Table 1. Recommended values for VMS characteristics; issues and future research needs.

VMS Characteristic:  Letter Height for VMS on Vehicles
Recommended:  Not less than 10 inch

VMS Characteristic:  Letter Height for VMS in Facilities
Recommended:  Not less than 6 inch
Issues and Future Research:
-- VMS legibility distance for 8inch letters has been found to be less than 20 feet for people with
20/80 to 20/160 acuity.
-- Research should be conducted to determine what letter height will optimize reading speed and
legibility distance for individuals with vision impairments reading dynamic messages.

VMS Characteristic:  Width to Height Ratio
Recommended:  0.7 to 1.0
Issues and Future Research:
-- Existing research on this variable is fairly strong and, at a minimum, supports the use of 5x7
versus a 4x7 character matrix.

VMS Characteristic:  Stroke Width to Height Ratio
Recommended:  0.2
Issues and Future Research:
-- Existing research on this variable is fairly strong and supports the use of a 1:5 ratio.

VMS Characteristic:  Text Color
Recommended:  Green or Yellow
Issues and Future Research:
-- Existing research indicates that these two colors provide the best legibility for readers with
vision impairments.
-- Additional research should be conducted to determine if other colors now available in high
brightness LEDs provide any benefit to individuals with vision impairments.

VMS Characteristic:  Font
Recommended:  5x7 for Uppercase  7x9 for Lowercase
Issues and Future Research:
-- Existing research on this variable is fairly strong.

VMS Characteristic:  Luminance
Recommended:  Night: 30cd/m2 Day: >1,000cd/m2
Issues and Future Research:
-- Existing research on this variable is fairly strong for individuals without vision impairments.
-- Additional research should be conducted to determine if these levels are sufficient for
individuals with vision impairments.
-- European standards currently under development should be tracked to determine measurement
methods/recommended levels.

VMS Characteristic:  Luminance Contrast
Recommended:  (Lt-Lb)/Lb = 8 to 12
Issues and Future Research:
--Existing research on this variable is strong for individuals without vision impairments.
--Research should be conducted to determine if these levels are sufficient for individuals with
vision impairments.

VMS Characteristic:  Inter character Spacing
Recommended:  25 to 40% letter height
Issues and Future Research:
-- Existing research on this variable is strong.

VMS Characteristic:  Inter word spacing
Recommended:  75-100% letter height
Issues and Future Research:
-- Existing research on this variable is strong.

VMS Characteristic:  Inter line spacing
Recommended:  50 to 75% letter height
Issues and Future Research:
-- Existing research on this variable is strong.


VMS Characteristic:  Case
Recommended:  Uppercase or mixed case for single words
Recommended:  Lowercase for longer textual messages
Issues and Future Research:
-- Existing research on this variable is strong; however attaining high-quality lowercase
letterforms using a matrix format is difficult. If this cannot be attained, uppercase letters is
preferable.

VMS Characteristic:  Contrast Orientation
Recommended:  Positive
Issues and Future Research:
-- Existing research on this variable is strong for individuals without vision impairments.
-- Research is needed to determine if the findings apply to individuals with vision impairments.

VMS Characteristic:  Sign Width
Recommended:  Dynamic text should be capable of displaying 6-7 characters
Issues and Future Research:
-- Additional research on this variable should be conducted to determine if this basic research
finding holds up in real-world VMS reading by individuals with vision impairments.

VMS Characteristic:  Paging or Streaming
Recommended:  Streaming
Issues and Future Research:
-- Additional research should be conducted.


VMS Characteristic:  Static Display Time
Recommended:  10 Seconds
Issues and Future Research:
-- This is a very weak recommendation and very much in dispute.
-- Additional research must be conducted to determine appropriate reading times for sign
comprehension by individuals with vision impairments.