.jpg

Source: http://members.aol.com/rcmo

eur/w7.html

Notes:

8-3
Icon Details by Icon Type

Augmented Signage

Roadway notification sign information

General

Function:

ID #: 183

Message: Tight ramp or intersection

File: curved arrow.jpg

Source: http://members.aol.com/rcmo

eur/w1.html

Notes:

ID #: 351

Message: Turn signs

File: right arrow.jpg

Source: http://members.aol.com/rcmo

eur/w1.html

Notes:

ID #: 139

Message: Winding road sign

File: squiggly arrow.jpg

Source: http://members.aol.com/rcmo

eur/w1.html

Notes:

Augmented Signage

Roadway regulatory sign information

General

Function:

ID #: 104

Message: No trucks

File: NoTruck.jpg

Source: http://members.arttoday.com/

Notes: notrucks01bw.jpg

ID #: 87

Message: Rock spray

File: rockspray.gif

Source: http://members.arttoday.com/

Notes: gravel04c.jpg, edited

Augmented Signage

Roadway regulatory sign information

General

Function:

ID #: 414

Message: Speed limit 50

File: SL 50.jpg

Source: http://www.dps.state.ak.us/dm

v/DLMANUAL/pg429.htm

Notes:

ID #: 268

Message: Stop ahead

File: stop arrow.jpg

Source: http://members.aol.com/rcmo

eur/w3.html

Notes:

ID #: 228

Message: Yield

File: yield.jpg

Source: Corel ®

Notes:

ID #: 176

Message: Yield ahead

File: yield arrow.jpg

Source: http://members.aol.com/rcmo

eur/r1.html

Notes:

8-4
Icon Details by Icon Type

Automated/Adaptive Cruise Control 

Devices

Automated/adaptive cruise control

General

Function:

ID #: 195

Message: Adaptive cruise control 

engaged

File: AutomatedCruiseControl8A-1.jpg

Source: ISO

Notes:

ID #: 216

Message: Adaptive cruise control 

engaged

File: GapWarn1.gif

Source: Industry

Notes:

ID #: 31

Message: Adaptive cruise control 

engaged

File: GapWarn3.gif

Source: Industry

Notes:

ID #: 8

Message: Adaptive cruise control 

failure

File: AutomatedCruiseControl8A-2.jpg

Source: ISO

Notes:

ID #: 114

Message: Adaptive cruise control not 

engaged

File: GapWarn2.gif

Source: Industry

Notes:

Automated/Adaptive Cruise Control 

Devices

Automated/adaptive cruise control

General

Function:

ID #: 393

Message: Adaptive cruise control not 

engaged

File: GapWarn4.gif

Source: Industry

Notes:

Collision Avoidance Information

Braking devices

General

Function:

ID #: 206

Message: Brake service required

File: Brake warning.jpg

Source: Teague

Notes:

ID #: 68

Message: Brake service required

File: Warning brakes.jpg

Source: Teague

Notes:

Collision Avoidance Information

Collision avoidance

General

Function:

ID #: 341

Message: Imminent collision warning

File: crash.jpg

Source: Teague

Notes:

8-5
Icon Details by Icon Type

Collision Avoidance Information

Collision avoidance

General

Function:

ID #: 281

Message: Imminent collision warning

File: warning 1.jpg

Source: SODS

Notes:

ID #: 399

Message: Imminent collision warning

File: warning 2.jpg

Source: SODS

Notes:

ID #: 332

Message: Imminent collision warning

File: warning 3.jpg

Source: SODS

Notes:

ID #: 53

Message: Imminent collision warning

File: warning 4.jpg

Source: SODS

Notes:

ID #: 172

Message: Imminent collision warning

File: warning 5.jpg

Source: SODS

Notes:

Collision Avoidance Information

Collision avoidance

General

Function:

ID #: 303

Message: Traffic collision

File: trafficCollision.gif

Source: Industry

Notes:

Collision Avoidance Information

Forward collision avoidance

General

Function:

ID #: 85

Message: Forward vehicle crash 

warning

File: Crash warning front.jpg

Source: Teague

Notes:

ID #: 326

Message: Forward vehicle crash 

warning

File: ForwardCollisionAvoidance7C-1.jpg

Source: ISO (proposed)

Notes:

ID #: 162

Message: Forward vehicle crash 

warning

File: ForwardCollisionAvoidance7C-2.jpg

Source: ISO (proposed)

Notes:

8-6
Icon Details by Icon Type

Collision Avoidance Information

Forward collision avoidance

General

Function:

ID #: 293

Message: Forward vehicle crash 

warning

File: ForwardCollisionAvoidance7C-3.jpg

Source: ISO (proposed)

Notes:

ID #: 260

Message: Forward vehicle crash 

warning system failure

File: ForwardCollisionAvoidance7C-4.jpg

Source: ISO (proposed)

Notes:

ID #: 373

Message: Forward vehicle crash 

warning system failure

File: ForwardCollisionAvoidance7C-5.jpg

Source: ISO (proposed)

Notes:

ID #: 59

Message: Forward vehicle crash 

warning system failure

File: ForwardCollisionAvoidance7C-6.jpg

Source: ISO (proposed)

Notes:

Collision Avoidance Information

Rear-end collision avoidance

General

Function:

ID #: 363

Message: Alert level

File: AlertLvl.gif

Source: Industry

Notes:

ID #: 385

Message: Imminent collision warning

File: Crash warning rear.jpg

Source: Teague

Notes:

ID #: 44

Message: Imminent collision warning

File: Head on.jpg

Source: Corel ®

Notes: edited

Collision Avoidance Information

Road departure

General

Function:

ID #: 386

Message: Lane departure warning

File: RoadDeparture7E-1.jpg

Source: ISO (proposed)

Notes:

8-7
Icon Details by Icon Type

Collision Avoidance Information

Side collision avoidance

General

Function:

ID #: 296

Message: Imminent collision warning

File: Collision Left.jpg

Source: SODS

Notes:

ID #: 106

Message: Imminent collision warning

File: Collision Right.jpg

Source: SODS

Notes:

ID #: 37

Message: Imminent collision warning

File: crash 2.jpg

Source: Teague

Notes:

ID #: 116

Message: Imminent collision warning

File: Red car left.jpg

Source: SODS

Notes:

ID #: 349

Message: Imminent collision warning

File: Red car right.jpg

Source: SODS

Notes:

Collision Avoidance Information

Side collision avoidance

General

Function:

ID #: 416

Message: Imminent collision warning

File: warning 6.jpg

Source: SODS

Notes:

ID #: 256

Message: No left turn

File: No left turn.jpg

Source: SODS

Notes:

ID #: 275

Message: No right turn

File: No right turn.jpg

Source: SODS

Notes:

ID #: 55

Message: Side obstacle warning

File: LaneChange7F-1.jpg

Source: ISO (proposed)

Notes:

ID #: 317

Message: Side obstacle warning

File: LaneChange7F-2.jpg

Source: ISO (proposed)

Notes:

8-8
Icon Details by Icon Type

Collision Avoidance Information

Side collision avoidance

General

Function:

ID #: 306

Message: Side obstacle warning

File: LaneChange7F-3.jpg

Source: ISO (proposed)

Notes:

ID #: 407

Message: Side obstacle warning

File: LaneChange7F-4.jpg

Source: ISO (proposed)

Notes:

Collision Avoidance Information

System status

General

Function:

ID #: 235

Message: Cautionary warning

File: Yellow Horizontal.jpg

Source: SODS

Notes:

ID #: 74

Message: Cautionary warning

File: Yellow Stripes.jpg

Source: SODS

Notes:

ID #: 299

Message: Cautionary warning

File: Yellow Triangle.jpg

Source: SODS

Notes:

Collision Avoidance Information

System status

General

Function:

ID #: 372

Message: Cautionary warning

File: Yellow Vert.jpg

Source: SODS

Notes:

ID #: 4

Message: Lane departure warning 

system failure

File: RoadDeparture7E-2.jpg

Source: ISO (proposed)

Notes:

ID #: 421

Message: Lane departure warning 

system off or not available

File: RoadDeparture7E-3.jpg

Source: ISO (proposed)

Notes:

ID #: 378

Message: Side obstacle warning 

system failure

File: LaneChange7F-5.jpg

Source: ISO (proposed)

Notes:

ID #: 24

Message: Side obstacle warning 

system failure

File: LaneChange7F-6.jpg

Source: ISO (proposed)

Notes:

8-9
Icon Details by Icon Type

Collision Avoidance Information

System status

General

Function:

ID #: 397

Message: Side obstacle warning 

system failure

File: LaneChange7F-7.jpg

Source: ISO (proposed)

Notes:

ID #: 274

Message: Side obstacle warning 

system failure

File: LaneChange7F-8.jpg

Source: ISO (proposed)

Notes:

ID #: 45

Message: System failure

File: ex.jpg

Source: SODS

Notes:

ID #: 63

Message: System failure

File: System Malfunction.jpg

Source: SODS

Notes:

ID #: 78

Message: System failure

File: x in triangle.jpg

Source: http://members.arttoday.com/

Notes: warning03bw.jpg

Collision Avoidance Information

System status

General

Function:

ID #: 300

Message: System on and functioning

File: circle.jpg

Source: SODS

Notes:

ID #: 36

Message: System on and functioning

File: System Check.jpg

Source: SODS

Notes:

ID #: 123

Message: System on and functioning

File: System OK.jpg

Source: SODS

Notes:

Commercial Vehicle Operations 

Information

Augmented signage information

General

Function:

ID #: 1

Message: Allowable vehicle length on 

roadway

File: truck width.gif

Source: Corel ®

Notes:

8-10
Icon Details by Icon Type

Commercial Vehicle Operations 

Information

Augmented signage information

General

Function:

ID #: 6

Message: Allowable vehicle width on 

roadway

File: width.jpg

Source: Corel ®

Notes:

ID #: 350

Message: Hazardous cargo not 

allowed

File: no HC.jpg

Source: Corel ®

Notes:

ID #: 125

Message: Low clearance

File: 13-6.jpg

Source: http://members.aol.com/rcmo

eur/r12.html

Notes:

ID #: 11

Message: Low clearance

File: 3.5.jpg

Source: Corel ®

Notes:

ID #: 379

Message: Weight limits

File: 5.4.gif

Source: http://members.aol.com/rcmo

eur/d8.html

Notes: edited

Commercial Vehicle Operations 

Information

Augmented signage information

General

Function:

ID #: 396

Message: Weight limits

File: weight.jpg

Source: http://members.aol.com/rcmo

eur/d8.html

Notes:

Commercial Vehicle Operations 

Information

Cargo and vehicle monitoring 

information

General

Function:

ID #: 328

Message: Problem in the trailer unit

File: truck.gif

Source: http://www.nzwwa.com/mirror/

clipart/graphics/pictures/signs

/index.html + 

http://members.aol.com/rcmo

eur/r12.html

Notes: edited

Commercial Vehicle Operations 

Information

Trip planning

General

Function:

ID #: 175

Message: Diesel fuel location

File: diesel.jpg

Source: Corel ®

Notes:

8-11
Icon Details by Icon Type

Commercial Vehicle Operations 

Information

Trip planning

General

Function:

ID #: 141

Message: Truck stop

File: truck stop 1.gif

Source: http://members.aol.com/rcmo

eur/rg.html + 

http://members.aol.com/rcmo

eur/rm.html + 

http://members.aol.com/rcmo

eur/d9.html

Notes: icons merged, edited

General Navigation System Information

GPS status information

General

Function:

ID #: 84

Message: Magnify/minimize map view

File: magnify.jpg

Source: Adobe exchange 3.0

Notes:

ID #: 184

Message: Satellite signal strength

File: satellite 1.jpg

Source: Corel ®

Notes:

ID #: 330

Message: Satellite signal strength

File: satellite 2.jpg

Source: Corel ®

Notes:

General Navigation System Information

GPS status information

General

Function:

ID #: 60

Message: Satellite signal strength

File: satellite 3.jpg

Source: Corel ®

Notes:

Motorist Services Information

Broadcast service/attractions

Airport

Function:

ID #: 335

Message: Airport

File: Airport.gif

Source: MUTCD

Notes: edited

ID #: 427

Message: Airport

File: poiAirports.gif

Source: Industry

Notes:

ID #: 156

Message: Airport information

File: Airport Info.jpg

Source: http://members.arttoday.com/

Notes: airportinfo01bw.jpg

8-12
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business general

Function:

ID #: 81

Message: ATM

File: poiAtm.gif

Source: Industry

Notes:

ID #: 242

Message: Bank

File: $building.jpg

Source: http://members.arttoday.com/

Notes: bank01bw.jpg

ID #: 66

Message: Coffee shop

File: coffee.jpg

Source: http://www.geneseo.edu/icons

/symbols/index.html

Notes:

ID #: 160

Message: Coffee shop

File: coffeeShops.gif

Source: Industry

Notes:

ID #: 109

Message: Directory (index of yellow 

pages)

File: 2 fingers.jpg

Source: http://yp.yahoo.com

Notes:

Motorist Services Information

Broadcast service/attractions

Business general

Function:

ID #: 51

Message: Electric company

File: poiElectricCompany.gif

Source: Industry

Notes:

ID #: 380

Message: Electronics

File: poiElectronic.gif

Source: Industry

Notes:

ID #: 424

Message: Florist

File: poiFlorists.gif

Source: Industry

Notes:

ID #: 88

Message: Gas utility

File: poiGasUtility.gif

Source: Industry

Notes:

ID #: 343

Message: Ice cream shop

File: icecream.jpg

Source: www.iconbazaar.com

Notes:

8-13
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business general

Function:

ID #: 212

Message: Kennel

File: Kennel.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 388

Message: Laundry

File: Washer & dryer.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 276

Message: Locker

File: Key.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 334

Message: Lodging

File: poiLodging.gif

Source: Industry

Notes:

ID #: 377

Message: Real estate

File: poiRealEstate.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business general

Function:

ID #: 390

Message: Window glass

File: poiWindowGlass.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/auto

Function:

ID #: 368

Message: Auto glass

File: poiAutoGlass.gif

Source: Industry

Notes:

ID #: 250

Message: Auto parts

File: poiAutoParts.gif

Source: Industry

Notes:

ID #: 161

Message: Auto service

File: poiAutoService.gif

Source: Industry

Notes:

ID #: 135

Message: Auto tires

File: poiAutoTires.gif

Source: Industry

Notes:

8-14
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business/auto

Function:

ID #: 25

Message: Auto transmission

File: poiAutoTransmission.gif

Source: Industry

Notes:

ID #: 404

Message: Car mechanic

File: wrench.jpg

Source: Teague

Notes:

ID #: 180

Message: Car rental agency

File: keycar.jpg

Source: http://membersarttoday.com/

Notes:

ID #: 82

Message: Car wash

File: poiCarWash.gif

Source: Industry

Notes:

ID #: 307

Message: Fuel

File: poiFuel.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/auto

Function:

ID #: 148

Message: Gas station ahead

File: gas3.jpg

Source: Teague

Notes:

ID #: 347

Message: Rental car

File: poiRentalCar.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/retail

Function:

ID #: 110

Message: Department store

File: poiDepartmentStores.gif

Source: Industry

Notes:

ID #: 70

Message: Furniture store

File: poiFurniture.gif

Source: Industry

Notes:

ID #: 361

Message: Grocery store

File: grocery.jpg

Source: http://members.arttoday.com/

Notes:

8-15
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business/retail

Function:

ID #: 72

Message: Grocery store

File: grocery2.jpg

Source: http://members.arttoday.com/

Notes:

ID #: 252

Message: Grocery store

File: poiGroceries.gif

Source: Industry

Notes:

ID #: 294

Message: Hardware store

File: poiHardware.gif

Source: Industry

Notes:

ID #: 288

Message: Home center

File: poiHomeCenter.gif

Source: Industry

Notes:

ID #: 187

Message: Office supply

File: poiOfficeSupply.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/retail

Function:

ID #: 193

Message: Photo equipment

File: poiPhotoEquip.gif

Source: Industry

Notes:

ID #: 339

Message: Software

File: poiSoftware.gif

Source: Industry

Notes:

ID #: 223

Message: Toy store

File: poiToyStore.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/service

Function:

ID #: 132

Message: Attorney

File: poiAttorneys.gif

Source: Industry

Notes:

ID #: 220

Message: Barber shop

File: barber.gif

Source: http://www.hardhatusa.com/c

at162.html

Notes: ill0022, edited

8-16
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business/service

Function:

ID #: 412

Message: Dry cleaning

File: poiDryCleaning.gif

Source: Industry

Notes:

ID #: 255

Message: Food

File: poiFood.gif

Source: Industry

Notes:

ID #: 165

Message: Hair salon

File: poiHairSalons.gif

Source: Industry

Notes:

ID #: 417

Message: House cleaning

File: poiHouseCleaning.gif

Source: Industry

Notes:

ID #: 302

Message: Lawn service

File: poiLawnService.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Business/service

Function:

ID #: 71

Message: Pest service

File: poiPestService.gif

Source: Industry

Notes:

ID #: 370

Message: Photo copy

File: poiPhotoCopy.gif

Source: Industry

Notes:

ID #: 94

Message: Photo developing

File: poiPhotoDeveloping.gif

Source: Industry

Notes:

ID #: 333

Message: Plumbing/heating

File: poiPlumbHeat.gif

Source: Industry

Notes:

ID #: 217

Message: Pool service

File: poiPoolService.gif

Source: Industry

Notes:

8-17
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Business/service

Function:

ID #: 236

Message: Roof service

File: poiRoofService.gif

Source: Industry

Notes:

ID #: 107

Message: Security

File: poiSecurity.gif

Source: Industry

Notes:

ID #: 150

Message: Tailor

File: poiTailors.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Entertainment

Function:

ID #: 367

Message: Amphitheater

File: Theatre.gif

Source: MUTCD

Notes: edited

ID #: 80

Message: Arts and culture venue

File: mask1.gif

Source: http://www.hardhatusa.com/c

at161.html

Notes: gsl0035, edited

Motorist Services Information

Broadcast service/attractions

Entertainment

Function:

ID #: 111

Message: Casino

File: poiCasinos.gif

Source: Industry

Notes:

ID #: 154

Message: Casino

File: Roulette.jpg

Source: Corel ®

Notes:

ID #: 429

Message: Casino

File: Slot Machine.jpg

Source: http://members.arttoday.com/

Notes: casino01bw.jpg

ID #: 284

Message: Live music

File: poiLiveMusic.gif

Source: Industry

Notes:

ID #: 43

Message: Movie theater

File: action.jpg

Source: http://www.geneseo.edu/icons

/symbols/index.html

Notes:

8-18
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Entertainment

Function:

ID #: 214

Message: Movie theater

File: poiCinema.gif

Source: Industry

Notes:

ID #: 101

Message: Movie theater

File: Projecter 1.jpg

Source: http://www.geneseo.edu/icons

/symbols/index.html

Notes:

ID #: 346

Message: Movie theater

File: Projecter 2.jpg

Source: Corel ®

Notes:

ID #: 27

Message: Music venue

File: Music note.jpg

Source: http://www.geneseo.edu/icons

/symbols/index.html

Notes:

ID #: 167

Message: Night life attraction

File: martini.gif

Source: http://hardhatusa.com/cat162.

html

Notes: ill0015, edited

Motorist Services Information

Broadcast service/attractions

Entertainment

Function:

ID #: 179

Message: Theater

File: Masks2.jpg

Source: Corel ®

Notes:

ID #: 137

Message: Theater

File: Masks3.jpg

Source: http://www.artsci.wust1.edu/~

dmreed/maskst.gif

Notes:

ID #: 426

Message: Theater

File: masks4.gif

Source: http://www.hardhatusa.com/c

at161.html

Notes: gsl0036, edited

ID #: 415

Message: Theater

File: masks5.gif

Source: http://www.hardhatusa.com/c

at161.html

Notes: gsl0033 [icon is both gsl0033 and gsl0034 

combined], edited

8-19
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

General

Function:

ID #: 189

Message: Church

File: poiChurches.gif

Source: Industry

Notes:

ID #: 301

Message: College

File: Grad Cap.jpg

Source: http://www.geneseo.edu/icons

/symbols/two.html

Notes:

ID #: 130

Message: Elevator

File: Elevator.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 86

Message: General winter recreation

File: Snowflake.gif

Source: MUTCD

Notes: edited

ID #: 164

Message: Information

File: Info.jpg

Source: Corel ®

Notes:

Motorist Services Information

Broadcast service/attractions

General

Function:

ID #: 362

Message: Landmark information

File: Point out.jpg

Source: Corel ®

Notes:

ID #: 425

Message: Library

File: Read.gif

Source: MUTCD

Notes: edited

ID #: 62

Message: Mail box

File: poiMailBox.gif

Source: Industry

Notes:

ID #: 237

Message: Point of interest

File: poi.gif

Source: Industry

Notes:

ID #: 395

Message: Rest area ahead

File: RestAreaAhead.gif

Source: MUTCD

Notes: edited

8-20
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

General

Function:

ID #: 338

Message: Restrooms

File: Men.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 389

Message: Restrooms

File: Restrooms.gif

Source: MUTCD

Notes: edited

ID #: 409

Message: Restrooms

File: Women.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 170

Message: School

File: Pedestrians.jpg

Source: http://members.arttoday.com/

Notes: crosswalk01w.jpg

ID #: 234

Message: Zoo

File: Zoo 1.jpg

Source: http://www.geneseo.edu/icons

/symbols/index.html

Notes:

Motorist Services Information

Broadcast service/attractions

General

Function:

ID #: 314

Message: Zoo

File: Zoo 2.jpg

Source: http://www.highways.gow.uk/e

ducate/educate.htm

Notes:

Motorist Services Information

Broadcast service/attractions

Government

Function:

ID #: 77

Message: City hall/government 

building

File: Political Building.jpg

Source: Corel ®

Notes:

ID #: 290

Message: Courthouse

File: gavel.gif

Source: http://www.hardhatusa.com/c

at161.html

Notes: gsl0042, edited

ID #: 420

Message: Courthouse

File: Scales.jpg

Source: Corel ®

Notes:

ID #: 152

Message: Post office

File: Mail 1.jpg

Source: Corel ®

Notes:

8-21
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Government

Function:

ID #: 155

Message: Post office

File: Mail 2.jpg

Source: Corel ®

Notes:

ID #: 185

Message: Post office

File: poiPostOffices.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Internet/Phone

Function:

ID #: 418

Message: Phone

File: Phone1.jpg

Source: Clickart

Notes:

ID #: 241

Message: Phone

File: Phone2.jpg

Source: Clickart

Notes:

ID #: 26

Message: Phone

File: Phone3.jpg

Source: Clickart

Notes:

Motorist Services Information

Broadcast service/attractions

Internet/Phone

Function:

ID #: 292

Message: Phone

File: Phone4.gif

Source: MUTCD

Notes: edited

ID #: 316

Message: Phone, internet connection

File: connect.jpg

Source: http://www.geneseo.edu/icons

/symbols/two.html

Notes:

ID #: 376

Message: Phone, internet connection

File: connected.jpg

Source: http://www.geneseo.edu/icons

/symbols/two.html

Notes:

ID #: 29

Message: Telephone

File: telephone.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Medical

Function:

ID #: 413

Message: Hospital

File: hospital 1.jpg

Source: http://www.dps.state.ak.us/dm

v/DLMANUAL/signs.htm

Notes:

8-22
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Medical

Function:

ID #: 352

Message: Hospital

File: Hospital 2.jpg

Source: http://members.arttoday.com/

Notes: hospital01bw.jpg

ID #: 337

Message: Hospital

File: Hospital Right.jpg

Source: http://members.aol.com/rcmo

eur/rm.html

Notes:

ID #: 272

Message: Hospital

File: Med Assist 2.jpg

Source: Corel ®

Notes:

ID #: 310

Message: Medical assistance

File: Med Assist 1.jpg

Source: www.iconbazaar.com

Notes:

ID #: 54

Message: Medical assistance

File: poiHospital.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Medical

Function:

ID #: 430

Message: Pharmacy

File: poiPharmacies.gif

Source: Industry

Notes:

ID #: 406

Message: Physician

File: poiPhysicians.gif

Source: Industry

Notes:

ID #: 263

Message: Veternarian

File: poiVeternarian.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Parking

Function:

ID #: 12

Message: Park and ride

File: park&ride.jpg

Source: http://members.aol.com/rcmo

eur/d4.html

Notes:

ID #: 323

Message: Parking

File: poiParking.gif

Source: Industry

Notes:

8-23
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Parking

Function:

ID #: 411

Message: Parking lot

File: Parking.jpg

Source: Corel ®

Notes:

ID #: 15

Message: Type of parking facility

File: wheelchair.jpg

Source: Corel ®

Notes:

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 28

Message: All-terrain vehicle trail

File: 4 wheeler.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 240

Message: Amusement park

File: Amusement park.jpg

Source: Corel ®

Notes:

ID #: 157

Message: Amusement park

File: poiAmusement.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 200

Message: Bicycle trail

File: bike 1.jpg

Source: http://members.arttoday.com/

Notes: bicycle01bw.jpg

ID #: 41

Message: Bicycle trail

File: bike 2.jpg

Source: http://members.arttoday.com/

Notes: bicycle02bw.jpg

ID #: 90

Message: Boat launching

File: boat 5.jpg

Source: http://members.arttoday.com/

Notes: boatlanding01bw.jpg

ID #: 39

Message: Campground

File: poiCampround.gif

Source: Industry

Notes:

ID #: 131

Message: Camping

File: Camping 2.gif

Source: MUTCD

Notes: edited

8-24
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 47

Message: Canoeing

File: boat 2.gif

Source: MUTCD

Notes: edited

ID #: 342

Message: Climbing

File: Rock Climbing.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 13

Message: Cross-country skiing

File: ski 2.gif

Source: http://members.aol.com/rcmo

eur/rs.html

Notes:

ID #: 360

Message: Diving

File: diver.jpg

Source: http://members.arttoday.com/

Notes:

ID #: 7

Message: Downhill skiing

File: ski 3.gif

Source: http://members.aol.com/rcmo

eur/rs.html

Notes:

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 327

Message: Fishing

File: fish.jpg

Source: http://members.arttoday.com/

Notes:

ID #: 198

Message: Fishing lake

File: poiFishingLakes.gif

Source: Industry

Notes:

ID #: 391

Message: Golf course

File: Golf 1.jpg

Source: Corel ®

Notes:

ID #: 229

Message: Golf course

File: Golf 2.jpg

Source: Corel ®

Notes:

ID #: 277

Message: Golfing

File: poiGolfing.gif

Source: Industry

Notes:

8-25
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 102

Message: Hiking

File: Hiking.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 174

Message: Horse trail

File: rider.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 423

Message: Hunting

File: Deer 1.jpg

Source: http://members.arttoday.com/

Notes:

ID #: 190

Message: Hunting

File: rifle.jpg

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 50

Message: Ice skating

File: skate.gif

Source: MUTCD

Notes: edited

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 56

Message: Kayaking

File: boat 3.jpg

Source: http://members.arttoday.com/

Notes: kayak01bw.jpg

ID #: 305

Message: Marina

File: anchor.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

ID #: 222

Message: Motor boating

File: boat 1.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

ID #: 168

Message: Motor boating

File: boat 4.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

ID #: 344

Message: Off-road trail

File: jeep.jpg

Source: http://members.arttoday.com/

Notes: atv02bw.jpg

8-26
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 428

Message: Park

File: poiParks.gif

Source: Industry

Notes:

ID #: 408

Message: Picnic area

File: Picnic.gif

Source: MUTCD

Notes: edited

ID #: 213

Message: Playground

File: teeter totter.gif

Source: MUTCD

Notes: edited

ID #: 142

Message: Recreation center

File: poiRecCenters.gif

Source: Industry

Notes:

ID #: 89

Message: Rock collecting

File: chisel.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 233

Message: Row boating

File: boat 6.jpg

Source: Teague

Notes:

ID #: 99

Message: RV park

File: Camper.jpg

Source: http://members.arttoday.com/

Notes: camper01bw.jpg

ID #: 311

Message: RV park

File: Trailer.jpg

Source: http://members.arttoday.com/

Notes: rv04bw.jpg

ID #: 112

Message: Sail-boating

File: boat 7.jpg

Source: Teague

Notes:

ID #: 283

Message: Scuba diving

File: scuba.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

8-27
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 22

Message: Shower

File: Shower.gif

Source: http://members.aol.com/rcmo

eur/ra.html

Notes:

ID #: 147

Message: Snowmobiling

File: snomobile.jpg

Source: http://members.arttoday.com/

Notes: snowmobiling04bw.jpg

ID #: 221

Message: Sport stadium

File: Stadium.gif

Source: http://kazoobiz.com/marketpla

ce/images/stadium.gif

Notes: edited

ID #: 115

Message: Stable

File: horse.gif

Source: http://members.aol.com/rcmo

eur/rl.html

Notes:

ID #: 226

Message: Surfing

File: surf.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 67

Message: Swimming

File: swim.gif

Source: MUTCD

Notes: edited

ID #: 93

Message: Tent/trailer park

File: Camping.gif

Source: http://members.arttoday.com/

Notes: rvtent01c2.jpg, edited

ID #: 329

Message: Tourist attraction

File: poiTouristAttractions.gif

Source: Industry

Notes:

ID #: 134

Message: Water sports

File: watersports.jpg

Source: Teague

Notes:

ID #: 10

Message: Water-skiing

File: ski 1.gif

Source: http://members.aol.com/rcmo

eur/rw.html

Notes:

8-28
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Recreation

Function:

ID #: 358

Message: Zoo

File: poiZoos.gif

Source: Industry

Notes:

Motorist Services Information

Broadcast service/attractions

Transit

Function:

ID #: 340

Message: Bus station

File: Bus 3.jpg

Source: http://members.arttoday.com/

Notes: bus08bw.jpg

ID #: 46

Message: Bus station

File: bus 4.jpg

Source: http://members.arttoday.com/

Notes: schoolbus02c.jpg

ID #: 61

Message: Bus station

File: Bus Left.jpg

Source: http://members.arttoday.com/

Notes: bus05bw.jpg

ID #: 16

Message: Commuter rail station

File: Bus 2.jpg

Source: http://members.arttoday.com/

Notes: subway02bw.jpg

Motorist Services Information

Broadcast service/attractions

Transit

Function:

ID #: 83

Message: Commuter rail station

File: Train 1.gif

Source: http://members.arttoday.com/

Notes: subway01bw.jpg, edited

ID #: 100

Message: Commuter rail station

File: Train 2.jpg

Source: http://members.arttoday.com/

Notes: monorail01bw.jpg

ID #: 387

Message: Commuter rail station

File: Train 3.jpg

Source: http://members.arttoday.com/

Notes: subway03bw.jpg

ID #: 49

Message: Commuter rail station

File: Train 4.jpg

Source: http://members.arttoday.com/

Notes: trolley01bw.jpg

ID #: 231

Message: Ferry terminal

File: Carferry1.jpg

Source: http://members.arttoday.com/

Notes: ferry02bw.jpg

8-29
Icon Details by Icon Type

Motorist Services Information

Broadcast service/attractions

Transit

Function:

ID #: 163

Message: Ferry terminal

File: Carferry2.jpg

Source: http://members.arttoday.com/

Notes: ferry05bw.jpg

ID #: 151

Message: Imminent collision warning

File: Train 6.gif

Source: Corel ®

Notes:

ID #: 192

Message: Train station

File: Train 5.jpg

Source: Corel ®

Notes:

Motorist Services Information

Destination coordination

General

Function:

ID #: 219

Message: Rest area exit

File: RA.jpg

Source: Corel ®

Notes:

Motorist Services Information

Email, messaging

General

Function:

ID #: 400

Message: Address book

File: addressbook.gif

Source: Industry

Notes:

ID #: 282

Message: Address book

File: addressbookAll.gif

Source: Industry

Notes:

ID #: 203

Message: Address book - business

File: addressbookBusiness.gif

Source: Industry

Notes:

ID #: 204

Message: Address book - family

File: addressbookFamily.gif

Source: Industry

Notes:

ID #: 166

Message: Address book - friends

File: addressbookFriends.gif

Source: Industry

Notes:

8-30
Icon Details by Icon Type

Motorist Services Information

Email, messaging

General

Function:

ID #: 405

Message: Users

File: users.gif

Source: Industry

Notes:

Motorist Services Information

Entertainment

General

Function:

ID #: 319

Message: CD player

File: cdPlayer.gif

Source: Industry

Notes:

ID #: 257

Message: Entertainment - sports

File: genreSports.gif

Source: Industry

Notes:

ID #: 384

Message: Entertainment - talk

File: genreTalk.gif

Source: Industry

Notes:

ID #: 422

Message: Entertainment - TV

File: genreTV.gif

Source: Industry

Notes:

Motorist Services Information

Entertainment

General

Function:

ID #: 128

Message: Favorites

File: favorites.gif

Source: Industry

Notes:

ID #: 398

Message: Music genre

File: genre.gif

Source: Industry

Notes:

ID #: 365

Message: Music genre

File: genreOther.gif

Source: Industry

Notes:

ID #: 394

Message: Music genre - alternative

File: genreAlternative.gif

Source: Industry

Notes:

ID #: 121

Message: Music genre - classic rock

File: genreClassicRock.gif

Source: Industry

Notes:

8-31
Icon Details by Icon Type

Motorist Services Information

Entertainment

General

Function:

ID #: 127

Message: Music genre - classical

File: genreClassical.gif

Source: Industry

Notes:

ID #: 392

Message: Music genre - country

File: genreCountry.gif

Source: Industry

Notes:

ID #: 270

Message: Music genre - easy listening

File: genreEasyListening.gif

Source: Industry

Notes:

ID #: 19

Message: Music genre - latin

File: genreLatin.gif

Source: Industry

Notes:

ID #: 34

Message: Music genre - oldies

File: genreOldies.gif

Source: Industry

Notes:

Motorist Services Information

Entertainment

General

Function:

ID #: 419

Message: Music genre - R&B, rap

File: genreR&BRap.gif

Source: Industry

Notes:

ID #: 254

Message: Music genre - rock

File: genreRock.gif

Source: Industry

Notes:

ID #: 140

Message: Music genre - top 40

File: genreTop40.gif

Source: Industry

Notes:

ID #: 79

Message: News

File: genreNews.gif

Source: Industry

Notes:

ID #: 17

Message: Radio

File: radio.gif

Source: Industry

Notes:

8-32
Icon Details by Icon Type

Motorist Services Information

Entertainment

General

Function:

ID #: 253

Message: Radio - AM

File: radioAM.gif

Source: Industry

Notes:

ID #: 181

Message: Video rental

File: poiVideoRent.gif

Source: Industry

Notes:

Motorist Services Information

Internet access

General

Function:

ID #: 144

Message: Stocks

File: stocks.gif

Source: Industry

Notes:

ID #: 205

Message: Stocks - DOW

File: stocksDOW.gif

Source: Industry

Notes:

ID #: 91

Message: Stocks - NASDAQ

File: stocksNASDAQ.gif

Source: Industry

Notes:

Motorist Services Information

Internet access

General

Function:

ID #: 38

Message: Stocks - Russell 2000

File: stocksR2000.gif

Source: Industry

Notes:

ID #: 232

Message: Stocks - S&P 500

File: stocksSP500.gif

Source: Industry

Notes:

Motorist Services Information

Message transfer

General

Function:

ID #: 52

Message: Incoming message

File: files.jpg

Source: http://www.awesomeicons.co

m

Notes:

ID #: 381

Message: Message sent/send 

message

File: flying letter.jpg

Source: http://www.awesomeicons.co

m

Notes:

8-33
Icon Details by Icon Type

Motorist Services Information

Message transfer

General

Function:

ID #: 215

Message: Problem with sent e-mail

File: lightning letter.gif

Source: http://www.awesomeicons.co

m

Notes: edited

ID #: 201

Message: Reply to a message

File: reply.jpg

Source: Netscape Communicator 

4.04 ®

Notes:

ID #: 124

Message: Retrieve message

File: get msg.jpg

Source: Netscape Communicator 

4.04 ®

Notes:

ID #: 58

Message: Save message

File: file.jpg

Source: Corel ®

Notes:

ID #: 243

Message: Write message

File: pencil-paper.jpg

Source: http://www.cit.gu.edu.au/imag

es/Images.html

Notes:

Routing and Navigation

Route guidance

Emergency vehicles

Function:

ID #: 245

Message: Approaching emergency 

vehicle

File: Emergency veh1.jpg

Source: Teague

Notes:

ID #: 118

Message: Approaching emergency 

vehicle

File: Emergency veh2.jpg

Source: Teague

Notes:

ID #: 202

Message: Approaching emergency 

vehicle

File: fire.jpg

Source: Teague

Notes:

ID #: 410

Message: Approaching emergency 

vehicle

File: red cross vehicle.jpg

Source: Teague

Notes:

8-34
Icon Details by Icon Type

Routing and Navigation

Route guidance

General

Function:

ID #: 291

Message: Route home

File: RouteGuidance1D-1.jpg

Source: ISO (proposed)

Notes:

ID #: 3

Message: Vehicle's current position

File: Star.jpg

Source: Corel ®

Notes:

ID #: 133

Message: Vehicle's current position

File: You're here.gif

Source: 5www.etak.com/skymap/inde

x/html

Notes: edited

Routing and Navigation

Route guidance

Road closures

Function:

ID #: 239

Message: Construction ahead - 

alternate route

File: Exit for construction.jpg

Source: Teague

Notes:

ID #: 248

Message: Crash ahead - alternate 

route

File: lanes blocked 1.jpg

Source: Teague

Notes:

Routing and Navigation

Route guidance

Road closures

Function:

ID #: 178

Message: Hazardous spill ahead - 

alternate route

File: lanes blocked 2.jpg

Source: Teague

Notes:

ID #: 224

Message: Road closed ahead - 

alternate route

File: lanes blocked 3.jpg

Source: Teague

Notes:

Routing and Navigation

Route navigation

General

Function:

ID #: 403

Message: Advisory exit speed sign

File: Exit Speed.jpg

Source: http://members.aol.com/rcmo

eur/w13.html

Notes:

ID #: 120

Message: Exit

File: Exit.jpg

Source: http://members.aol.com/rcmo

eur/e.html

Notes:

8-35
Icon Details by Icon Type

Routing and Navigation

Route navigation

General

Function:

ID #: 188

Message: Lane suggestion for next 

turn

File: Right lane entering.jpg

Source: Corel ®

Notes:

ID #: 32

Message: Recent destinations

File: recentDestinations.gif

Source: Industry

Notes:

ID #: 145

Message: Turn sign

File: Sharp right turn.gif

Source: Corel ®

Notes:

Routing and Navigation

Travel coordination and planning

General

Function:

ID #: 267

Message: Start time required to catch 

other mode of transport

File: clock1.jpg

Source: http://members.arttoday.com/

Notes: time01bw.jpg

ID #: 92

Message: Start time required to catch 

other mode of transport

File: clock2.jpg

Source: http://members.arttoday.com/

Notes: time02bw.jpg

Routing and Navigation

Travel coordination and planning

General

Function:

ID #: 113

Message: Start time required to catch 

other mode of transport

File: racecars.jpg

Source: http://members.arttoday.com/

Notes: start01c.jpg

ID #: 247

Message: Total time to complete 

travel

File: All segments.jpg

Source: Drawn

Notes:

ID #: 278

Message: Travel time for one segment

File: 1segment.jpg

Source: Drawn

Notes:

Routing and Navigation

Trip planning

Attractions

Function:

ID #: 375

Message: Landmarks or 

topographical features

File: pyramids.jpg

Source: http://members.arttoday.com/

Notes: landmark03c.jpg

8-36
Icon Details by Icon Type

Routing and Navigation

Trip planning

Attractions

Function:

ID #: 153

Message: Landmarks or 

topographical features

File: Statue Lib.jpg

Source: http://members.arttoday.com/

Notes: landmark04c.jpg

ID #: 279

Message: Landmarks or 

topographical features

File: WhiteHouse.jpg

Source: http://members.arttoday.com/

Notes: landmark05c.jpg

ID #: 182

Message: Locations of state and 

national parks

File: Natl park.gif

Source: MUTCD

Notes: edited

Routing and Navigation

Trip planning

Costs

Function:

ID #: 9

Message: Number of tolls and cost of 

each toll per segment

File: Toll.jpg

Source: http://www.ettm.com, 

http://members.arttoday.com/,

Notes:

Routing and Navigation

Trip planning

Costs

Function:

ID #: 194

Message: Price range of food at 

restaurants

File: Food Price.jpg

Source: Teague

Notes:

ID #: 359

Message: Total trip cost

File: money1.jpg

Source: http://members.arttoday.com/

Notes: dollar02bw.jpg

ID #: 269

Message: Total trip cost

File: money2.jpg

Source: http://members.arttoday.com/

Notes: dollar03bw.jpg

ID #: 364

Message: Total trip cost

File: money3.jpg

Source: http://members.arttoday.com/

Notes: dollar04bw.jpg

Routing and Navigation

Trip planning

General

Function:

ID #: 308

Message: Crime warning

File: Gun.jpg

Source: Corel ®

Notes: edited

8-37
Icon Details by Icon Type

Routing and Navigation

Trip planning

General

Function:

ID #: 369

Message: Fastest route available

File: quicktrip.jpg

Source: Rand McNally 1996 edition

Notes:

ID #: 230

Message: Length of wait

File: Sit time.jpg

Source: http://members.arttoday.com/

Notes: time03bw.jpg

ID #: 273

Message: Most scenic route

File: scenery.jpg

Source: Rand McNally 1996 edition

Notes:

ID #: 48

Message: Number of traffic 

lights/stops of route options

File: Stoplight.jpg

Source: Corel ®

Notes: suggest combining icon with digital display 

below

ID #: 298

Message: Road end/ bridge out

File: roadend.jpg

Source: Corel ®

Notes:

Routing and Navigation

Trip planning

General

Function:

ID #: 225

Message: Route avoiding tollways

File: No Toll.jpg

Source: http://www.thruway.state.ny.u

s/+editing and 

http:/www.dhp.nl/traffic/infoe.html

Notes:

ID #: 297

Message: States, regions, 

communities, and districts 

along the route

File: map.jpg

Source: http://members.arttoday.com/

Notes: unitedstates03bw.jpg

ID #: 325

Message: Transit schedules in areas 

along route

File: Bus 1.jpg

Source: http://members.arttoday.com/

Notes: transit03bw.jpg

ID #: 21

Message: Type of roads on route

File: gravel.jpg

Source: http://members.aol.com/rcmo

eur/w8.html

Notes: Indicates transition from concrete to gravel, 

edited

8-38
Icon Details by Icon Type

Routing and Navigation

Trip planning

General

Function:

ID #: 353

Message: Type of roads on route

File: tunnel.jpg

Source: http://members.arttoday.com/

Notes: tunnel01bw.jpg

Routing and Navigation

Trip planning

Lodging

Function:

ID #: 382

Message: Lodging

File: Lodging.jpg

Source: Teague

Notes:

ID #: 76

Message: No vacancy

File: No vacancy X.jpg

Source: http://members.arttoday.com/ 

+ editing

Notes: lodging 04bw.jpg

ID #: 136

Message: No vacancy

File: No vacancy.jpg

Source: Corel ®

Notes: No Vacancy

ID #: 356

Message: Price of lodging

File: No vacancy$.gif

Source: http://members.aol.com/rcmo

eur/rm.html + editing

Notes: Superimposed text when motels are full, 

edited

Routing and Navigation

Trip planning

Lodging

Function:

ID #: 35

Message: Price of lodging

File: Price lodging.jpg

Source: Teague

Notes:

ID #: 320

Message: Restaurant/food ahead

File: Food plate.jpg

Source: Corel ®

Notes:

ID #: 218

Message: Restaurant/food ahead

File: Food.gif

Source: http://members.aol.com/rcmo

eur/rm.html

Notes: edited

ID #: 177

Message: Restaurant/food ahead

File: utensils.jpg

Source: Teague

Notes:

ID #: 196

Message: Vacancy

File: vacancy.jpg

Source: Corel ®

Notes: Vacancy

8-39
Icon Details by Icon Type

Safety and Warning Information

Airbag status/information

General

Function:

ID #: 286

Message: Airbag

File: AirBagStatus-Information4G-4.jpg

Source: ISO

Notes:

ID #: 30

Message: Driver airbag off or not 

available

File: AirBagStatus-Information4G-5.jpg

Source: ISO

Notes:

ID #: 259

Message: Passenger airbag

File: AirBagStatus-Information4G-1.jpg

Source: ISO

Notes:

ID #: 280

Message: Passenger airbag off or not 

available

File: AirBagStatus-Information4G-2.jpg

Source: ISO

Notes:

ID #: 64

Message: Side impact airbag

File: AirBagStatus-Information4G-3.jpg

Source: ISO

Notes:

Safety and Warning Information

Automatic/manual aid request

General

Function:

ID #: 348

Message: Inform driver that aid had 

been requested

File: InformDriverAidRequested.jpg

Source: Corel ®

Notes:

Safety and Warning Information

Immediate hazard warning

General

Function:

ID #: 149

Message: Emergency vehicle 

stopped ahead

File: right lane x.jpg

Source: Teague

Notes:

Safety and Warning Information

Parking aids

General

Function:

ID #: 33

Message: Parking aid

File: ParkingAids4F-5.jpg

Source: ISO

Notes:

ID #: 103

Message: Parking aid off or not 

available

File: ParkingAids4F-1.jpg

Source: ISO (proposed)

Notes:

8-40
Icon Details by Icon Type

Safety and Warning Information

Parking aids

General

Function:

ID #: 266

Message: Parking aid off or not 

available

File: ParkingAids4F-2.jpg

Source: ISO (proposed)

Notes:

ID #: 171

Message: Parking aid system failure

File: ParkingAids4F-3.jpg

Source: ISO (proposed)

Notes:

ID #: 249

Message: Parking aid system failure

File: ParkingAids4F-4.jpg

Source: ISO (proposed)

Notes:

ID #: 138

Message: Reverse/ backing aid

File: ParkingAids4F-6.jpg

Source: ISO (proposed)

Notes:

ID #: 315

Message: Reverse/ backing aid failure

File: ParkingAids4F-7.jpg

Source: ISO (proposed)

Notes:

Safety and Warning Information

Parking aids

General

Function:

ID #: 159

Message: Reverse/ backing aid failure

File: ParkingAids4F-8.jpg

Source: ISO (proposed)

Notes:

Safety and Warning Information

Road condition information

General

Function:

ID #: 261

Message: Accident ahead

File: right lane x 3.jpg

Source: Teague

Notes:

ID #: 357

Message: Fallen rock ahead

File: rocks.gif

Source: http://members.arttoday.com/

Notes: fallingrock01bw.jpg, edited

ID #: 5

Message: Icy roads ahead

File: slippery.jpg

Source: http://members.arttoday.com/

Notes: slippery02bw.jpg

ID #: 197

Message: Lanes blocked ahead

File: right lane x 4.jpg

Source: Teague

Notes:

8-41
Icon Details by Icon Type

Safety and Warning Information

Road condition information

General

Function:

ID #: 122

Message: Low shoulder

File: slow 3.jpg

Source: Teague

Notes:

ID #: 191

Message: Road closed

File: trafficConstruction.gif

Source: Industry

Notes:

ID #: 312

Message: Road closed ahead

File: Road Closed.jpg

Source: http://members.arttoday.com/

Notes: roadclosed01bw.jpg

ID #: 227

Message: Road work/construction 

ahead

File: right lane x 2.jpg

Source: Teague

Notes:

ID #: 322

Message: Road work/construction 

ahead

File: slow 1.jpg

Source: Teague

Notes:

Safety and Warning Information

Road condition information

General

Function:

ID #: 98

Message: Traffic congestion

File: traffic.jpg

Source: Campbell, J. L., Carney, C., 

& Kantowitz, B. H. (1998). 

Human factors design 

guidelines for advanced 

traveler information systems 

(ATIS) and commercial 

vehicle operations (CVO) 

(FHWA-RD-98-057). 

Washington, DC: Federal 

Highway Administration.

Notes:

ID #: 40

Message: Traffic congestion

File: trafficCongestion.gif

Source: Industry

Notes:

ID #: 285

Message: Traffic event

File: trafficEvent.gif

Source: Industry

Notes:

ID #: 186

Message: Traffic/congestion ahead

File: 3 cars.jpg

Source: Corel ®

Notes:

8-42
Icon Details by Icon Type

Safety and Warning Information

Road condition information

General

Function:

ID #: 295

Message: Uneven road ahead

File: slow 2.jpg

Source: Teague

Notes:

Safety and Warning Information

Vehicle condition monitoring

Information

Function:

ID #: 75

Message: Provide more detailed 

information at the drivers 

request

File: help 2.jpg

Source: Corel ®

Notes:

ID #: 331

Message: Provide more detailed 

information at the drivers 

request

File: help 3.jpg

Source: Corel ®

Notes:

Safety and Warning Information

Vehicle condition monitoring

Mechanical

Function:

ID #: 374

Message: Inform driver of current 

problem

File: wrench 1.jpg

Source: Teague

Notes:

Safety and Warning Information

Vehicle condition monitoring

Mechanical

Function:

ID #: 108

Message: Low oil pressure

File: lamp.jpg

Source: Corel ®

Notes:

Safety and Warning Information

Vehicle condition monitoring

Tires

Function:

ID #: 313

Message: Chains required/ 

recommended

File: tire 3.jpg

Source: http://members.arttoday.com/

Notes: tire01bw.jpg

ID #: 321

Message: Low tire pressure

File: tire 2.jpg

Source: Teague

Notes:

ID #: 258

Message: Low tire pressure

File: tire.jpg

Source: Campbell, J. L., Carney, C., 

& Kantowitz, B. H. (1998). 

Human factors design 

guidelines for advanced 

traveler information systems 

(ATIS) and commercial 

vehicle operations (CVO) 

(FHWA-RD-98-057). 

Washington, DC: Federal 

Highway Administration.

Notes:

8-43
Icon Details by Icon Type

Safety and Warning Information

Vehicle condition monitoring

Tires

Function:

ID #: 23

Message: Tire failure

File: VehicleCondition4E-1.jpg

Source: ISO

Notes:

ID #: 304

Message: Tire pressure

File: VehicleCondition4E-2.jpg

Source: ISO

Notes:

ID #: 265

Message: Tire pressure

File: VehicleCondition4E-3.jpg

Source: ISO

Notes:

ID #: 158

Message: Tire pressure warning

File: icon4_car2.gif

Source: NHTSA (tested)

Notes: edited

ID #: 355

Message: Tire pressure warning

File: Wheel2_Flat1 inverted.jpg

Source: NHTSA (tested)

Notes:

Safety and Warning Information

Vehicle condition monitoring

Tires

Function:

ID #: 402

Message: Tire temperature

File: VehicleCondition4E-4.jpg

Source: ISO

Notes:

Safety and Warning Information

Weather information

General

Function:

ID #: 97

Message: Cloudy

File: weatherCloudy.gif

Source: Industry

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8-48
CHAPTER 9: TUTORIALS 

TUTORIAL 1: ANALYSIS OF RANK ORDER DATA 

In this tutorial, we describe the types of information that can be obtained from rank-order data. 

We assume that the data is collected in the following manner. A total of nj judges are asked to 

rank order ns stimuli (e.g., icons) with respect to some attribute (e.g., appropriateness for a 

specific message). Usually the whole set of stimuli is presented together, and the judges are 

allowed to proceed as they wish as long as each judge comes through with a single rank order 

along the attribute specified. If many stimuli are presented, it might be useful for the judges to 

sort them roughly into grades before attempting the final ranking. A hypothetical data set is 

presented in table 9-1. These hypothetical data might be obtained from 10 individuals who rank 

ordered 5 icons (icons A, B, C, D, and E) in appropriateness for a specific message. The icons 

would be assigned ranks of 1-5, with “1” corresponding to the icon considered to be the most 

appropriate.1

Table 9-1. Sample Data Set: Ranks Assigned to 5 Icons by 10 Judges

Ranks Assigned 

Judge 

Icon A Icon B Icon C Icon D Icon E 

1 4 2 1 3 5

2 4 2 1 3 5

3 2 1 3 4 5

4 3 1 2 4 5

5 3 4 1 2 5

6 3 2 1 4 5

7 4 3 1 2 5

8 4 2 3 1 5

9 4 2 1 3 5

10 4 1 2 3 5

Our goal is to investigate whether and how much the judged stimuli differ with respect to the 

attribute of interest. This goal can be accomplished at different levels using different methods of 

 1 When obtaining initial rank scores, lower rank scores are assigned to the icons judged to be more appropriate 

in accordance with traditional and accepted ranking methods. Elsewhere in this tutorial (e.g., see page 9-5), we see 

that the icons judged to be more appropriate are designated with higher values, not lower values. This reversal 

occurs when computing p, z, and R values, and is an expected mathematical outcome of transforming rank score 

values to interval-scale values. 

 9-1
analysis. In the following sections, we discuss some of these methods. First, we indicate a quick 

way to determine a composite rank order for the stimuli. Second, we discuss the use of mean 

ranks. Third, we outline two methods of obtaining scores for the stimuli on an interval scale. In 

addition to a general rank ordering, these scores provide an indication of relative differences 

among the stimuli. Finally, we discuss the use of more advanced and complex statistical 

methods that allow us to test whether the stimuli are truly different with respect to the attribute of 

interest. 

1. DERIVING RANK ORDER FROM SUMS OF ASSIGNED RANKS 

A composite ranking for the stimuli can be obtained by computing the sums of the rank values 

assigned to each of the stimulus. The order of the magnitudes of the sums will indicate an 

ordering of the stimuli, with the lowest sum corresponding to the stimulus judged as the best. 

For example, for the raw data of table 9-1, we obtain the sums presented in table 9-2, which 

indicate the following composite rank order from the most to least appropriate icon: C, B, D, A, 

and E. 

Table 9-2. A Composite Ranking of Icons Obtained from Sums of Assigned Ranks

Icon A Icon B Icon C Icon D Icon E 

Sum of assigned ranks (S) 35 20 16 29 50

Composite rank 4 2 1 3 5

2. OBTAINING MEAN RANKS 

Mean ranks are obtained for each icon by dividing the sum of the ranks assigned to that icon by 

the number of judges. For example, for the raw data of table 9-1, the mean rank of icon A is 

35/10 = 3.5. Mean ranks corresponding to all five icons in the sample data set are presented in 

table 9-3. In general, mean ranks will somewhat agree with the composite ranks in both order 

and spacing. 

Table 9-3. Mean Rank of Each of the Icons

Icon A Icon B Icon C Icon D Icon E 

Sum of assigned ranks (S) 35 20 16 29 50

Mean Rank (Mr) = S/nj 3.5 2 1.6 2.9 5

It should be noted that mean ranks should never be used to judge the absolute differences 

between the stimuli. For example, on the basis of the data presented in table 9-3, we could not 

conclude that icon E was judged to be 1.5 times more inappropriate than icon A. At best, mean 

ranks provide an indication of relative differences. For example, mean ranks in table 9-3 

indicate that the difference between icons B and A is the same as the difference between icon A 

 9-2
and E. However, the reader should be warned that rank values are strictly ordinal numbers2

 and 

there is little numerical meaning to be attached to means of such values. To obtain more precise 

relative differences between the stimuli, we recommend the use of the scaling methods discussed 

in the next section. 

