ACCESS BOARD RESEARCH

Synthesis on the Legibility of Variable Message Signing (VMS) for Readers with Vision Loss

May 14, 2002

Philip M. Garvey
The Pennsylvania Transportation Institute
The Pennsylvania State University
University Park, PA 16802

TABLE OF CONTENTS

Executive Summary
Introduction
The Influence of Visual Impairments on VMS Legibility
VMS Legibility Standards and Research
Current VMS Technologies and Applications
Conclusions, Recommendations, and Future Research Needs
References
Appendix A:  Annotated Bibliography
Appendix B:  VMS Guidelines, Standards, and Specifications


Synthesis on the Legibility of Variable Message Signing (VMS) For Readers With Vision Loss: Executive Summary

The use of electronic variable message signs (VMS) to provide traveler information at airports, transit stations, on transit vehicles, along highways, and for pedestrian and driver signaling has increased dramaticallyo ver the past 20 years. The accurate and often real-time information that these devices furnish to travelers in highway and transit environments has made substantial improvements to human centered transportation in the late 20th and early part of the 21st century. However, while much is known about optimizing VMS legibility for people with “normal” vision, and about the legibility of printed text for people who have partial sight, there are still no standards that ensure VMS legibility for either the general population of travelers or for those with visual impairments.

The US Census Bureau (1997) reported that 3.7% of U.S. citizens (7.7 million people) over 15 years of age “had difficulty seeing words/letters,” this jumps to 12.1% for individuals 65 years of age and older. Based on National Center for Health Statistics data it has been estimated that in the United States there are “6.6 million people unable to read printed signs at normal viewing distances.”

The goal of this research project was to gather and synthesize existing information on the legibility of VMS for people with visual impairments with the intent of identifying the features of current and prospective VMS technology that can be improved to better serve the needs of this user group. To realize the project objectives, an extensive literature search was conducted using the Transportation Research Board’s (TRB) Transportation Research Information Services (TRIS), WinSpirs-TRANSPORT transportation literature database, and PsycINFO (via SilverPlatter) using Pennsylvania State University’s LIAS system. However, as publication of research results often takes several years and as much research goes unpublished, a request for information was sent to the Human Factors and Ergonomics Society’s “Surface Transportation” and “Perception and Performance” Technical Groups’ listservs. Messages sent to these listservs go out to nearly 500 professionals in fields related to this research project.

The report begins with a discussion of common visual impairments and how they might affect an individual’s ability to read VMS. This is followed by a detailed review of research on the legibility of VMS in highway and transit applications, and the readability of electronic copy (VMS and non-VMS) for individuals with vision impairments. The final section provides an overview of VMS technologies currently used in transit and the highway environment. A brief description of each technology is accompanied by a discussion of advantages, disadvantages, and use in transit facilities. Two sections are appended to the end of the document. Appendix A contains a detailed bibliography with citations and abstracts. These are divided into two sections: Transportation VMSResearch, and Electronic Text Readability for Individual with Vision Impairments. Appendix B contains an annotated bibliography of state, national, and international VMS design and implementation guidelines and standards.

The research conducted for this report identified the existence of certain design criteria that, if met, will be capable of significantly improving the legibility of VMS for a large percentage of individuals with vision impairments. The question is, are the current findings sufficiently robust to be used to make solid recommendations. In a very recent synthesis on LED/LCD VMS for use on transit vehicles conducted for the Federal Transit Administration (FTA), it was concluded that there was sufficient available guidance on several indices, including: the position of on-vehicle VMS; character height; width-to-height ratio; stroke width-to-height ratio; and inter-character spacing. Conversely, the FTA study stated that there were insufficient data regarding: visibility under varying lighting conditions; streaming and paging style and rate; sign color; relative motion between the sign and the observer; and glare effects.

The present report supports the FTA study conclusions regarding the need for further research to fill the gaps they identified, particularly with regard to paging and streaming rates and time allotted for individuals with vision impairments to read VMS. This report however demonstrates that other issues (e.g., letter height, color, and luminance), alone and in combination, may still benefit from additional study. In particular, appropriate letter heights should be developed using new, brighter light emitting VMS, in combination with streaming text for subjects who have a variety of functional visual impairments (e.g., scotoma, CFL, and PFL). Furthermore, the use of an analytical model to determine letter heights (as suggested in the FTA research and elsewhere) does not address the complexity of VMS reading by individuals with vision impairments in real-world environments. A summary of recommendations regarding the application of current knowledge to future VMS design, and recommendations for future research to fill the gaps in that current knowledge can be found in Table 1.

