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Publication Number: FHWA-RD-03-065
Date: September 2004

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

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CHAPTER 12: GLOSSARY

ACC Automated Cruise Control
Appropriateness Ranking Test Refers to a test to screen the candidate symbols generated during the Production Test and to select the best for further testing.
ASR Automatic Speech Recognition
ATIS Advanced Traveler Information Systems.
Auditory signals Refers to simple tones, earcons, auditory icons, or speech messages.
Auditory icons These are familiar environmental sounds (iconic, metaphorical, and symbolic) that intuitively convey information about the object or action that they represent
Augmentation of icons with auditory information To make the message clearer or more salient, some type of auditory signal is included with an icon.
Automatic Speech Recognition (ASR) systems 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.
CAS Collision Avoidance System.
CIE Commission Internationale de l’Eclairage (International Lighting Commision).
Color coding 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 Composition of an icon refers to the parts that comprise an icon.
Comprehension/ Recognition Test 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.
Contrast The relationship between the luminance of a symbol and the luminance of the symbol’s background.
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.
Conveying system status with icons Refers to changing icon appearance to convey changes in the system state.
Conveying urgency with icons Urgency is conveyed by adjusting icon characteristics to reflect the appropriate level of urgency of the situation.
CRT Cathode Ray Tube.
CVO Commercial Vehicle Operations.
CVO-specific icons Icons that relate to commercial vehicle operations.
dB 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.
Development process for in-vehicle icons 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.
Display modality 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.
DOT Department of Transportation.
DVI Driver-Vehicle Interface.
Earcons Auditory signals that present information through musical tones that can be used in structured combinations to create auditory messages.
Evaluation of in-vehicle icons 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.
FHWA Federal Highway Administration.
Filtering sign information 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.
fL Foot lambert.
Flash rate The rate at which a signal alternates between an illuminated and a non-illuminated state.
Flashing icons Icons that flash on and off in a predetermined on/off cycle
FMVSS Federal Motor Vehicle Safety Standards.
Font segments 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.
FOV Field-of-View.
Grouping icons Grouping facilitates icon identification as a set of related messages or similar commands.
Guideline format The method used to present guidelines to system designers and developers.
HUD Head-Up Display.
Hz Hertz, a unit of frequency equal to one cycle per second.
Icon A visual representation or image used to symbolize an object, action, or concept.
Icon comprehension Refers to the perceptual and cognitive processes by which users interpret the meaning of an icon.
Icon interpretation enhanced with color Refers to the manner in which color can highlight information and enhance drivers’ interpretation of the icon.
Icon interpretation enhanced with shape 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.
Icon interpretation enhanced with text labels Refers to the manner in which the content of text labels can affect the comprehension and interpretation of an icon.
Icon legibility The reflection of the relationship between the driver, the icon, and the environment
Identification time task 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.
Information units Describe the amount of information presented in terms of key nouns and adjectives contained in a message.
ISO International Organization for Standardization.
ITS Intelligent Transportation Systems.
IVIS In-Vehicle Information System.
LCD Liquid crystal display.
Level of detail Refers to the amount of detail necessary for recognition of a symbol.
Level of realism Refers to the relationship between the portrayed object or concept and the graphic means used to represent that object or concept.
Luminance uniformity Refers to the consistency of luminance values across an icon.
Matching Test 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.
MUTCD Manual on Uniform Traffic Control Devices.
Perceived urgency of auditory signals Refers to the subjective impression of urgency that a signal gives to the person hearing it.
Perceptual principles of icon design Refers to design recommendations based solely on the visual characteristics of the icon without reference to its intended function or meaning.
Production test 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.
Prohibitive symbols Icons that present a specific action and communicate that the action should be avoided
Rating task Determines the degree to which a symbol suggests or communicates its designated name.
Reaction time task 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.
Relationship between in-vehicle icons and roadway signs 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.
R&D Research and Development.
SAE Society of Automotive Engineers.
Selection of colors for coding visual displays 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).
Semantic differential method 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.).
Sensory modality for presenting IVIS messages 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.
Simple tones Auditory signals that present information through the use of single or grouped frequencies presented simultaneously.
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.
SNR Signal-to-Noise Ratio.
Speech messages Auditory signals that present information through voice messages that add information beyond pure sound.
Symbol color 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
Symbol font Refers to the geometrical characteristics or style of symbology. Design goals for symbol font are to avoid extensive flourishes and embellishments of the symbols.
Symbol height 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.
Symbol spacing 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-symbol-height ratio).
Symbol strokewidth-to-height ratio Refers to the ratio of the symbol stroke thickness to symbol height.
Symbol versus text presentation of IVIS messages 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.
Symbol width-to-height ratio Refers to the ratio of the width to the height of the symbology.
Text labels 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.
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).
Types of icons Refers to the classification of a particular icon based upon its resemblance to the message or referent.
UCS Uniform Chromaticity Scale, a scale, wherein the units of color difference that are judged to be equally different, are separated by nearly equal distance.
User Interface design Refers to the system design characteristics of a computer-based 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.
Visual angle 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.
VDT Visual Display Terminal.
VFD Vacuum Fluorescent Displays
Ways to use icons Refers to the wide variety of options for using an icon to facilitate interaction with an in-vehicle information system (IVIS).
When to use icons 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.

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