3. OBTAINING INTERVAL-SCALE VALUES 

As mentioned above, rank data (i.e., the rank orders produced by the judges) are on an ordinal 

scale. This scale arranges things in order of magnitude, but does not reveal the magnitude of the 

differences between them. An interval scale, on the other hand, allows statements about how 

much difference there is between two objects. A good example for an interval scale is the 

Fahrenheit scale of temperature. Here, it is meaningful to say that there is as much difference 

between 60 oF and 70 oF as there is between 70 oF and 80 oF. Note, however, that interval-scale 

values are not absolute magnitudes. For instance, it is not accurate to say that 80 oF is twice as 

high as 40 oF. 

Using rank orders generated by a group of judges, it is possible to obtain interval-scale values for 

the ranked items. Below, we discuss two different methods of obtaining interval-scale values 

using rank order data: (1) Choice Score Method, and (2) Torgerson’s Categorical Scaling 

Method. The reader should keep in mind that the values obtained using either of the scaling 

methods are not meaningful in absolute terms, but that they give only an indication of relative 

differences between the stimuli. As an example, let us assume that we have obtained scale 

values of 2.5, 5, and 7.5 for icons A, B, and C, respectively. Based on these values, we cannot 

conclude that icon A is three times as good (or appropriate) as icon C. However, we can say that 

there is as much difference between icons A and B as there is between B and C. Such 

information can be important to icon designers, who frequently must make tradeoffs among 

design issues such as cost, driver performance, and driver preferences. Converting the rankorder data to an interval scale allows for more systematic and rigorous tradeoff analyses to be 

conducted. 

A. Choice Score Method 

This scaling procedure, described in Engen (1971), converts rank orders to choice frequencies, 

then to p values, and finally to z scores (unit normal deviates). The z scores obtained represent 

scale values for the stimuli on a psychological scale with equal intervals on the assumption that

the rankings are normally distributed. The procedure is outlined below; the computations for the 

sample data set are shown in table 9-4. 

 2

 Ordinal numbers arrange things in order of magnitude. They make possible comparisons of objects of the 

type “greater than” or “less than,” but do not reveal the magnitude of the differences between them. 

 9-3
Table 9-4. Computations for the Choice Score Method

Step Icon A Icon B Icon C Icon D Icon E Mean* 

1 Mean Rank (Mr) 3.50 2.00 1.60 2.90 5.00 3.00

2 Mc = ns – Mr 1.50 3.00 3.40 2.10 0.00 2.00

3 p = Mc/(ns – 1) 0.38 0.75 0.85 0.53 0.00 0.50

4 z -0.31 0.67 1.04 0.08 – –

5 R = 5z + 6 4.45 9.35 11.20 6.40 – –

* The following can be used to check the calculations: (1) mean Mr must be equal to (ns+1)/2; (2) mean choice (Mc) 

must be equal to (ns-1)/2; (3) mean p must be equal to 0.5. 

Step 1. Calculate the mean rank (Mr) assigned to each stimulus (see table 9-2). 

Step 2. Calculate a mean choice score (Mc) for each stimulus by subtracting the mean rank from

the number of stimuli (ns). For example, the mean choice Mc score for icon A of the sample data 

set is 5 – 3.5 = 1.5. 

Step 3. Convert the mean choice scores (Mc) into p values by dividing them by (ns – 1). For 

example, the p value for icon A of the sample data set is 1.5/4 = 0.38. 

The computations performed so far can be checked with the following: 

(1) Mean Mr must equal (ns + 1)/2, 

(2) Mean Mc must equal (ns – 1)/2, and 

(3) Mean p must equal 0.5. 

For example, in table 9-4,

(1) Mean Mr = (3.50 + 2.00 + 1.60 + 2.90 + 5.00) / 5 = 3.00, 

(2) Mean Mc = (1.50 + 3.00 + 3.40 + 2.10 + 0.00) / 5 = 2.00, and 

(3) Mean p = (0.38 + 0.75 + 0.85 + 0.53 +0.00) /5 = 0.50. 

Step 4. Convert the p values into z scores using table 9-5. 

The z scores obtained in step 4 represent scores for the stimuli on an interval scale. Because the 

z values are generally awkward numbers to use, we recommend a linear transformation of the z

values to a more convenient range as explained in step 5 below. (This transformation is similar 

to converting oF temperature to oC temperature.) 

Step 5. (Optional) Obtain a linear transformation of the z scores (i.e., multiply the z scores by a 

constant and add a constant). In table 9-4, we arbitrarily use the transformation R = 5z + 6; any 

other linear transformation (e.g., R = 2z + 1) can be used. The purpose of this transformation is 

to obtain scores in a more convenient range than the z scores obtained in step 4.

 9-4
The R values, like the z values obtained in step 4, represent interval-scale values for the stimuli, 

with higher values indicating stimuli judged to be better with respect to the attribute of interest. 

As seen in table 9-4, icon E cannot be assigned a scale value. This results from the fact that icon 

E was invariably placed in ranked 5. If a stimulus is placed in the same rank by all judges, it 

cannot be assigned a scale value using this procedure.

Table 9-5. p – z Conversion Table

p – z values 

p 

z

0.01 

-2.33 

0.02 

-2.05 

0.03 

-1.88 

0.04

-1.75

0.05

-1.64

0.06

-1.55

0.07

-1.48

0.08 

--1.41 

0.09 

-1.34 

0.10 

-1.28 

p 

z

0.11 

-1.23 

0.12 

-1.18 

0.13 

-1.13 

0.14

-1.08

0.15

-1.04

0.16

-0.99

0.17

-0.95

0.18 

-0.92 

0.19 

-0.88 

0.02 

-0.84 

p 

z

0.21 

-0.81 

0.22 

-0.77 

0.23 

-0.74 

0.24

-0.71

0.25

-0.67

0.26

-0.64

0.27

-0.61

0.28 

-0.58 

0.29 

-0.55 

0.30 

-0.52 

p 

z

0.31 

-0.50 

0.32 

-0.47 

0.33 

-0.44 

0.34

-0.41

0.35

-0.39

0.36

-0.36

0.37

-0.33

0.38 

-0.31 

0.39 

-0.28 

0.40 

-0.25 

p 

z

0.41 

-0.23 

0.42 

-0.20 

0.43 

-0.18 

0.44

-0.15

0.45

-0.13

0.46

-0.10

0.47

-0.08

0.48 

-0.05 

0.49 

-0.03 

0.50 

-0.00 

p 

z

0.51 

+0.03 

0.52 

+0.05 

0.53 

+0.08 

0.54

+0.10

0.55

+0.13

0.56

+0.15

0.57

+0.18

0.58 

+0.20 

0.59 

+0.23 

0.60 

+0.25 

p 

z

0.61 

+0.28 

0.62 

+0.31 

0.63 

+0.33 

0.64

+0.36

0.65

+0.39

0.66

+0.41

0.67

+0.44

0.68 

+0.47 

0.69 

+0.50 

0.70 

+0.52 

p 

z

0.71 

+0.55 

0.72 

+0.58 

0.73 

+0.61 

0.74

+0.64

0.75

+0.67

0.76

+0.71

0.77

+0.74

0.78 

+0.77 

0.79 

+0.81 

0.80 

+0.84 

p 

z

0.81 

+0.88 

0.82 

+0.92 

0.83 

+0.95 

0.84

+0.99

0.85

+1.04

0.86

+1.08

0.87

+1.13

0.88 

+1.18 

0.89 

+1.23 

0.90 

+1.28 

p 

z

0.91 

+1.34 

0.92 

+1.41 

0.93 

+1.48 

0.94

+1.55

0.95

+1.64

0.96

+1.75

0.97

+1.88

0.98 

+2.05 

0.99 

+2.33 

 0.995

+2.58 

 9-5
B. Torgerson’s Categorical Scaling Method

This scaling method is based on Torgerson’s Law of Categorical Judgment.3

 (Torgerson, 1962). 

While it involves more computational steps than the Choice Score Method, it also seems to 

reflect stronger theoretical foundations. For the raw data of table 9-1, the two scaling methods 

produce similar scores; however, we cannot conclude that the scale values will be the same in all 

cases. 

The method proceeds as follows: 

 3

 Torgerson’s Law of Categorical Judgment is a set of equations relating parameters of stimuli and category

boundaries to a set of cumulative proportions derived from the proportion of times each stimulus is judged to be in 

each category of a set of categories ordered with respect to a given attribute The complete form of the law is as

follows: 

( 2 ) ( 1,2.. ; 1,2.. ) 2 2 1/ 2 t g − sj = x jg σ j +σ g − rjgσ jσ g j = n g = m

where 

n = number of stimuli 

m+1 = number of categories 

sj = scale value of stimulus j

tg = mean location of the gth category boundary

σ j = discriminal dispersion of stimulus j

σ g = dispersion of the g

th category boundary 

rjg = correlation between momentary values associated with stimuli j and category boundary g

xjg = unit normal deviate corresponding to the proportion of times stimulus j is sorted below boundary g

In the solution procedure described, it is assumed that σj is constant, σg is constant, and rjg is constant for all values 

of j and g. 

Step 1. Prepare a matrix (matrix A) that 

indicates the frequency with which each 

stimulus (icon) is placed in each rank. For 

the raw data of table 9-1, matrix A is as seen 

in table 9-6. The rows of this matrix 

represent the stimuli and the columns, the 

ranks. In each column is the number of 

times a given icon received that rank. Icons 

are treated as j in the equations; ranks as g. 

For example, the element in the fourth row, 

third column (4) is the number of times icon 

D was placed in rank 3. 

Table 9-6. Matrix A

Rank

1 2 3 4 5

A 0 1 3 6 0

B 3 5 1 1 0

C 6 2 2 0 0

D 1 2 4 3 0

Ico

n

E 0 0 0 0 10

 9-6
Step 2. Obtain matrix B by identifying any 

elements of matrix A that are equal to the 

number of judges (nj) and removing the 

corresponding rows and columns from the 

matrix. For example, in matrix A of table 

9-6, we identify one element that is equal to 

10 (nj), and we delete the corresponding row 

and column (fifth row, and fifth column) to 

obtain matrix B of table 9-7. This step 

removes from the data matrix any stimuli 

that have been placed in the same rank by all 

judges. Such stimuli cannot be assigned an 

interval-scale value using this procedure, 

and their exclusion simplifies the 

computations. 

Step 3. Construct matrix C by cumulating 

the rows of matrix B from the left. For 

matrix B of table 9-7, matrix C is as seen in 

table 9-8. The first row of this matrix is 

computed as follows: 0, 0 + 1 = 1, 

0 + 1 + 3 = 4, 0 + 1 + 3 + 6 = 10. The 

elements in the last column should be equal 

to the number of judges. 

Step 4. Construct matrix D by dividing each 

element of matrix C by the rightmost 

element of the corresponding row, and then 

obtain row totals. For matrix C of table 9-8, 

matrix D is as seen in table 9-9. The first 

row of this matrix is computed as follows: 

0/10 = 0, 1/10 = 0.1, 4/10 = 0.4, 10/10 = 1. 

The row total of this row is 0 + 0.1 + 0.4 + 1 

= 1.5. 

Table 9-7. Matrix B

Rank

1 2 3 4

A 0 1 3 6

B 3 5 1 1

C 6 2 2 0

Ico

n

D 1 2 4 3

Table 9-8. Matrix C

Rank

1 2 3 4

A 0 1 4 10 

B 3 8 9 10 

C 6 8 10 10

Ico

n

D 1 3 7 10 

Table 9-9. Matrix D

Rank

1 2 3 4 Row 

Total 

A 0 0.1 0.4 1 1.5

B 0.3 0.8 0.9 1 3.0

C 0.6 0.8 1 1 3.4

Ico

n

D 0.1 0.3 0.7 1 2.1

 9-7
Step 5. Construct matrix E by ordering the 

rows of matrix D in decreasing magnitude of 

row totals, and leaving out the rightmost 

column. For the matrix D of table 9-9, 

matrix E is as seen in table 9-10. The row 

that corresponds to icon C has the highest 

row total (3.4), therefore, it is the first row 

of matrix E. Rows corresponding to icons 

B, D, and A follow in that order. 

Step 6. Construct matrix F, whose elements 

are equal to the z-scores (from table 9-5) of 

the corresponding elements of matrix E. For 

matrix E of table 9-10, matrix F is as seen in 

table 9-11. The element in the second row, 

third column (1.28) is the z-score 

corresponding to 0.9 in table 9-5. The 

elements of this matrix will be negative for 

all proportions below 0.5, and positive for 

all proportions above 0.5. Any cells of 

matrix E that contain proportions of 0 or 1 

cannot be transformed into a z-score, and are 

left vacant. 

Step 7. Construct matrix G, which shows the 

differences in the rows of matrix F, and 

obtain row means. The first row of matrix G 

is computed by subtracting row 2 of matrix 

F from row 1 of matrix F; the remaining 

rows are computed similarly. For matrix F 

of table 9-11, matrix G is as seen in table 

9-12. The first row of matrix F is 

constructed as follows: 0.25 – (–0.52) 

= 0.77, 0.84 – 0.84 = 0, vacant. In 

computing the row means, vacant cells are 

excluded. For instance, the mean of row 1 

in table 9-12 is (0.77 + 0)/2 = 0.39. 

Table 9-10. Matrix E

Rank

1 2 3

C 0.6 0.8 1

B 0.3 0.8 0.9

D 0.1 0.3 0.7

Ico

n

A 0 0.1 0.4

Table 9-11. Matrix F

Rank

1 2 3

C 0.25 0.84 –

B -0.52 0.84 1.28

D -1.28 -0.52 0.52

Ico

n

A – -1.28 -0.25

Table 9-12. Matrix G

Rank

1 2 3 Row 

Mean 

C-B 0.77 0 – 0.39

B-D 0.76 1.37 0.76 0.96

Ico

n

D-A – 0.76 0.78 0.77

 9-8
Step 8. Compute interval-scale values for the stimuli by listing the stimuli in the same order as 

in matrix F, assigning a score of 0 to the last stimulus in the list, and cumulating toward the top 

using the row means of matrix G. For matrix G of table 9-12, the scale values are computed as 

shown in table 9-13. The first column lists the icons in the same order they were listed in matrix 

F of table 9-11; the second column lists the row means of matrix G of table 9-12. We first assign 

a scale value of 0 to icon A. We then compute the scale value of icon D as follows: 

0+0.77 = 0.77. Scale values for icons B and C are assigned in a similar manner. 

Table 9-13. Step 8: Assigning Interval-Scale Values

Icon

Row Means of Matrix G 

(from table 9-12) Scale Value

C 0.39 (C-B) 0 + 0.77 + 0.96 + 0.39 = 2.12

B 0.96 (B-D) 0 + 0.77 + 0.96 = 1.73

D 0.77 (D-A) 0 + 0.77 = 0.77

A 0

Assign

scale 

values by

cumulating

from

bottom to

top 

Note that higher scale values indicate better (i.e., more appropriate) icons. Note also that we 

cannot assign a scale value for icon E, but we know that its score would be lower than the scores 

of all other icons, as it was placed in rank 5 by all judges. 

4. CONDUCTING A TEST OF SIGNIFICANCE

Using the methods discussed so far, we might obtain a composite rank order for the stimuli with 

no ties, and a different interval-scale score for each stimulus. Does that mean that the stimuli are 

truly different from each other with respect to the attribute of interest? Not necessarily. To 

answer this question, we need to perform a test of significance. A test of significance allows us 

to determine, with a specified risk of error, whether the observed difference is really meaningful, 

or whether we might expect the same difference to occur merely because of chance factors. 

On rank-order data from a group of judges (e.g., the raw data of table 9-1), we can conduct a 

significance test based on Friedman Rank Sums to determine whether there are or are not real 

differences between the stimuli. A detailed explanation of this statistical test is beyond the scope 

of this tutorial, but the general outline is as follows: 

1. Compute a summary score from the data. This summary score reflects the differences 

between the ranks assigned to each stimulus. The more different the ranks of each 

stimulus, the greater will be this summary score. 

2. Compare this summary score to a criterion value. This criterion indicates how big the 

summary score can get if there are no true differences between the stimuli. The criterion 

will vary depending on the number of observations in the data set and the risk of error

one is willing to take. If the summary score is greater than the criterion, conclude that the 

stimuli are truly different with respect to the attribute of interest. 

 9-9
Using the Friedman test, we can test the equivalence of all stimuli, or perform pairwise 

comparisons. For a detailed explanation of this statistical test, readers should refer to a text on 

nonparametric statistical methods (e.g., Hollander & Wolfe, 1973). The Friedman test is also 

available in several commercial statistical software packages.

SUMMARY 

We have discussed several methods of analyzing rank order data. These are summarized in table 

9-14. This table provides a guide for the designer in determining which method(s) would be 

appropriate for the design problem at hand. 

Table 9-14. Summary of Methods Discussed for Analyzing Rank Order Data

Method Outcome Computational Complexity 

Compute sum of assigned ranks Provides a composite ranking Simple

Compute mean ranks Provides a composite ranking;

will somewhat agree with the 

spacing of the composite ranks 

Simple 

Compute interval-scale values for the stimuli 

using one of the following:

 1) Choice score method 

 2) Torgerson’s categorical scaling method

Provides an indication of

relative differences between the 

stimuli 

Requires a series of simple 

computations 

Conduct a test of significance Provides evidence for 

concluding, with a specified risk 

of error, that there are or are not 

real differences between the 

stimuli 

Complex, can be performed 

using statistical software 

packages 

References:

1. Engen, T. (1971). Psychophysics: Scaling methods. In J. W. Kling and L. A. Riggs (Eds.), 

Woodworth and Schlosberg’s experimental psychology (3rd. ed.) (pp. 47-86). New York: 

Holt, Rinehart, & Winston, Inc. 

2. Hollander, M., and Wolfe, D. A. (1973). Nonparametric statistical methods. New York: J. 

Wiley & Sons, Inc. 

3. Torgerson, W. S. (1962). Theory and methods of scaling. New York: J. Wiley & Sons, Inc. 

 9-10 
TUTORIAL 2: PROVIDING SUBJECTS WITH CONTEXT DURING ICON 

EVALUATIONS 

This tutorial provides some guidance and examples of ways to provide appropriate context to 

experimental subjects during comprehension evaluations of candidate icons. In real-world 

driving, icons are presented in the context of certain in-vehicle capabilities and driving 

circumstances. As such, evaluations of in-vehicle icons should include a description of the 

context in which icons will be presented and used. However, icon evaluations should avoid 

providing either too little or too much context to experimental subjects. If too little context is 

provided, unrealistically low comprehension scores may result because the subjects may be 

unable to connect a visual icon with the many possible icon meanings. If too much context is 

provided, unrealistically high comprehension scores may result because the subjects have been 

cued for a certain response by the specificity of the context. Both these extremes should be 

avoided. 