Table 1.Recommended values for VMS characteristics; issues and future research needs. (Text Version)

VMS Characteristic Recommended Issues and Future Research
Letter Height for VMS on Vehicles Not less than 10 inch -- 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.
Letter Height for VMS in Facilities Not less than 6 inch
Width to Height Ratio 0.7 to 1.0 -- Existing research on this variable is fairly strong and, at a minimum, supports the use of 5x7 versus a 4x7 character matrix.
Stroke Width to Height Ratio 0.2 -- Existing research on this variable is fairly strong and supports the use of a 1:5 ratio.
Text Color Green or Yellow -- 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.
Font 5x7 for Uppercase

7x9 for Lowercase
-- Existing research on this variable is fairly strong.
Luminance Night: 30cd/m2

Day: >1,000cd/m2
-- 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.
Luminance Contrast (Lt-Lb)/Lb = 8 to 12 --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.
Inter character Spacing 25 to 40%

letter height
-- Existing research on this variable is strong.
Inter word spacing 75-100%

letter height
-- Existing research on this variable is strong.
Inter line spacing 50 to 75%

letter height
-- Existing research on this variable is strong.
Case Uppercase or mixed case for single words -- 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.
Lowercase for longer textual messages
Contrast Orientation Positive -- 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.
Sign Width Dynamic text should be capable of displaying 6-7 characters -- 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.
Paging or Streaming Streaming -- Additional research should be conducted.
Static Display Time 10 Seconds -- 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.

INTRODUCTION

Overview

The use of electronic variable message signs (VMS) to provide traveler information at airports, transit stations, on transit vehicles, along highways, and for pedestrian and driver signaling has increased dramatically over the past 20 years. The accurate and often real-time information that these devices furnish to travelers in highway and transit environments has made substantial improvements to human centered transportation in the late 20th and early part of the 21st century. However, while much is known about optimizing VMS legibility for people with “normal” vision, and about the legibility of printed text for people who have partial sight, there are still no standards that ensure VMS legibility for either the general population of travelers or for those with visual impairments.

In the early to mid 1990’s there were a large number of Federally funded research projects aimed at assessing VMS legibility and developing guidelines for their use (e.g., Dudek, 1991, 1997; Upchurch, Armstrong, Baaj, and Thomas, 1992; Bentzen, Easton, Nolin, and Mitchel, 1994; Bentzen and Easton 1996; and Garvey and Mace, 1996). Dudek (1997) synthesized much of the highway research for the National Cooperative Highway Research Program (NCHRP) and the findings directly related to the legibility of transit VMS for individuals with vision impairments were summarized by Hunter-Zaworski (1994) for the Federal Transit Administration (FTA). While much of this research is still valid, due to recent advances in VMS technology a good deal of it is no longer current.

Objectives

The goal of this research project was to gather and synthesize existing information on the legibility of VMS for pple with visual impairments with the intent of identifying the features of current and prospective VMS technology that can be improved to better serve the needseo of this user group.

Satisfying Objectives

Obstacles

Unfortunately, most VMS legibility research has been conducted in the highway environment where visual impairment is kept to a minimum by licensure restrictions. Of course, once a driver has a license their vision is rarely retested. There are, therefore, many drivers with visual impairments that have occurred since their initial licensure. Nominally, however, licensed U.S. drivers have high contrast distance visual acuity of 20/40 or better and, because of this restriction, the Federal Highway Administration (FHWA) only requires signs to accommodate relatively high visually functioning individuals.

This is typically not seen as a problem. As vision plays such a large role in driving, the general consensus is that high standards of visual performance are desirable. However, as a result research on highway VMS does not include a visually impaired component. While it is true that most human factors research conducted on highway VMS in the past decade has involved older drivers as subjects to account for age-related losses in vision (e.g., Garvey and Mace, 1996; Upchurch, et al., 1992), the recommendations still do not go beyond visual acuities of about 20/50 and never approach the type or extent of visual impairments that are found in other VMS reading environments such as transit.

