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

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

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

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CHAPTER 11: LIST OF EQUATIONS

Determining the Appropriate Luminance Uniformity within an Icon

Perent Element (Luminance min) - (Luminance max) (1)
=    
Nonuniformity (Luminance max)  
where  

Luminance max = the smaller luminance value

Luminancemin = the greater luminance value

  

Determining the Appropriate Contrast within an Icon

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

Determining the Appropriate Size of Icon Components

If Known Use These Formulas for Calculating These Known Years
Visual Angle Symbol Height Distance

Distance and

Symbol Height

Symbol height fraction: Symbol Height over Distance

(3)

Symbol height fraction (3438 (Height) over distance) divided by 60

(4)

    

Distance and

Visual Angle

  

Distance x [Tangent (Visual Angle)]

(5)

  

Visual Angle and

Symbol Height

    

Symbol Height

Tangent (Visual Angle)

(6)

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.)

Determining The Effects of Icon Legibility

Figure 3-5. Equation for Determining Color Contrast. Click here for more detail.

S=KOm

Perceived Urgency of Auditory Signals

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)

Figure 6-3. Example of Using Steven's Power Law for Producing Urgency Exponents. This figure is the same as figure 6.3. Click here for more details.

Timing of Auditory Navigation Information

Equations for determining the appropriate timing of an instruction. This figure is the same figure as 6.4. Click here for more details.

Equations for Determining the Appropriate Timing of an Instruction

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