The context provided to subjects should describe the: (1) general capabilities of the in-vehicle 

system that will be used to present the icons and (2) general driving circumstances associated 

with the presentation of the icon by the in-vehicle system. For example, an evaluation of an icon 

intended to warn drivers of a problem with the passive restraint system on their vehicle might 

provide the following “system capabilities” information to subjects: 

Our purpose is to investigate issues related to the use of graphical icons in 

the in-vehicle environment. Recent advances in automotive technology 

have allowed the development of various In-Vehicle Information Systems

(IVIS) that present a wide range of trip, vehicle, and safety information to 

drivers. Much of this information will be provided to drivers through color 

displays located on the instrument panel or center console of the vehicle. 

These display systems might present information such as: 

• Adaptive Cruise Control: An improved cruise control system that maintains adequate 

spacing between the driver’s car and the vehicle ahead. 

• Augmented Signage: System that displays regulatory and road condition icons for the 

road on which the driver is presently driving. Icons would be similar to the signs posted 

along the roadside. 

• Collision Avoidance System: On-board sensor and display systems that warn the driver 

of an impending collision with another vehicle or object, vehicle lane departure, and 

other motion-based hazards. 

• Motorist Services: Information that provides an in-vehicle “Yellow Pages” function to 

drivers. This directory would present information regarding the availability and 

locations of motorist services such as gas stations, restaurants, hotels, or recreational 

activities. 

 9-11 
• Trip Navigation: Information that provides the driver with route assistance and trip 

planning. This includes driving directions, cautions about certain routes, current traffic 

conditions, road construction, or weather updates. 

• Vehicle Condition Monitoring: Device that informs the driver of problems with the 

vehicle or vehicle systems (oil, tire pressure, engine, etc.).

The following “driving circumstances” information could be provided to drivers: 

Figure 9-1. Sample Icon 

You have just started your car. 

A group of icons appears on your In-Vehicle Information System, including this icon. 

What do you think this icon means?

Similarly, in the context of evaluating comprehension for a specific Motorists Services icon, the 

following “driving circumstances” information could be provided: 

Figure 9-2. Motorists Services Icon

You are driving on a highway. 

This icon appears on the In-Vehicle Information System installed in your car. 

What do you think this icon means?

 9-12 
CHAPTER 10: SENSORY MODALITY DESIGN TOOL 

This section of the guidelines provides designers of in-vehicle icons with a design tool that can 

help determine the most appropriate display modality for presenting in-vehicle information 

elements. This tool was originally developed as part of the preliminary assessment of symbols 

and is described in more detail in Lee et al. (1998). The tool was generated based on an 

examination of the general design rules found in relevant literature. 

Very Low Medium High Very

Visual

Auditory

Tactile

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1. What is the degree of

urgency of the message?

2. To what degree might

the message be referred

to again later?

3. What is the overall

level of complexity of

the message?

4. To what degree does

the message deal with a

future action in time?

5. To what degree does

the message refer to

locations in space?

IVIS Message:

Other Relevant Factors:

Visual

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Visual Auditory Tactile

1. What is the degree of

urgency of the message?

2. To what degree might

the message be referred

to again later?

3. What is the overall

level of complexity of

the message?

4. To what degree does

the message deal with a

future action in time?

5. To what degree does

the message refer to

locations in space?

IVIS Message:

Other Relevant Factors:

Questions: Very Low Medium High Very Visual Auditory Tactile

Figure 10-1. Sensory Modality Design Tool 

The design tool asks designers to respond to several questions independently. For each question, 

their response will range from “very low” to “very high.” Each response is associated with a 

point value for the three modalities (visual, auditory, and tactile). After all five questions have 

been answered, the point values are totaled for each of the modalities. The steps a designer must 

complete to use this design tool are summarized below and shown in detail in the figure on the 

following page. 

 10-1
Step 1: Identify and Define Driver Message. 

Step 2: Determine Appropriate Response to the Question and Circle Scores. 

Step 3: Transpose Scores to Visual, Auditory, and Tactile Columns. 

Step 4: Complete Steps 2 and 3 for Questions 2 through 5. 

Step 5: Total Columns. 

Visual

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1. What is the degree of

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2. To what degree might

the message be referred

to again later?

3. What is the overall

level of complexity of

the message?

4. To what degree does

the message deal with a

future action in time?

5. To what degree does

the message refer to

locations in space?

IVIS Message:

Other Relevant Factors:

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16 13 10

Step 4:

Complete Step 2 and 

Step 3 for Questions 

2 through 5

Step 3:

Transpose Scores to

Visual, Auditory, and

Tactile Columns

Visual

Auditory

Tactile

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Low High

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1. What is the degree of

urgency of the message?

4

1

1

Complete these steps for all five questions:

Step 1: Identify and Define Driver Message

Step 2:

Determine Appropriate

Response to the 

Question and Circle

Scores

Visual

Auditory

Tactile

Very Low Medium High Very

Low High

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1. What is the degree of

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Questions:

Questions:

Questions:

Step 5:

Total Columns

Layover time between travel segments (evaluate and plan)

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1. What is the degree of

urgency of the message?

2. To what degree might

the message be referred

to again later?

3. What is the overall

level of complexity of

the message?

4. To what degree does

the message deal with a

future action in time?

5. To what degree does

the message refer to

locations in space?

IVIS Message:

Other Relevant Factors:

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16 13 10

Step 4:

Complete Step 2 and 

Step 3 for Questions 

2 through 5

Step 3:

Transpose Scores to

Visual, Auditory, and

Tactile Columns

Visual

Auditory

Tactile

Very Low Medium High Very

Low High

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Visual Auditory Tactile

1. What is the degree of

urgency of the message?

4

1

1

Complete these steps for all five questions:

Step 1: Identify and Define Driver Message

Step 2:

Determine Appropriate

Response to the 

Question and Circle

Scores

Visual

Auditory

Tactile

Very Low Medium High Very

Low High

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Visual Auditory Tactile

1. What is the degree of

urgency of the message?

Questions:

Questions:

Questions:

Step 5:

Total Columns

Layover time between travel segments (evaluate and plan)

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16 13 10

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Visual Auditory Tactile

1. What is the degree of

urgency of the message?

2. To what degree might

the message be referred

to again later?

3. What is the overall

level of complexity of

the message?

4. To what degree does

the message deal with a

future action in time?

5. To what degree does

the message refer to

locations in space?

IVIS Message:

Other Relevant Factors:

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Visual Auditory Tactile

16 13 10

Step 4:

Complete Step 2 and 

Step 3 for Questions 

2 through 5

Step 3:

Transpose Scores to

Visual, Auditory, and

Tactile Columns

Visual

Auditory

Tactile

Very Low Medium High Very

Low High

4

1

1

3

2

2

2

3

3

1

4

4

1

5

5

Visual Auditory Tactile

1. What is the degree of

urgency of the message?

4

1

1

Complete these steps for all five questions:

Step 1: Identify and Define Driver Message

Step 2:

Determine Appropriate

Response to the 

Question and Circle

Scores

Visual

Auditory

Tactile

Very Low Medium High Very

Low High

4

1

1

3

2

2

2

3

3

1

4

4

1

5

5

Visual Auditory Tactile

1. What is the degree of

urgency of the message?

Questions:

Questions:

Questions:

Step 5:

Total Columns

Layover time between travel segments (evaluate and plan)

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Low High

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Figure 10-2. Steps for Using the Sensory Modality Design Tool 

 10-2
Determining the most appropriate modality is not always as easy as selecting the one that 

receives the highest point value. In cases where two modalities receive high scores (15 or 

greater), it is suggested that the information be presented using some combination of the two. 

This will reflect the fact that both modalities are necessary to adequately present the information. 

In cases where two modalities receive the same score or they are only one point apart, it is 

suggested that the information be presented using either of the two modalities. In all other cases, 

the modality that receives the highest score is the suggested mode of presentation for that piece 

of information. Decisions regarding which one to use may be based on additional information 

regarding context or display constraints. If, however, two modalities receive scores that are both 

higher than 15 and only one point apart, then the benefits of using both modalities outweigh 

other design considerations and the information should be presented by combining the two 

modalities, instead of choosing between them. By prioritizing the rules below, the designer will 

know which one to use in cases where more than one is applicable. The rules for determining 

the most appropriate modality can be summarized as follows. 

Scores for each modality have been obtained using

the design tool described in figures 10-1 and 10-2.

Design Decision

A combination of the two

modalities should be used

to display the information

(e.g., auditory and visual)

A design decision must be

made regarding which of

the two modalities is most 

appropriate (e.g., auditory

or visual)

The modality receiving the

highest score should be used

to display the information

(e.g., auditory only)

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive

identical scores or scores

within 1 point of each other?

Did two modalities receive

identical scores or scores

within 1 point of each other?

NO

YES

YES

NO

YES Did one modality receive the

highest score (2 or more points

above the other modalities)?

Did one modality receive the

highest score (2 or more points

above the other modalities)?

Scores for each modality have been obtained using

the design tool described in figures 10-1 and 10-2.

Design Decision

A combination of the two

modalities should be used

to display the information

(e.g., auditory and visual)

A design decision must be

made regarding which of

the two modalities is most 

appropriate (e.g., auditory

or visual)

The modality receiving the

highest score should be used

to display the information

(e.g., auditory only)

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive

identical scores or scores

within 1 point of each other?

Did two modalities receive

identical scores or scores

within 1 point of each other?

NO

YES

YES

NO

YES Did one modality receive the

highest score (2 or more points

above the other modalities)?

Did one modality receive the

highest score (2 or more points

above the other modalities)?

Scores for each modality have been obtained using

the design tool described in figures 10-1 and 10-2.

Design Decision

A combination of the two

modalities should be used

to display the information

(e.g., auditory and visual)

A design decision must be

made regarding which of

the two modalities is most 

appropriate (e.g., auditory

or visual)

The modality receiving the

highest score should be used

to display the information

(e.g., auditory only)

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive 

scores of 15 or greater?

Did two modalities receive

identical scores or scores

within 1 point of each other?

Did two modalities receive

identical scores or scores

within 1 point of each other?

NO

YES

YES

NO

YES Did one modality receive the

highest score (2 or more points

above the other modalities)?

Did one modality receive the

highest score (2 or more points

above the other modalities)?

Figure 10-3. Rules for Determining Display Modality 

 10-3
In the above flow diagram, the designer is asked to address each rule in the order of its priority. 

For example, if the auditory modality received a score of 17 and the visual scores 16, the first 

question a designer would ask is “Did two modalities receive scores of 15 or greater?” Since the 

answer is “yes,” the design decision states that “a combination of the two modalities should be 

used to display the information.” However, if the auditory modality had received a score of 14 

and the visual a score of 15, the answer to that first question would be “no.” In this case, a 

designer would then proceed to the next question “Do the two modalities receive identical scores 

or scores within one point of each other?” Since the answer is “yes,” the design decision states 

that “a decision must be made regarding which of the two modalities is most appropriate.” In the 

last case (i.e., the auditory modality receives a score of 12 and the visual a score of 15), the 

answer to both the first and the second question would be “no.” Therefore, the designer would 

proceed to the third question and the subsequent design decision, which would be to present the 

modality that had received the highest score.

 10-4
CHAPTER 11: LIST OF EQUATIONS 

Determining the Appropriate Luminance Uniformity within an Icon 

Page 3-2 

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

(1)

where: Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

Percent Element

Nonuniformity

=

(Luminancemin ) – (Luminancemax )

(Luminancemax )

Luminancemin = the smaller luminance value

Luminancemax = the greater luminance value

Determining the Appropriate Contrast within an Icon

Page 3-4 

Here, we define contrast as a ratio between maximum and minimum luminance values, or: 

Contrast ratio = Luminance max ____________________ (2) 

 Luminance min

 where: 

 Luminance max = luminance emitted by the area or element of greatest intensity. 

 Luminance min = luminance emitted by the area or element of least intensity 

Determining the Appropriate Size of Icon Components

Page 3-6 

Use These Formulas for Calculating These Unknowns If Known Visual Angle Symbol Height Distance 

Distance and 

Symbol Height 

(3) or

(4) 

– –

Distance and 

Visual Angle 

– 

(5)

– 

Visual Angle and 

Symbol Height 

– –

(6) 

Arctan Symbol Height

Distance

Distance

3438 (Height) ÷ 60 Distance3438 (Height)

Distance

3438 (Height) ÷ 60

Distance H [Tangent (Visual Angle)]

Tangent (Visual Angle)

Symbol Height

where: Symbol Height = the height of the symbology

Distance = distance from viewer’s eyepoint to the display 

Visual Angle = angle in degrees 

Height and Distance use the same unit of measure (e.g., meters, yards, etc.)

 11-1
The Effects of Color on Icon Legibility

Page 3-10

where:

∆E (CIE Yu' v' = the color contrast metric

∆Y = difference in luminance between text (symbology) and background

Ym = the maximum luminance of text (symbology) or background

∆u' = difference between u' coordinates of text (symbology)

and background (per the 1976 CIE UCS; see note below)

∆v' = difference between v' coordinates of text (symbology)

and background (per the 1976 CIE UCS; see note below)

NOTE: The constants 155, 367, and 167 in equation 7 are empirically derived weights (reference 1).

∆E (CIE Yu' v') = [( ) ] 155 ∆Y

Ym

2

+ (367 ∆u')

2 + (167 ∆v') 2

0.5

(7)

where:

∆E (CIE Yu' v' = the color contrast metric

∆Y = difference in luminance between text (symbology) and background

Ym = the maximum luminance of text (symbology) or background

∆u' = difference between u' coordinates of text (symbology)

and background (per the 1976 CIE UCS; see note below)

∆v' = difference between v' coordinates of text (symbology)

and background (per the 1976 CIE UCS; see note below)

NOTE: The constants 155, 367, and 167 in equation 7 are empirically derived weights (reference 1).

∆E (CIE Yu' v') = [( ) ] 155 ∆Y

Ym

2

+ (367 ∆u')

2 + (167 ∆v') 2

0.5

(7)

Perceived Urgency of Auditory Signals 

Page 6-16

Example of Using Steven’s Power Law for Producing Urgency Exponents 

(see references 2 and 3 for more detailed explanations and examples) 

 S = kOm (8) 

Log10 (O)

Log10 (S)

m = the slope

of the line of

best fit

k = the intercept of

the line of best fit

1.5

1.55

1.6

1.65

1.7

1.75

1.8

1.85

2.7 2.8 2.9 3 3.1 3.2

Where:

S = Subjective value of Perceived Urgency rating

(note: range of subjective scale was 0 to 100.)

O = Objective value

 11-2
Timing of Auditory Navigation Information 

Page 6-20

Equations for Determining the Appropriate Timing of an Instruction 

Preferred Maximum Distance = 144 meters

Preferred Minimum Distance = 93 meters

Ideal Distance = 116 meters

Vehicle Speed =

48 kph (30 mph)

EQUATIONS1

= (Speed x 1.637) + 14.799

= (Speed x 1.973) + 21.307

= (Speed x 2.222) + 37.144

Preferred Minimum Distance (9)

Ideal Distance (10)

Preferred Maximum Distance (11)

Example of the Suggested Timing for Navigational Information

1 where speed is in km/h and distances are in meters

50 m

100 m

150 m

Preferred Maximum Distance = 144 meters

Preferred Minimum Distance = 93 meters

Ideal Distance = 116 meters

Vehicle Speed =

48 kph (30 mph)

EQUATIONS1

= (Speed x 1.637) + 14.799

= (Speed x 1.973) + 21.307

= (Speed x 2.222) + 37.144

Preferred Minimum Distance (9)

Ideal Distance (10)

Preferred Maximum Distance (11)

Example of the Suggested Timing for Navigational Information

1 where speed is in km/h and distances are in meters

50 m

100 m

150 m

 11-3
CHAPTER 12: GLOSSARY 

ACC 

Appropriateness 

Ranking Test 

ASR 

ATIS 

Auditory signals 

Auditory icons 

Augmentation of icons 

with auditory 

information

Automatic Speech 

Recognition (ASR) 

systems 

CAS 

CIE 

Color coding 

Composition of an icon 

Automated Cruise Control. 

Refers to a test to screen the candidate symbols generated 

during the Production Test and to select the best for further 

testing. 

Automatic Speech Recognition. 

Advanced Traveler Information Systems. 

Refers to simple tones, earcons, auditory icons, or speech 

messages. 

These are familiar environmental sounds (iconic, 

metaphorical, and symbolic) that intuitively convey 

information about the object or action that they represent 

To make the message clearer or more salient, some type of 

auditory signal is included with an icon. 

Devices that recognize human speech and, in an in-vehicle 

context, treat speech commands as inputs to an IVIS device. 

Currently, ASR is viewed as an enabling technology in 

intelligent transportation system (ITS) development, allowing 

the driver to interact with the IVIS device while maintaining 

his/her eyes on the road and hands on the wheel. 

Collision Avoidance System. 

Commission Internationale de l’Eclairage (International 

Lighting Commision).

Refers to the use of chromaticity to differentially identify

items in a display systematically. The categories used to 

color code objects on a display depend upon the tasks 

required of the operators. 

Composition of an icon refers to the parts that comprise an 

icon. 

12-1
Comprehension/ 

Recognition Test

Contrast 

Conveying the effect of

actions with icons 

Conveying system status 

with icons 

Conveying urgency with 

icons 

CRT 

CVO 

CVO-specific icons 

dB 

Development process for 

in-vehicle icons 

Display modality 

DOT 

DVI 

Earcons

This test is an evaluation technique that provides a means to 

determine which of a number of candidate icons/symbols for 

a concept is best understood by a sample of subjects who 

represent the user population. 

The relationship between the luminance of a symbol and the 

luminance of the symbol’s background. 

Refers to the ability of an icon to help the driver anticipate the

effect of selecting a particular system function or option. 

Refers to changing icon appearance to convey changes in the 

system state.

Urgency is conveyed by adjusting icon characteristics to 

reflect the appropriate level of urgency of the situation. 

Cathode Ray Tube. 

Commercial Vehicle Operations. 

Icons that relate to commercial vehicle operations. 

Decibel, a unit for expressing relative difference in power; 

usually between acoustic or electrical signals, equal to ten 

times the common logarithm of the ratio of the two levels. 

This process reflects the specific needs, goals, and constraints 

associated with individual design efforts, providing important 

information that will increase the effectiveness and utility of

icons. 

Refers to decisions regarding the use of visual, auditory, or 

haptic stimuli (or some combination of these three modes) to 

inform, alert, or warn the driver of some condition or 

situation. 

Department of Transportation. 

Driver-Vehicle Interface. 

Auditory signals that present information through musical 

tones that can be used in structured combinations to create 

auditory messages. 

12-2
Evaluation of in-vehicle 

icons 

FHWA 

Filtering sign 

information

fL 

Flash rate 

Flashing icons 

FMVSS 

Font segments 

FOV 

Grouping icons 

Guideline format 

HUD 

Hz

Icon 

The process of determining whether an icon, or an integrated 

set of icons, meets specific criteria in areas such as legibility, 

recognition, interpretation, and driver preferences. 