Overcoming Obstacles

Despite these limitations, research conducted in the highway environment withnon visually impaired observers can still be used to describe VMS characteristics that contribute to legibility for all readers, regardless of their visual abilities (e.g., increasing letter height and luminance contrast will help almost everybody). However, to accomplish the specific goal of synthesizing VMS legibility requirements for readers with vision impairments, the literature review conducted for this report had to go beyond the evaluation of transportation research to include the more basic visual impairment research being conducted in the fields of psychology, ophthalmology, and psycholinguistics.

To realize the project objectives, an extensive literature search was conducted using the Transportation Research Board’s (TRB) Transportation Research Information Services (TRIS), WinSpirs-TRANSPORT transportation literature database, and PsycINFO (via SilverPlatter) using Pennsylvania State University’s LIAS system. However, as publication of research results often takes several years and as much research goes unpublished, the current knowledge in any field is in the minds and hands of the people working in that field. Therefore, a request for information regarding this topic was sent to the Human Factors and Ergonomics Society’s “Surface Transportation” and “Perception and Performance” Technical Groups’ listservs. Messages sent to these listservs are received by nearly 500 professionals in fields related to this research project.

Note on Usage

With the Millennium edition of the Manual on Uniform Traffic Control Devices (MUTCD, 2000), the highway community officially adopted the term Changeable Message Signs (CMS) for the type of signs researched in this report. The transit community mainly calls these devices Variable Message Signs (VMS) but also uses Passenger (or Customer) Information Systems and Passenger Information Displays, while the intelligent transportation systems (ITS) community commonly uses the term Dynamic Message Signs (DMS). For the purposes of continuity, the term VMS will be used throughout this report unless another source is quoted.

Report Strategy

The remainder of this report begins with a discussion of common visual impairments and how they might affect an individual's ability to read VMS. This is followed by a detailed review of research on the legibility of VMS in highway and transit applications, and the readability of electronic copy (VMS and non-VMS) for individuals with vision impairments. The final section of this report is an overview of VMS technologies currently used in transit and the highway environment. A brief description of each technology is accompanied by a discussion of their advantages, disadvantages, and use in transit facilities. The scope of the project did not allow for a survey of transit authorities to be conducted, therefore the VMS transit applications were obtained from the literature review. Because of delay in publishing, statements regarding transit authorities’ use of VMS will mainly reflect usage in the mid to late 1990’s, with a small number of references to the early part of the 21st century.

Two sections are appended to the end of the text document. Appendix A contains a detailed bibliography with citations and abstracts. These citations are divided into two sections: Transportation VMS Research, And Electronic Text Readability for Individuals with Vision Impairments. Appendix B contains an annotated bibliography of state, national, and international VMS design and implementation guidelines and draft standards.


THE INFLUENCE OF VISUAL IMPAIRMENTS ON VMS LEGIBILITY

Extent of the Problem

The World Health Report (1998) estimated that there are almost 45 million blind people worldwide. Of those, 43% lost their vision due to cataracts, 15% from glaucoma, 11% by trachoma, 6% were children under the age of five with vitamin-A deficiency, and 24% were caused by a combination of diabetic retinopathy, macular degeneration, optic neuropathy, and other causes. The World Health Organization (2002) reported that worldwide there are approximately 180 million persons with vision disabilities and 40 to 45 million blind (blind defined as "cannot walk about unaided").

The US Census Bureau (1997) reported that 3.7% of U.S. citizens (7.7 million people) over 15 years of age “had difficulty seeing words/letters,” this increases to 12.1% for individuals 65 years of age and older. Klien (1991) reported that the leading causes of visual impairment in the U.S. were age related macular degeneration (24%), open-angle glaucoma (14%), cataract (13%), and diabetic retinopathy (8%). Based on National Center for Health Statistics data, Bentzen, Crandall, and Myers (1999) estimated that in the United States there are “6.6 million people unable to read printed signs at normal viewing distances.”

Definitions

Although clinical diagnoses like those noted above can be useful, Legge and Rubin (1986) made the following critical observation: “It has been shown that visual criteria [e.g., presence or absence of central vision] are better than medical diagnoses [e.g., diabetic retinopathy] for predicting the success rates for the utilization of low-vision reading aids. We are concerned with the effects of visual abnormalities, whatever their cause, on reading performance. We have found that reading performance can be predicted from visual measures that transcend diagnostic categories.” Lovie-Kitchin, Bowers,and Woods (2000) took Legge and Rubin’s functional distinctions a step further including near and far visual acuity, and measures of scotoma size and position. While there are many ways to functionally describe vision loss, the Community Services for the Blind and Partially Sighted (2002) listed the following useful definitions:

Visual Impairment:Trouble seeing with one or both eyes even when wearing glasses or contacts.