Federal Highway Administration. 

Refers to allowing the driver to select the on-road signage 

they would like to receive in-vehicle. The driver will be able 

to filter both notification and guidance sign information. 

However, regulatory sign information will be presented to the

driver regardless of preference. 

Foot lambert. 

The rate at which a signal alternates between an illuminated 

and a non-illuminated state. 

Icons that flash on and off in a predetermined on/off cycle. 

Federal Motor Vehicle Safety Standards. 

Refers to electronic displays in which characters are formed 

by illuminating discrete segments within a basic symbol 

pattern. The majority of electronic displays using this 

technique employ 7-segment patterns to generate numerals 

(e.g., digital speedometers and clocks); however, 14-segment 

and 16-segment patterns are also available for the generation 

of complete alphanumeric sets. 

Field-of-View. 

Grouping facilitates icon identification as a set of related 

messages or similar commands. 

The method used to present guidelines to system designers 

and developers. 

Head-Up Display. 

Hertz, a unit of frequency equal to one cycle per second. 

A visual representation or image used to symbolize an object, 

action, or concept. 

12-3
Icon comprehension 

Icon interpretation 

enhanced with color 

Icon interpretation 

enhanced with shape 

Icon interpretation 

enhanced with text labels 

Icon legibility 

Identification time task

Information units 

ISO 

ITS 

IVIS 

LCD 

Level of detail 

Level of realism 

Luminance uniformity 

Refers to the perceptual and cognitive processes by which 

users interpret the meaning of an icon. 

Refers to the manner in which color can highlight information 

and enhance drivers’ interpretation of the icon. 

Refers to the manner in which the shape of an icon’s outside 

edge or border can call attention to the hazard level being 

communicated. 

Refers to the manner in which the content of text labels can 

affect the comprehension and interpretation of an icon. 

The reflection of the relationship between the driver, the icon, 

and the environment 

After being shown slides of traffic signs (in both text and 

symbol format) and being asked to identify verbally the 

message that is being presented, the subject’s response time is 

recorded as identification time. 

Describe the amount of information presented in terms of key 

nouns and adjectives contained in a message. 

International Organization for Standardization. 

Intelligent Transportation Systems. 

In-Vehicle Information System. 

Liquid crystal display. 

Refers to the amount of detail necessary for recognition of a 

symbol. 

Refers to the relationship between the portrayed object or

concept and the graphic means used to represent that object or

concept. 

Refers to the consistency of luminance values across an icon. 

12-4
Matching Test 

MUTCD 

Perceived urgency of 

auditory signals 

Perceptual principles of

icon design

Production test 

Prohibitive symbols 

Rating task

Reaction time task

Relationship between invehicle icons and 

roadway signs 

R&D 

SAE 

When the best or most appropriate design for a particular 

symbol has been determined, this test is used to examine how 

well that symbol will work within a set and whether the many 

symbols within the set can be discriminated from one another 

without confusion. 

Manual on Uniform Traffic Control Devices. 

Refers to the subjective impression of urgency that a signal 

gives to the person hearing it. 

Refers to design recommendations based solely on the visual 

characteristics of the icon without reference to its intended 

function or meaning. 

An icon evaluation approach in which a broad range of 

candidate symbols for a concept or referent (i.e., in-vehicle 

message) is generated. This approach is used when no 

symbols for a given message exist. 

Icons that present a specific action and communicate that the 

action should be avoided. 

Determines the degree to which a symbol suggests or 

communicates its designated name. 

After a subject views a referent and then is shown a slide of 

one of the symbols, the subject is asked if they are the 

“same”; the amount of time the subject takes to make the 

response is recorded as reaction time. 

Refers to the correspondence or consistency between these 

two forms of presenting information to the driver. 

Information might be presented on roadway signs alone, on 

the IVIS alone, or on both display media. 

Research and Development. 

Society of Automotive Engineers. 

12-5
Selection of colors for 

coding visual displays

Semantic differential 

method 

Sensory modality for 

presenting IVIS messages 

Simple tones 

Size of icon components 

SNR 

Speech messages 

Symbol color 

Refers to the use of different colors to either bring 

information to the attention of a driver or to aid the driver in 

distinguishing between items on a display. Color coding may 

be used to make absolute or relative discriminations, and 

should be used in a way that is redundant with other coding 

dimensions (e.g., shape, size, brightness). 

After subjects rate symbols on 12 different adjective pairs, 

(e.g., weak-strong, strange-familiar), a factor analysis is 

performed to evaluate the results. A modified method uses 

adjective pairs more specific and relevant to designers (e.g., 

balanced-unbalanced, confusing-clear, etc.). 

Refers to the display modality most appropriate for presenting 

in-vehicle information to the driver. Almost all the literature 

on this topic suggests that operator performance can be 

improved by combining auditory and visual messages. These 

channels should be used together to provide either redundant 

or complimentary cues to the driver whenever possible. 

However, it is also important to know the advantages and 

disadvantages of using each of these modalities independent 

of one another so that when designers are faced with a choice, 

they can choose the modality that facilitates driver decision 

making and performance. 

Auditory signals that present information through the use of 

single or grouped frequencies presented simultaneously. 

Refers to the visual angle subtended (at the driver’s eye) in 

minutes of arc, by either the symbol or the text that comprises 

an icon. 

Signal-to-Noise Ratio. 

Auditory signals that present information through voice 

messages that add information beyond pure sound. 

The perception of color is derived from variations in the 

wavelength or spectral composition of light. Color perception 

can be described in terms of three psychological dimensions: 

hue, saturation, and brightness. Hue is related to the 

dominant wavelength of the stimulus; saturation is somewhat 

more loosely related to the spectral bandwidth of the stimulus; 

and brightness is related to the luminance of the stimulus. 

12-6
 Symbol font 

Symbol height 

Symbol spacing 

Symbol strokewidth-toheight ratio 

Symbol versus text 

presentation of IVIS 

messages 

Symbol width-to-height 

ratio 

Text labels

Timing of auditory 

navigation information 

Refers to the geometrical characteristics or style of

symbology. Design goals for symbol font are to avoid 

extensive flourishes and embellishments of the symbols. 

Refers to the vertical distance between the top and bottom

edges of a number or unaccented letter. Since IVIS devices 

can be used at a broad range of display distances, symbol 

height is best defined and specified as the visual angle 

subtended by the symbology (at the driver’s eye) in minutes 

of arc. 

Refers to the horizontal space between adjacent characters on 

a display. Symbol spacing is often expressed as the ratio of 

space-between-characters to symbol-height (space-to-symbolheight ratio). 

Refers to the ratio of the symbol stroke thickness to symbol 

height. 

Refers to the style and format of in-vehicle visual messages. 

A key IVIS design issue is presenting information to the 

driver so that it is not distracting and is easily understood. 

Symbols or icons are increasingly used in the design of 

electronic devices under the assumption that they are 

preferable to text (e.g., “a picture is worth a thousand 

words”). However, if drivers are unfamiliar with the symbol 

or if the symbol is not intuitive, it may be less effective than a

corresponding text message when used in an IVIS device. 

Refers to the ratio of the width to the height of the 

symbology. 

Words or phrases, as well as all other numerical and character 

symbols, provided as part of an icon that act to define, 

enhance, or clarify its meaning. 

Refers to the time or distance at which the in-vehicle 

navigation system should present an auditory instruction to 

the driver before an approaching navigation maneuver (e.g., a 

required turn). 

12-7
Types of icons 

UCS 

User Interface design 

Visual angle 

VDT 

VFD 

Ways to use icons 

When to use icons 

Refers to the classification of a particular icon based upon its 

resemblance to the message or referent. 

Uniform Chromaticity Scale, a scale, wherein the units of 

color difference that are judged to be equally different, are 

separated by nearly equal distance. 

Refers to the system design characteristics of a computerbased system that includes the screen layout and format, 

selection of icons, use of borders and windows, control 

selection and placement, and the procedures and “rules” that 

define transactions between the system and the user. 

The angle formed by two rays of light, or two straight lines 

drawn from the extreme points of an object to the center of 

the eyes. 

Visual Display Terminal. 

Vacuum Fluorescent Displays. 

Refers to the wide variety of options for using an icon to 

facilitate interaction with an in-vehicle information system

(IVIS). 

Refers to the criteria and issues that should be considered 

when determining whether an icon is the appropriate display 

element to use for an in-vehicle message. 

12-8
13-1 

 

CHAPTER 13: ACKNOWLEDGMENTS 

These human factors design guidelines for in-vehicle display icons are the product of nearly 5 

years of investigation into human factors design issues and driver requirements for in-vehicle 

icons and symbols. Although four authors are identified with this document, development of 

these preliminary guidelines has required the participation of many dedicated individuals. 

In particular, the authors would like to express their sincere gratitude to Dr. Tom Granda, our 

current FHWA Contracting Officer’s Technical Representative (COTR), for this project, as well 

as to Chris Monk, Maureen Hunter, and Ron Hoffman of SAIC for their tireless assistance 

during the conduct of this project. The direction, feedback, and advice provided by our 

FHWA/SAIC colleagues on this effort have been both timely and invaluable. 

We are also grateful for the direct assistance in the development of this handbook provided by 

Dr. Steve Casey, of Ergonomics System Design, Inc., and by our colleague, Ozgur Simsek. Dr. 

Casey was responsible for much of the development of the Sensory Modality Design Tool 

presented in chapter 10, while Ms. Simsek wrote most of the evaluation/statistical tutorial 

presented in chapter 9. 

We give additional thanks to graduate assistants Dawn Marshall, Andrea Tawil, Emily Wiese, 

and Mahesh Chandramouli of The University of Iowa, and to Elizabeth Mitchell, a former 

graduate assistant here at Battelle. Each of these individuals spent countless hours searching the 

internet and other commercial and government sources for potential icons and symbols to be 

included in the icon collection. Also, Kristi Schmidt of the University of Iowa contributed to the 

Icon research conducted during a summer internship at Battelle; her assistance is greatly 

appreciated. 

We would also like to thank our support staff, Mary Winter, Sharon Groves and Judy Panjeti, for 

their hard work and resourcefulness during the development of the guidelines. 

We owe a special thanks and debt of gratitude to the 38 researchers, designers, and developers of 

transportation systems who agreed to be members of our Project Working Group1

 and who 

volunteered their time to help make this guideline handbook more relevant and useful. We 

greatly appreciate all the time, expertise, and insight this talented group of people has shared 

with us during the conduct of his project. Specifically, we wish to thank: 

1

 List includes both current and past Working Group members. 
13-2 

Linda Angell 

General Motors Corporation 

Mike Campbell 

National Weather Service, Flagstaff

Cher Carney 

Battelle Human Factors Transportation Center 

Peter Chin 

Microsoft

Mark Cummings-Hill 

Delphi/Delco Electronics Systems

David G. Curry 

Packer Engineering, Inc. 

Stuart DeSpain 

Microsoft 

James P. Foley, Ph.D. 

MitreTek Systems, Inc. 

Thomas M. Granda, Ph.D. (FHWA COTR) 

Federal Highway Administration 

Barry Grant 

Ford Motor Company

Ronald B. Hoffman, Ph.D. (SAIC) 

Federal Highway Administration

David Hoffmeister 

Ford Motor Company

Maureen L. Hunter 

Avia Technology

Steven K. Jahns 

PACCAR Technical Center

Barry H. Kantowitz, Ph.D. 

University of Michigan Transportation 

Research Institute

Rick Karbowski 

Ford Motor Company 

Raymond J. Kiefer 

General Motors Corporation 

Chris Kirn 

DaimlerChrysler Research and Technology 

James A. Kleiss 

Johnson Controls, Inc.

Ken Kobetsky 

American Association of State Highway and 

Transportation Officials 

John D. Lee 

University of Iowa 

Eddy Llaneras 

Westat, Inc. 

Marvin McCallum, Ph.D. (Project Task Leader) 

Battelle Human Factors Transportation Center 

Christopher Monk (SAIC) 

Office of Health CareRegulation, National 

Highway Traffic Safety Administration 

Mark Ohashi 

Toyota Technical Center, USA

Colleen Page 

Microsoft

Joel B. Richman (Project Task Leader) 

Battelle Human Factors Transportation Center 

Gary L. Rupp 

Ford Motor Company
13-3 

Tina Brunetti Sayer 

Visteon Automotive Systems, ETC

Colleen Serafin 

Johnson Controls, Inc.

Valerie K. Sims 

University of Central Florida 

Marc Todd 

Microsoft

Ben Truelove 

Microsoft

Blaine Tsugawa 

OFCM, NOAA

Jonathan Upchurch, Ph.D., P.E. 

University of Massachusetts—Amherst

Dave Wheatley 

Motorola Laboratories 

Peter Wolff 

DaimlerChrysler Research and Technology 

Steve Wreggit 

DaimlerChrysler Research and Technology 
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CHAPTER 15: RELEVANT U.S. DEPARTMENT OF TRANSPORTATION, SOCIETY 

OF AUTOMOTIVE ENGINEERS, AND INTERNATIONAL ORGANIZATION FOR 

STANDARDIZATION DOCUMENTS 

Environmental and facility safety signs ANSI Z535.2 .............................................................15-3 

Criteria for safety symbols ANSI Z535.3.................................................................................15-4 

Product safety signs and labels ANSI Z535.4 ..........................................................................15-5 

Specification for symbols for controls, indicators and tell-tales for road vehicles 

BS AU 143f....................................................................................................................15-6 

Definitions, abbreviations, and symbols ETSI EG 201 013 .....................................................15-7 

Framework for the development, evaluation, and selection of graphical symbols 

ETSI EG 201 379...........................................................................................................15-8 

The Multiple Index Approach (MIA) for the evaluation of pictograms 

ETSI ETR 070................................................................................................................15-9 

Results of an evaluation study of pictograms for point-to-point videotelephony 

ETSI ETR 113..............................................................................................................15-10

Pictograms for point-to-point videotelephony ETSI ETS 300 375 ........................................15-11 

Federal Motor Vehicle Safety Standards: Controls and displays—Passenger cars, 

multipurpose passenger vehicles, trucks, and buses FMVSS 101..............................15-12 

Road vehicles—Symbols for controls, indicators, and tell-tales ISO 2575............................15-13 

Safety colours and safety signs ISO 3864...............................................................................15-14 

Public information symbols ISO 7001....................................................................................15-15 

Development and principles for application of public information ISO 7239 .......................15-16 

Basic principles for graphical symbols for use on equipment. Part 1: Creation of 

graphical symbols ISO/IEC 80461-1..........................................................................15-17 

Basic principles for graphical symbols for use on equipment. Part 2: Form and use 

of arrows ISO/IEC 80461-2........................................................................................15-18 

Graphical symbols—Test methods for judged comprehensibility and 

for comprehension ISO 9186......................................................................................15-19 

 15-1
Information technology—User system interfaces—Icon symbols and functions. 

Part 2: Object icons ISO/IEC 11581-2.......................................................................15-20 

Information technology—User system interfaces—Icon symbols and functions. 

Part 6: Action icons ISO/IEC 11581-6 ......................................................................15-21 

Road vehicles: Ergonomic aspects of transport information and control systems— 

Specifications and compliance procedures for in-vehicle visual presentation 

ISO/DIS 15008.............................................................................................................15-22

Procedures for designing, evaluating, and selecting symbols, pictograms, and icons 

ITU-T F.910.................................................................................................................15-23 

Manual on Uniform Traffic Control Devices (MUTCD) .......................................................15-24 

Standardization agreement: Symbols in designating function of controls in 

transport vehicles NATO STANAG 4050..................................................................15-25 

Instrumentation SAA ADR 18/02...........................................................................................15-26 

Development, testing, and implementation of information and safety symbols and 

symbolic signs SAA AS 2342 ....................................................................................15-27 

Public information symbol signs—Consolidated index SAA AS 2899.0 ..............................15-28 

Public information symbol signs—General information signs SAA AS 2899.1....................15-29 

Human interface design methodology for integrated display symbology 

SAE ARP 4155-A........................................................................................................15-30 

Emergency placarding—Internal and external SAE ARP 577-C...........................................15-31 

Symbols for motor vehicle controls, indicators, and tell-tales, standard SAE J1048.............15-32 

Safety signs SAE J115............................................................................................................15-33 

Graphical symbols for operator controls and displays on off-road self-propelled 

work machines SAE J1362 .........................................................................................15-34 

Photometric guidelines for instrument panel displays that accommodate 

older drivers SAE J2217 .............................................................................................15-35 

Road vehicles: Symbols for controls, indicators, and tell-tales SAE J2402..........................15-36 

 15-2
Reference No. 

ANSI Z535.2

Report Date

June 3, 1998

Title 

Environmental and facility safety signs

Number of Pages 

22 

Author(s) 

ANSI Accredited Standards Committee Z535 on Safety Signs 

and Colors, Subcommittee Z535-2: Environmental and Facility 

Safety Signs 

Organization

American National Standards Institute (ANSI) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Washington, DC Headquarters 

1819 L Street, NW, 6th Floor

Washington, DC 20036

www.ansi.org

General Topic

Major Headings

Summary

Specifications for safety and warning signs and placards 

 Safety sign colors and formats 

 Sign design/layout

 Sign color specifications

 Symbols/pictorials

 Letter style and size 

 Sign finish 

 Sign placement 

 Illumination

This standard establishes requirements for a uniform visual system of identification 

related to potential hazards in the environment. It provides for the design, 

application, and use of signs and placards employing this visual alerting system. 

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 15-3
Reference No. 

ANSI Z535.3

Report Date

April 9, 1998

Title 

Criteria for safety symbols 

Number of Pages 

48 

Author(s) 

ANSI Z535 Committee on Safety Signs and Colors, 

Subcommittee Z535-3 on Criteria for Safety Symbols 

Organization

American National Standards Institute (ANSI) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Washington, DC Headquarters 

1819 L Street, NW, 6th Floor

Washington, DC 20036

www.ansi.org

General Topic

Major Headings

Summary

This standard provides guidance in selecting symbols to alert people to hazards and to

provide general safety messages. 

Design specifications, development, and evaluation of symbols for use in safety and 

warning signs.

 Symbol types and colors 

 Graphic design considerations

 Symbol selection criteria 

 Symbol examples 

 References 

 Principles and guidelines for graphical design of hazard symbols 

 General procedures for evaluating candidate symbols 

 Symbol examples not meeting comprehension testing criteria for acceptance

This standard provides general criteria for the design, evaluation, and use of safety 

symbols to identify and warn against specific hazards, and to provide information to

avoid personal injury. 

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 15-4
Reference No. 

ANSI Z535.4

Report Date

April 28, 1998 

Title 

Product safety signs and labels 

Number of Pages 

18 

Author(s) 

ANSI Z535 Committee on Safety Signs and Colors, 

Subcommittee Z535-4 on Product Safety Signs and Labels

Organization

American National Standards Institute (ANSI) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Washington, DC Headquarters 

1819 L Street, NW, 6th Floor

Washington, DC 20036

www.ansi.org

General Topic

Major Headings

Summary

This standard provides guidance for manufacturers, employers, distributors, and 

others who have a desire to alert persons to potential personal injury hazard inherent

in products. 

 Sign classifications 

 Sign or label format

 Safety sign and label colors 

 Letter style and size 

 Sign and label placement 

 Expected life and maintenance 

 Symbols/pictorials

 References 

 Guidelines for increasing recognition of safety label components 

 Principles and guidelines for the design of product safety signs and labels

This standard sets forth performance requirements for the design, application, use,

and placement of safety signs and labels intended to identify potential hazards for 

people using, operating, servicing, or in proximity to, a wide variety of products. A 

product safety sign or label should alert people to a specific hazard, the degree of 

level of hazard seriousness, the probable consequence of involvement with the

hazard, and how the hazard can be avoided. 

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 15-5
Reference No. 

BS AU 143f

Report Date

July 1999 

Title 

Specification for symbols for controls, indicators and tell-tales 

for road vehicles 

Number of Pages 

20 

Author(s) 

Technical Committee AUE/12, Safety related to occupants

Organization

British Standard Institute (BSI) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

389 Chiswick High Road 

London W4 4AL 

United Kingdom 

www.bsi.org.uk

General Topic

Major Headings

Summary

Standard symbols for vehicle instrumentation 

 General 

 Color 

 Designation and illustration of symbols 

This international standard establishes the symbols (conventional signs) for use on

controls, indicators, and tell-tales of a road vehicle to ensure identification and

facilitate use. 

It also indicates the colors of possible optical tell-tales that inform the driver of either 

correct operation or malfunctioning of the related devices. 

Note: Same as ISO 2575

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 15-6
Reference No. 

ETSI EG 201 013 

Report Date

April 1997

Title 

Definitions, abbreviations, and symbols 

Number of Pages 

15 

Author(s) 

Human Factors Technical Committee of the ETSI 

Organization

European Telecommunications Standards Institute 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

F-06921 Sophia Antipolis Cedex

France 

www.etsi.org

General Topic

Major Headings

Summary

Provides the preferred definitions of human factors related terms as well as keywords, 

abbreviations, and symbols in telecommunication human factors documents. 

 Symbols 

This ETSI Guide (EG) presents a list of the definitions, abbreviations, and symbols 

used in the documents prepared by the ETSI Technical Committee for Human Factors 

(TC-HF).

The purpose of this EG is to give guidance to TC-HF rapporteurs in the preparation of

their documents, and to enhance the usability of these documents through the use of

consistent terminology. The definitions, abbreviations and symbols given are not

intended to be exclusive. Other definitions, abbreviations, and symbols different

from those given here may be found in some TC-HF documents. However, the 

definitions in this technical report are generally to be preferred.

The intended users of this EG include: 

 ETSI TC-HF 

 Other ETSI TCs and STCs

 User groups 

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 15-7
Reference No. 

ETSI EG 201 379 

Report Date

December 1998 

Title 

Framework for the development, evaluation, and selection of 

graphical symbols 

Number of Pages 

16 

Author(s) 

Human Factors Technical Committee of the ETSI 

Organization

European Telecommunications Standards Institute 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

F-06921 Sophia Antipolis Cedex

France 

www.etsi.org

General Topic

Major Headings

Summary

Use and selection of graphical symbols 

 Appropriate use of graphical symbols 

 Selection of graphical symbols 

 Development of new graphical symbols 

 Evaluation 

This document provides a framework for the development, evaluation, and selection 

of graphical symbols for application with telecommunications on terminals (on 

telecommunications equipment and for telecommunications functionality of humancomputer interfaces, e.g. on keyboards and screens), within telecommunications 

services (e.g., to denote the availability of and access to a telecommunications 

service), as well as in printed materials (e.g., user guides and directories).

The document is applicable to relevant factors including:

 Appropriate use of graphical symbols 

 Development of new graphical symbols for specific areas 

 Evaluation of graphical symbols using the ETSI Multiple Index Approach (MIA) 

Symbols for graphical programming or description languages are not included in the 

scope of this document. 

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 15-8
Reference No. 

ETSI ETR 070 

Report Date

June 1993

Title 

The Multiple Index Approach (MIA) for the evaluation of

pictograms 

Number of Pages 

23 

Author(s) 

Human Factors Technical Committee of the ETSI 

Organization

European Telecommunications Standards Institute 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

F-06921 Sophia Antipolis Cedex

France 

www.etsi.org

General Topic

Major Headings

Summary

Describes the Multiple Index Approach (MIA) methodology used for the evaluation

and adoption of new pictograms. 

 Introduction

 Evaluating pictograms by multiple indices 

 Structure of the MIA questionnaire 

 Analysis 

 Making a decision based on the results

 The special case of testing one pictogram set only 

 Conclusion

This ETR describes the MIA method for evaluating pictograms. This method has

been developed, tested, and employed in the context of an ETSI (TC Human Factors)

study on pictograms for basic videophone functions and the examples given are taken 

from this study. This method has been found to be suitable as a general testing 

method for pictograms from all areas. The method described here takes the form of a 

questionnaire test, but it can be administered by other means as well (e.g., on a 

personal computer). 

The main purpose of a pictogram evaluation study using MIA is to collect data and 

identify the best suited pictograms from a number of proposed pictograms. 

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 15-9
Reference No. 

ETSI ETR 113 

Report Date

October 1993 

Title 

Results of an evaluation study of pictograms for point-to-point

videotelephony

Number of Pages 

57 

Author(s) 

Human Factors Technical Committee of the ETSI 

Organization

European Telecommunications Standards Institute 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

F-06921 Sophia Antipolis Cedex

France 

www.etsi.org

General Topic

Major Headings

Summary

Detailed report of an empirical evaluation study of pictograms for point-to-point 

videotelephony functions. 

 General 

 The ETSI study of pictograms for point-to-point videophone functions

 Method

 Results 

 Discussion of the results 

 The recommendation of pictograms for point-to-point videotelephony

 The post-test 

This ETSI Technical Report (ETR) gives the results of an evaluation study of

pictograms for basic videotelephony functions. 

Seven pictogram sets, each containing candidate pictograms for the seven basic 

videophone functions, were empirically evaluated with the aim of identifying the 

most suitable pictogram set. Data for this study were collected in eight European 

countries from more than 650 respondents. The results of the study lead to the 

recommendation of a combined set of pictograms. 

The Multiple Index Approach to the evaluation of pictograms is described in detail in 

ETR 070 (see page 14-9). The seven recommended pictograms are the content of

ETS 300 375 (see page 14-11). 

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 15-10
Reference No. 

ETSI ETS 300 375 

Report Date

November 1994

Title 

Pictograms for point-to-point videotelephony

Number of Pages 

18 

Author(s) 

Human Factors Technical Committee of the ETSI 

Organization

European Telecommunications Standards Institute 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

F-06921 Sophia Antipolis Cedex

France 

www.etsi.org

General Topic

Major Headings

Summary

Specifications and standardized pictograms to ease the use of point-to-point 

videotelephony. 

 Scope 

 Normative references 

 Definitions 

 Pictograms for point-to-point telephony

 ETSI pictograms for the eight videophone functions 

This ETS defines pictograms for representing eight point-to-point videotelephony

functions. 

1) Videophone / telephone 

2) Videophone / camera on/off

3) Videophone / microphone on/off 

4) Videophone / selfview on/off

5) Videophone / still picture on/off 

6) Videophone / document camera on/off 

7) Videophone / handsfree on/off 

8) Videophone / loudspeaker on/off

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 15-11
Reference No. 

FMVSS 101

Report Date

October 1, 2000

Title 

Federal Motor Vehicle Safety Standards: Controls and displays 

—Passenger cars, multipurpose passenger vehicles, trucks and 

buses 

Number of Pages 

8 

Author(s) 

Organization

National Highway Traffic Safety Administration 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Office of Vehicle Safety Compliance 

400 7th Street SW

Room 6111, Mail Code: NSA-30

Washington, DC 20590

General Topic

Major Headings

Summary

Specifications for the visibility of vehicle instrumentation

 Definitions 

 Requirements 

 Location

 Identification

 Illumination

 Conditions

This standard specifies requirements for the location, identification, and illumination

of motor vehicle controls and displays. 

The purpose of this standard is to ensure the accessibility and visibility of motor 

vehicle controls and displays and to facilitate their selection under daylight and

nighttime conditions, in order to reduce the safety hazards caused by the diversion of

the driver’s attention from the driving task and by mistakes in selecting controls. 

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Price 

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 15-12
Reference No. 

ISO 2575 

Report Date

March 15, 2000

Title 

Road vehicles—Symbols for controls, indicators, and tell-tales 

Number of Pages 

41 

Author(s) 

Technical Committee ISO/TC 22: Road vehicles, SC 13:

Ergonomics applicable to road vehicles 

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Standard symbols for vehicle instrumentation 

 General 

 Color 

 Symbols and descriptions 

This international standard establishes symbols (i.e., conventional signs) for use on

controls, indicators, and tell-tales of a road vehicle to ensure identification and

facilitate use. 

It also indicates the colors of possible optical tell-tales that inform the driver of either 

correct operation or malfunctioning of the related devices. 

Note: Also published under

 BS AU 143f (British Standards Institute) 

 SAE 2042 (Society of Automotive Engineers)

Report date reflects most recent full draft 

 Amendment 1 published March 22, 2001

 Amendment 4 published August 2, 2001

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 15-13
Reference No. 

ISO 3864 

Report Date

March 1, 1984 

Title 

Safety colours and safety signs

Number of Pages 

14 

Author(s) 

Technical Committee ISO/TC 80 

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Use of color in sign and symbol design

 Safety colors and contrast colors 

 Geometric form and meaning of safety signs

 Design of graphic symbols 

 Layout of safety signs 

 Supplementary signs 

 Colorimetric and photometric properties of materials 

 Examples of safety signs 

This international standard prescribes safety colors and safety signs for the purposes 

of preventing accidents and health hazards and meeting emergencies. 

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 15-14
Reference No. 

ISO 7001 

Report Date

February 1990 

Title 

Public information symbols 

Number of Pages 

112 

Author(s) 

Technical Committee ISO/TC 145: Graphical symbols

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Catalog of public information symbols 

 Numerical index and summary of public information symbols 

 Compilation of single sheets 

This international standard specifies the image content of graphical symbols used for 

the public information. The field of application specified for each graphical symbol 

is indicative of the way it is intended that the symbols should be used; their 

application may be extended into other fields where this is considered appropriate. 

Report date reflects most recent full draft 

 Amendment 1 published June 1993

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 15-15
Reference No. 

ISO 7239 

Report Date

December 15, 1984 

Title 

Development and principles for application of public 

information

Number of Pages 

18 

Author(s) 

Technical Committee ISO/TC 145/SC 1: Public information 

symbols

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Procedures for the development or adoption of public information symbols 

 Development of public information symbols 

 Visual design criteria 

 Sign layout

This technical report recommends procedures to be followed and sets forth the 

essential technical criteria that should be taken into account when developing or

considering the use of graphical symbols as a means of visual pictorial

communication. 

The field of application is mainly in public areas, but the recommendations of this 

technical report concerning visual design criteria can equally be applicable to

perception problems in other areas where graphical symbols are used as the means of 

communication. 

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 15-16
Reference No. 

ISO/IEC 80461-1

Report Date

June 2001

Title 

Basic principles for graphical symbols for use on equipment.

Part 1: Creation of graphical symbols 

Number of Pages 

31 

Author(s) 

IEC subcommittee 3C: Graphical symbols for use on 

equipment, of IEC technical committee 3: Information

structures, documentation and graphical symbols

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Creation of graphical symbols 

 Symbol meaning 

 Combination of graphical symbols 

 Creation principles 

 Basic pattern

 Application of symbol originals 

 Creation procedure 

 Designation systems 

This multipart standard addresses the basic rules for creating graphical symbols for 

use on equipment, including line widths, form and use of arrows, negation elements, 

and use of the basic pattern that serves as a guideline for drawing equipment symbols. 

These design principles are required to be used for all graphical symbols on

equipment; the standardized graphical symbols for which are found in ISO 7000 and

IEC 60417. 

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 15-17
Reference No. 

ISO/IEC 80461-2

Report Date

July 15, 2001

Title 

Basic principles for graphical symbols for use on equipment.

Part 2: Form and use of arrows

Number of Pages 

7 

Author(s) 

Technical Committee ISO/TC 145, Graphical symbols, and

Technical Committee IEC/TC 3, Documentation and graphical

symbols

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Use of arrow in graphical symbols 

 General principles 

 Definitions of arrow forms and specific meaning 

 Movement

 Speed and acceleration 

 Special meaning of function and force 

 Dimensions 

This international standard addresses the basic rules for creating graphical symbols 

for use on equipment, including line widths, form and use of arrows, negation 

elements, and use of the basic pattern that serves as a guideline for drawing 

equipment symbols. These design principles are required to be used for all graphical

symbols on equipment; the standardized graphical symbols for which are found in

ISO 7000 and IEC 60417. 

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 15-18
Reference No. 

ISO 9186 

Report Date

April 1, 2001

Title 

Graphical symbols—Test methods for judged comprehensibility 

and for comprehension 

Number of Pages 

36 

Author(s) 

Technical Committee ISO/TC 145: Graphical symbols, SC 1:

Public information symbols

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Methods to assess comprehensibility of graphical symbols 

 Terms and definitions 

 Procedures

 Tests using printed presentation 

 Tests using computer screen presentation 

 Accepting a variant as a standard graphical symbol 

 Collection of information

 Comprehensibility judgments test 

 Comprehension test

 Approved testing 

This international standard specifies: 

 The procedure to be used in gathering the information needed to request 

standardization of graphical symbols. 

 The method to be used in testing which variant of a graphical symbol is judged

the most comprehensible. 

 The method to be used in testing the extent to which a variant of a graphical 

symbol communicates its intended message. 

The purpose of this international standard is to ensure that graphical symbols, and

signs using graphical symbols, are readily understood. It in no way ensures 

compliance with prohibitions or warnings using graphical symbols or symbol signs 

designed in accordance with this international standard. 

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 15-19
Reference No. 

ISO/IEC 11581-2

Report Date

April 1, 2000

Title 

Information technology—User system interfaces—Icon symbols 

and functions. Part 2: Object icons 

Number of Pages 

31 

Author(s) 

Joint Technical Committee ISO/IEC JTC 1: Information 

technology, SC 35: User interfaces

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Design of computer icons that represent objects 

 Conceptual construction of object icons 

 Object icon requirements and recommendations 

 Icon specifications 

 Minimum information to be given when submitting an icon

ISO/IEC 11581-2 applies to icons that are shown on a screen, that users can

manipulate and interact with, and that represent data, or computer system functions. 

This part of ISO/IEC 11581 addresses only object icons. “Objects icons” is a term

used in ISO/IEC 11581-2 to describe icons that represent functions by association 

with an object and that can be moved and opened. Other types of icons, listed in the 

foreword, are covered in other parts of the standard. 

Annex A describes the information to be given when submitting new object icons for

inclusion in this part of ISO/IEC 11581. 

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 15-20
Reference No. 

ISO/IEC 11581-6

Report Date

February 1, 1999 

Title 

Information technology—User system interfaces—Icon 

symbols and functions. Part 6: Action icons 

Number of Pages 

20 

Author(s) 

Joint Technical Committee ISO/IEC JTC 1: Information 

technology

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Design of computer icons representing action 

 Conceptual construction of action icons 

 Action icon requirements and recommendations 

 Action icon specifications

ISO/IEC 11581-6 applies to icons that are shown on a screen, that users can

manipulate and interact with, and that represent data or computer system functions. 

This part of ISO/IEC 11581 addresses only action icons. Action icons represent 

actions by association with objects that prompt the user to recall the intended

actions. This part of ISO/IEC 11581 describes user interaction with and appearance 

of action icons on the screen. Other types of icons listed in the foreword, are 

covered in other parts of the standard. 

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 15-21
Reference No. 

ISO/DIS 15008

Report Date

November 12, 2001

Title 

Road vehicles: Ergonomic aspects of transport information and 

control systems—Specifications and compliance procedures for 

in-vehicle visual presentation 

Number of Pages 

26 

Author(s) 

Technical Committee ISO/TC 22, Road vehicles, 

Subcommittee SC 13, Ergonomics

Organization

International Organization for Standardization (ISO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Case postale 

CH-1211 Geneva 20 

Switzerland

www.iso.ch

General Topic

Major Headings

Summary

Visual characteristics of dynamic visual displays 

 Specifications and measurement methods 

 Design viewing position and illumination range

 Luminance contrast 

 Color 

 Alphanumerical character dimensions 

 Pixel matrixes character format 

 Reflections and glare 

 Characteristics of presentation

This international standard gives minimum specifications for the image quality of

displays that contain dynamic (changeable) visual information for road vehicle 

drivers from an on-board Transport Information and Control System (TICS) used

while the vehicle is in motion, so that those displays are legible. 

The specifications described in this standard are intended to be independent of

display technologies. They address mainly the perceptual components and some

basic cognitive components of the visual information (e.g., character legibility and 

color recognition). Other factors that affect performance and comfort (such as

coding, format, and dialogue characteristics) are covered in other standards.

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 15-22
Reference No. 

ITU-T F.910 

Report Date

February 1995 

Title 

Procedures for designing, evaluating, and selecting symbols, 

pictograms, and icons 

Number of Pages 

7 

Author(s) 

ITU-T Study Group 1: Telecommunication Standardization 

Sector of ITU 

Organization

International Telecommunication Union (ITU) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

Place des Nations 

CH-1211 Geneva 20 

Switzerland

www.itu.int

General Topic

Major Headings

Summary

User-centered design and evaluation process for pictograms

 Methodology

 General parameters of experiments 

 Other considerations 

Various national, regional, and international standards organizations are responsible 

for the design, evaluation, and standardization of symbols, pictograms, and icons. To

coordinate the work of these standards organizations, and to optimize the designs, it is

desirable to follow a well-defined methodology. This recommendation describes a 

framework for a common methodology to be used by the ITU-T. To the extent that

other standards organizations can work within this framework, the development of

important designs should progress more rapidly. A uniform methodology will 

minimize duplication of effort and will maximize the relevance of collected data. 

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 15-23
Reference No. 