Severe Visual Impairment:Inability to read ordinary newsprint even with the best correction (glasses or contact lenses).

Low Vision: Vision that cannot be further improved by corrective lenses or medical or surgical intervention, although low vision rehabilitation may help someone to use remaining sight more effectively.

Legal Blindness: A central visual acuity for distance of 20/200 or poorer in the better eye with correction, or a field of vision no greater than 20 degrees in widest diameter.

Functional Blindness: No useful vision; clinically measured light perception or less.

Impact of Vision Loss on Sign Legibility

Visual Acuity

Vision loss is a rather vague term that, as the definitions above attest, can be characterized in many ways. The critical relationship between visual impairment and sign legibility, however, is often portrayed as a loss in visual acuity (e.g., “A person is termed legally blind when their visual acuity…is 20/200 or worse after correction…” -- Wourms, Cunningham, Self, and Johnson, 2001). While poor visual acuity is not the only functional deficit associated with visual impairment, it is clearly a significant factor in sign legibility.

Visual acuity can be broadly defined as the ability to discriminate fine detail, but what fine details are required for VMS legibility? When testing visual acuity with acuity optotypes, such as Snellen letters, Landolt C’s, and Lazy E’s, the critical detail is assumed to be stroke-width. The visual angle of the stroke-width at the test distance is considered to be the minimum angle of resolution (MAR) and is used to describe visual acuity. With Snellen letters, for example, the stroke-width is equal to 1.0 arcmin (1/60th of a degree) on the 20/20 line (logMAR = 0.0), and the letter height is 5.0 arcmin (1:5 stroke-width-to-height ratio).

A number of researchers have used MAR to predict sign legibility distance for a range of individual visual acuities (e.g., Howett, 1983; Colomb, Hubert, Carta, Bry, and Dore-Picard, 1991; and Wourms, et al. 2001). These efforts boil down to the application of a simple trigonometric calculation (A = arctan C/D). Where A isMAR, C is size of the critical detail, and D is the viewing distance. Table 1 contains legibility distances calculated in this fashion for letter heights ranging from one to eight inches, standard VMS stroke-width-to height ratios of 1:5 and 1:7, and acuities from 20/10 to 20/400.

This is a clean analytic tool based on principles of visual perception and trigonometry; however, while it is not surprising that sign legibility is correlated with visual acuity, it is not true to infer that the relationship is as straightforward as Table 1 implies. The reason for this is that sign reading is not the same as acuity chart reading. There are two main differences between acuity charts and signs. First, acuity charts test high contrast black symbols on white backgrounds while signs vary in contrast, are designed using both positive and negative contrast orientation, and use many different colors. Second, acuity charts test very special letters or symbols (i.e., optotypes) with specific characteristics, and signs use words, sentences, and phrases.

Font

Letters used on signs are different than the stimuli used on acuity test charts and, because of this, sign legibility distances cannot be accurately predicted from measures of visual acuity. Garvey, Zineddin, and Pietrucha (2001) found that stroke-width resolution alone does not determine letter acuity, even with fairly simple letterforms and high visual functioning observers (i.e., acuity better than or equal to 20/40). These researchers replaced the letters on a standard Snellen chart with letters displayed in thirteen different fonts. They found that to be read at the same distance, letters in some fonts had to be twice the height of letters in other fonts. Mean acuity for the Snellen letters was 20/16 and acuity for the other fonts ranged from 20/12 to 20/30. Furthermore, the differences were a function of a complex combination of letter attributes and not stroke width alone. This study illustrates the lack of generalizability of measured acuity to other test or sign fonts. To complicate matters further, in a follow-up study, Zineddin (2002) found that acuity can be influenced by familiarity with the test stimuli, and that subjects’ acuity for a given font could actually improve with practice.