MUTCD

Report Date

June 2001

Title 

Manual on Uniform Traffic Control Devices (MUTCD) 

Number of Pages Author(s) 

National Committee on Uniform Traffic Control Devices 

Organization

U.S. Dept. of Transportation, Federal Highway Administration 

(FHWA)

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

400 7th Street, SW

Washington, DC 20590

General Topic

Major Headings

Summary

Standard practices for traffic control and devices 

 General provisions 

 Guide signs 

 Markings

 Highway traffic signals 

 Low-volume rural roads 

 Work zones 

 Traffic controls for school areas 

 Traffic controls for highway/rail grade crossings 

 Traffic controls for bicycle facilities 

 Traffic controls for highway/light rail transit grade crossings 

Traffic control devices are defined as all signs, signals, markings, and other devices 

used to regulate, warn, or guide traffic and placed on, over, or adjacent to a street, 

highway, pedestrian facility, or bikeway by authority of a public agency having

jurisdiction.

The material described in this edition of the MUTCD provides the transportation

professional with the information needed to make appropriate decisions regarding the 

use of traffic control devices on streets and highways. The material in this edition is 

organized to better differentiate between standards that must be satisfied for the 

particular circumstances of a situation, guidances that should be followed for the 

particular circumstances of a situation, and options that may be applicable for the 

particular circumstances of a situation. 

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 15-24
Reference No. 

NATO STANAG 4050 

Report Date

May 13, 1969

Title 

Standardization agreement: Symbols in designating function of

controls in transport vehicles 

Number of Pages 

14 

Author(s) 

Organization

North Atlantic Treaty Organization (NATO) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

NATO Headquarters 

Blvd Leopold III 

1110 Brussels, Belgium

natodoc@hq.nato.int

General Topic

Major Headings

Summary

Standardization of transport vehicle control instrumentation 

 Contours for functional categories 

 System of symbols designed to replace or supplement the text of instruction 

plates and forms for transport vehicles 

The object of this agreement is to standardize symbols to replace lettering on controls 

in transport vehicles for the NATO Armed Forces. 

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 15-25
Reference No. 

SAA ADR 18/02 

Report Date

December 1998 

Title 

Instrumentation 

Number of Pages 

5 

Author(s) 

Organization

Department of Transport and Regional Services: Land

Transport 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

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GPO Box 594 

Canberra ACT 2601

Australia 

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General Topic

Major Headings

Summary

Specifications for location and visibility of passenger vehicle visual indicators 

 Visual indicators 

 Location of visual indicators 

 Visibility of visual indicators 

 Speedometers and odometers

The function of this national standard is to specify requirements for the provision and 

location of certain “visual indicators.” It also specifies requirements for

speedometers and odometers. 

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 15-26
Reference No. 

SAA AS 2342 

Report Date

October 12, 1992 

Title 

Development, testing, and implementation of information and 

safety symbols and symbolic signs 

Number of Pages 

40 

Author(s) 

Committee MS/3, Public Information Symbols

Organization

Standards Association of Australia (SAA) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

1 The Crescent

Homebush, NSW 2140

Australia

General Topic

Major Headings

Summary

Development, evaluation, and adoption of symbol signs 

 Determination of need for a symbol and establishment of design criteria 

 Selection and testing of graphic symbols and symbolic signs 

 Principles for the design of graphic symbols 

 Principles for the design of signs incorporating symbols 

 Siting and maintenance 

 Establishment of need for a graphic symbol or symbolic sign 

 Method of collection and appropriateness assessment of symbol and symbol sign

variants for comprehension and related testing

 Comprehension and recall tests 

 Photometric and colorimetric properties of sign materials 

 Sources of potential test symbols 

This standard specifies principles and procedures for determining the need, selection,

testing, and design of graphic symbols for: 

a. Equipment or parts of equipment to instruct or advise people handling the 

equipment as to its use and operation; 

b. Locations where people may work, assemble, or move, to give them

information or instructions, such as prohibitions, warnings, rules, limits, or

directional guidance; or 

c. Pictorial representations on maps, plans, drawings, illustrations, and similar 

documents. 

It also specifies principles and procedures for the design and use of information and 

safety signs using these symbols.

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 15-27
Reference No. 

SAA AS 2899.0

Report Date

September 5, 1986

Title 

Public information symbol signs—Consolidated index 

Number of Pages 

13 

Author(s) 

Committee MS/3, Public Information Symbols

Organization

Standards Association of Australia (SAA) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

1 The Crescent

Homebush, NSW 2140

Australia

General Topic

Major Headings

Summary

Numerical index for standardized information signs 

 Numerical Index 

This standard lists the referents for standard public information symbol signs and

gives the function and fields of application for each sign. It also defines terms used in

this standard and on the single sheets in: 

AS 2899.1 General Information Signs 

AS 2899.2 Water Safety Signs 

AS 2899.3 Hospital Signs 

AS 2899.4 Signs for the Working Environment 

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 15-28
Reference No. 

SAA AS 2899.1

Report Date

September 5, 1986

Title 

Public information symbol signs—General information signs 

Number of Pages 

53 

Author(s) 

Committee MS/3, Public Information Symbols 

Organization

Standards Association of Australia (SAA) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

1 The Crescent

Homebush, NSW 2140

Australia

General Topic

Major Headings

Summary

Single sheets for general information signs 

 General information signs 

This standard includes black-and-white single sheets for general information signs. 

Note: Many symbols are the same as those described in ISO 7001. 

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 15-29
Reference No. 

SAE ARP 4155-A

Report Date

October 1997 

Title 

Human interface design methodology for integrated display 

symbology 

Number of Pages 

19 

Author(s) 

SAE Subcommittee G-10I, Symbology for Electronic Displays

of the SAE Committee G-10, Aerospace Behavioral 

Engineering Technology

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Design methodology for development of symbology

 Background

 Design methodology 

This standard describes a recommended design approach that emphasizes the 

fundamental relationship between symbols, the information they encode, the context

within which the symbols are displayed, and the tasks being supported. While this 

document is aimed at aircraft displays involving dynamic control or monitoring tasks,

the methodology is applicable to a wide range of symbology development situations. 

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 15-30
Reference No. 

SAE ARP 577-C 

Report Date

March 16, 1993

Title 

Emergency placarding—Internal and external

Number of Pages 

7 

Author(s) 

SAE Committee S-9, Cabin Safety Provisions

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Specifications for the design of aircraft emergency placards 

 Information presentation 

 Written instructions

 Pictorial instructions

 Minimum-sized pictures and words 

 Color of placard and background 

 Location

 Warnings 

This SAE Aerospace Recommended Practice (ARP) provides criteria for the 

development and standardization of placards containing easily understood signs, 

symbols, and/or instructions for locating and operating exits and emergency 

equipment that might be used or operated by cabin occupants and rescue personnel

under emergency conditions. In addition, this ARP gives guidance in the selection

and development of warning labels. The placards are intended to be seen and

understood by occupants inside and, in the case of external exit placards, by persons 

outside the airplane. 

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 15-31
Reference No. 

SAE J1048 

Report Date

March 1980

Title 

Symbols for motor vehicle controls, indicators and tell-tales, 

standard 

Number of Pages 

16 

Author(s) 

SAE Human Factors Engineering Committee 

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Standardized symbols for vehicle instrumentation 

 Designation and illustration of symbols 

This standard specifies the symbols, that is, conventional signs, with which certain 

controls, indicators and tell-tales of a road vehicle are to be provided to ensure their 

identification and facilitate their utilization.

It also indicates the colors of possible optical tell-tales, which warn the driver of the 

operation or malfunctioning of the devices and equipment connected to the 

corresponding controls. 

This standard is applicable to those controls that are fitted on the instrument panel, or 

in the immediate vicinity of the driver. 

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 15-32
Reference No. 

SAE J115

Report Date

February 1995 

Title 

Safety signs 

Number of Pages 

10 

Author(s) 

SAE Human Factors Technical Committee SC2 – Machine

Displays and Symbols

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Guidelines for signage symbols 

 Sign format 

 Letter style and size 

 Sign placement 

 Expected life and maintenance 

 Pictorials 

 Guidelines for creating pictorials 

This SAE standard establishes signal words, color combinations, letter sizes, and 

durability requirements for permanently and temporarily affixed safety signs for offroad, self-propelled work machine categories of construction, general purpose 

industrial, forestry, agricultural tractors, and specialized mining machinery as defined 

in SAE J1116. This document is suitable for application to tools, machines, and 

machinery used in the specified categories. 

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 15-33
Reference No. 

SAE J1362 

Report Date

July 1997 

Title 

Graphical symbols for operator controls and displays on offroad self-propelled work machines 

Number of Pages 

81 

Author(s) 

SAE Human Factors Technical Committee SC2: Machine 

Displays and Symbols

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Standardized symbols for off-road machinery

 Symbol

 General 

 Color 

 Development of new symbols 

 Standardized symbology

 Guidelines for development and evaluation of graphical symbols 

SAE J1362 presents graphical symbols for use on operator controls and other displays

on construction, general-purpose industrial, agricultural, forestry, and specialized 

mining categories of off-road self-propelled work machines, as defined in SAE 

J1116. Symbols for agricultural equipment other than the basic agricultural tractor 

(for example, combine harvesters, cotton harvesters, forage harvesters, balers, and 

sprayers) are covered by ASAE S304 and are therefore excluded from the scope of

SAE J1362. 

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 15-34
Reference No. 

SAE J2217 

Report Date

October 1991 

Title 

Photometric guidelines for instrument panel displays that

accommodate older drivers 

Number of Pages 

6 

Author(s) 

SAE Mature Driver Standards Committee 

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Provides introductory information that should be considered when setting

photometric guidelines for instrument panel displays that are designed to

accommodate the older driver. 

 Luminance contrast 

 Color usage 

 Color preference 

 Brightness preference 

 Gloss 

Physical parameters that influence the legibility of an instrument panel display 

include: letter/graphic size; the luminance and color difference between graphics and 

background; the observer’s luminance adaptation level; and the level of the glare 

present. Several aspects of visual functioning deteriorate as part of the normal aging 

process. These include: a reduction in luminance and color-contrast sensitivity; an

increase in sensitivity to glare; a reduction in visual accommodation capacity; and a 

reduction in the sensitivity to light. This SAE information report provides 

introductory information that should be considered when setting photometric 

guidelines for instrument panel displays that are designed to accommodate the older 

driver. 

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 15-35
Reference No. 

SAE J2402 

Report Date

June 1997

Title 

Road vehicles: Symbols for controls, indicators, and tell-tales 

Number of Pages 

18 

Author(s) 

SAE Controls and Displays Standards Committee 

Organization

Society of Automotive Engineers, Inc. (SAE) 

Type of Report 

 Technical Report

 Guidelines

 Standard 

 International Standard

Organization Address 

SAE World Headquarters 

400 Commonwealth Drive 

Warrendale, PA 15096-0001 

www.sae.org

General Topic

Major Headings

Summary

Standard symbols for vehicle instrumentation 

 General 

 Color 

 Designation and illustration of symbols 

This SAE standard establishes the symbols (i.e., conventional signs) for use of

controls, indicators, and tell-tales of a road vehicle to ensure identification and

facilitate use. It also indicates the colors of possible optical tell-tales that inform the 

driver of either correct operation or malfunctioning of the related devices. 

Note: Same as ISO 2575. 

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 15-36
CHAPTER 16: INDEX

Bold indicates glossary definition. 

A

Advanced Traveler Information System (ATIS), 2-7, 12-1

Appropriateness Ranking Test, 7-6, 12-1

Audio signals, ratings of, 6-4 

Auditory 

icons, 6-1 

icons, design of, 6-12 

information, 6-2, 

messages, examples of, 6-14 

presentation of in-vehicle information, 6-1 

signal, 6-4 

signals, perceived urgency of, 6-16 

Augmented signage information icons, 8-3 

Augmenting 

icons with auditory information, 6-2 

Automated cruise control devices icons, 8-5 

Automatic Speech Recognition (ASR), 12-1

Automatic Speech Recognition systems, design guidelines for, 6-18 

B

C

Cathode Ray Tube (CRT), 12-2

Collection, Icon, 8-1 

Collision avoidance information icons, 8-5 

Commercial vehicle operations (CVO), 12-2

Commercial vehicle operations (CVO) information icons, 8-10 

Color 

effects on icon legibility, 3-10 

enhancing icon interpretation with, 5-12 

Comprehension/Recognition Test, 7-8 

Contrast 

within an icon, 3-4 

equation for determining color, 3-10 

 16-1
Conveying 

effect of actions with icons, 5-6 

system status with icons, 5-10 

urgency with icons, 5-14 

D

Department of Transportation (DOT), 1-5, 12-2

Design guideline, 1-3 

Design of 

auditory icons, 6-12 

earcons, 6-10 

simple tones, 6-6 

speech messages, 6-14 

prohibition symbols, 4-10 

Design tool, 10-1 

sensory modality, 10-1 

steps for using, 10-2 

Detail, level of, 4-4 

Display modality, 10-3 

rules for determining, 10-3 

Driver-vehicle interface (DVI), 12-2

E

Earcons, 6-10 

design of, 6-10 

method for constructing, 6-10 

Effect of actions, conveying with icons, 5-6 

Equation 

effects of color on legibility, 11-2 

for appropriate luminance uniformity, 11-1 

for determining appropriate contrast, 11-1 

for determining appropriate size of components, 11-1 

for determining color contrast, 3-10 

perceived urgency of auditory signals, 11-2 

Equations, list of, 11-1 

Evaluation approaches, symbol, 7-12 

Evaluation procedures for in-vehicle icons, 7-2 

Examples 

Schematic, 5-6, 5-8, 5-12, 5-14, 

 16-2
F

Federal Highway Administration (FHWA), 12-3

Federal Motor Vehicle Safety Standards (FMVSS), 12-3

Field of view (FOV), 12-3

Flash rate, 4-8, 12-3

Font for symbols, 3-8 

foot lambert (fl), 12-3

Format, two-page, 1-1 

G

General navigation system information icons, 8-12 

Guideline, design, 1-3 

Guidelines, how to use, 1-1 

H

Head-Up Display (HUD), 12-3

Height of symbols, 3-6 

I

Icon Collection, 8-1 

Icon 

composition of an, 2-10 

comprehension, sequence of, 2-12 

contrast within an, 3-4 

design, 2-1 

design, perceptual principles of, 4-6 

interpretation, 5-1 

interpretation, enhancing with color, 5-12 

interpretation, enhancing with text labels, 5-2 

interpretation, enhancing with shape, 5-16 

legibility, 3-1 

luminance uniformity within an, 3-2 

recognition, 4-1 

Icon components, appropriate size of, 3-6 

 16-3
Icons 

auditory, 6-4 

auditory, design of, 6-10 

augmented signage information, 8-3 

augmenting with auditory information, 6-2 

automated cruise control devices, 8-5 

collision avoidance information, 8-5 

commercial vehicle operations (CV0) information, 8-10 

conveying effect of actions with, 5-6 

conveying system status with, 5-10 

conveying urgency with, 5-14 

evaluation procedures for in-vehicle, 7-2 

flashing, use of, 4-8 

general navigation systems information, 8-12 

identifying as part of a group, 5-8 

motorist services information, 8-12 

routing and navigation information, 8-34 

safety/warning information, 8-40 

ways to use, 2-6 

when to use, 2-4 

visual, 2-8 

Identifying icons 

as part of a group, 5-8 

Intelligent Transportation Systems (ITS), 12-4

Interface, driver-vehicle (DVI), 12-2

International Standards Organization (ISO), 1-1, 15-, 12-4

Interpretation of icons, 5-1 

enhancing with color, 5-12 

enhancing with shape, 5-16 

enhancing with text labels, 5-2 

In-vehicle icons 

development process for, 2-2 

In-Vehicle Information System (IVIS), 12-4

J

K

 16-4
L

Labels, text, 3-8, 5-2 

composition of, 5-4 

designing effective, 3-8 

Legibility 

icon, 3-1 

effects of color on, 3-10 

Level of 

detail, 4-4 

realism, 4-2 

Luminance uniformity of icons, 3-2 

M

Manual on Uniform Traffic Control Devices (MUTCD), 12-5

Matching Test, 7-10 

Messages, speech, 6-14 

design of, 6-14 

Motorist services information icons, 8-12 

N

O

Overview of procedures for evaluating in-vehicle icons, 7-2 

P

Perceptual principles of icon design, 4-6 

Perceived urgency of auditory signals, 6-16 

Production test, 7-4 

Prohibition symbols, design of, 4-10 

Q

 16-5
R

Rank order data, analysis of, 9-1 

Rating system, 1-3 

based on experimental data, 1-3 

based on expert judgment, 1-3 

Ratings 

audio signals, 6-4 

Realism, level of, 4-2 

Recognition, icon, 4-1 

Routing and navigation icons, 8-34 

S

Safety/warning information icons, 8-40 

Selection of 

colors for coding visual displays, 3-10, 5-12 

Sensory modality design tool, 10-1 

Sensory modality for presenting messages, 10-3 

Shape, enhancing icon interpretation with, 5-16 

Sign information, 8-3 

Signal-to-Noise Ratio (SNR), 12-6

Signals, audio, ratings of, 6-4 

Simple tones, 6-4 

design of, 6-6 

Society of Automotive Engineers (SAE), 1-5, 12-5

Spacing of symbols, 3-8, 5-8 

Speech messages, 6-4 

design of, 6-14 

Strokewidth-to-height ratio of symbols, 3-8, 12-7

Symbol 

color, 3-10 

contrast, 3-4 

contrast, equation for, 11-1 

evaluation approaches, 7-12 

font, 3-8 

 16-6
height, 3-6 

height, equation for, 11-1 

luminance uniformity, 3-2 

luminance uniformity, equation for, 11-1 

prohibition, 4-10 

spacing, 3-8, 5-8 

strokewidth-to-height ratio, 3-8 

width-to-height ratio, 3-8 

System, rating, 1-3 

System status, conveying with icons, 5-10 

T

Test 

Appropriateness Ranking, 7-6 

Comprehension/Recognition, 7-8 

Matching, 7-10 

Production, 7-4 

Text labels, 3-8, 5-2, 5-4 

composition of, 5-4 

designing effective, 3-8 

Tones, simple, 6-4 

design of, 6-6 

Transportation, Department of (DOT), 1-5, 12-2

Types of visual icons, 2-8 

U

Urgency, conveying with icons, 5-14 

Urgency, perceived, of auditory signals, 6-16 

V

Vacuum Fluorescent Display (VFD), 12-8

Visual angle, 3-6 

Visual Display Terminal (VDT), 12-8

Visual displays, selection of colors for coding, 3-10, 5-12 

Visual icons, types of, 2-8 

 16-7
W

Width-to-height ratio for symbols, 3-8, 12-7

X

Y

Z

 16-8