Word/Sentence

Another reason for the lack of correspondence between MAR and sign reading is that signs use words, sentences, and phrases, and not merely strings of letters. Word legibility introduces cognitive factors quantitatively and qualitatively different from those posed by letters. Sentence reading takes this a step further as mentioned by Legge, Ahn, Klitz, and Luebker (1997) who stated that reading speed for words in sentences could be faster than for single words because of the “predictability of the words in sentences.” Fine, Peli, and Reeves (1997) suggested that this was due in part to the additional information provided by syntactic and semantic sentence content. Because of these cognitive components, sign message recognition does not require the ability to discriminate all content elements (e.g., every stroke of a letter or even all the letters in a word, or words in a sentence or phrase) for correct message identification to occur (Proffitt, Wade, and Lynn, 1998). Familiar word recognition has been shown to be based more on global features such as overall shape or “footprint” (Garvey, Meeker, and Pietrucha, 1998) than on letter characteristics. As a result, at least for normally sighted individuals, sign legibility distances are longer than would be predicted by either visual acuity or sign characteristics alone (Kuhn, Garvey, and Pietrucha, 1998). This is known as the word superiority effect (for a review see Zineddin, 2001). The extent of this effect on VMS reading for individuals with vision impairments has not been evaluated.

Table 2.Legibility distance (in feet) for various letter heights, stroke-width-to-height ratios, and visual acuities.

Visual Acuity MAR (arcmin) Stroke-Width-to-Height Ratio 1:5

Letter Height (in)
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00
20/10 0.50 114.6 229.2 343.8 458.4 573.0 687.6 802.2 916.8
20/20 1.00 57.3 114.6 171.9 229.2 286.5 343.8 401.1 458.4
20/40 2.00 28.7 57.3 86.0 114.6 143.3 171.9 200.6 229.2
20/60 3.00 19.1 38.2 57.3 76.4 95.5 114.6 133.7 152.8
20/80 4.00 14.3 28.7 43.0 57.3 71.6 86.0 100.3 114.6
20/100 5.00 11.5 22.9 34.4 45.8 57.3 68.8 80.2 91.7
20/150 7.50 7.6 15.3 22.9 30.6 38.2 45.8 53.5 61.1
20/200 10.00 5.7 11.5 17.2 22.9 28.7 34.4 40.1 45.8
20/250 12.50 4.6 9.2 13.8 18.3 22.9 27.5 32.1 36.7
20/300 15.00 3.8 7.6 11.5 15.3 19.1 22.9 26.7 30.6
20/350 17.50 3.3 6.5 9.8 13.1 16.4 19.6 22.9 26.2
20/400 20.00 2.9 5.7 8.6 11.5 14.3 17.2 20.1 22.9

 

Visual Acuity MAR (arcmin) Stroke-Width-to-Height Ratio 1:7
Letter Height (in)
1.00 2.00 3.00 4.00 5.00 6.00 7.00
20/10 0.50 81.9 163.7 245.6 327.4 409.3 491.1 573.0
20/20 1.00 40.9 81.9 122.8 163.7 204.6 245.6 286.5
20/40 2.00 20.5 40.9 61.4 81.9 102.3 122.8 143.3
20/60 3.00 13.6 27.3 40.9 54.6 68.2 81.9 95.5
20/80 4.00 10.2 20.5 30.7 40.9 51.2 61.4 71.6
20/100 5.00 8.2 16.4 24.6 32.7 40.9 49.1 57.3
20/150 7.50 5.5 10.9 16.4 21.8 27.3 32.7 38.2
20/200 10.00 4.1 8.2 12.3 16.4 20.5 24.6 28.7
20/250 12.50 3.3 6.5 9.8 13.1 16.4 19.6 22.9
20/300 15.00 2.7 5.5 8.2 10.9 13.6 16.4 19.1
20/350 17.50 2.3 4.7 7.0 9.4 11.7 14.0 16.4
20/400 20.00 2.0 4.1 6.1 8.2 10.2 12.3 14.3

Reading Speed

While sign legibility has been the major focus of VMS readability research, it is not the only measure of sign performance. Reading speed also has a dramatic impact on the effectiveness of VMS, which are designed to present information in a sequential format. Research evaluating “optimum acuity reserve” (the ratio between threshold acuity and optimal print size) has demonstrated that the best possible reading speeds result from print size that may be as much as four times size threshold (Bowers and Reid, 1997; Yager, Aquilante, and Plass, 1998; Lovie-Kitchin, et al. 2000). In fact, Yager et al. (1998) reported that reading speed at size threshold is 0.0 words per minute (wpm) increasing linearly with log letter height (average reading speeds is approximately 250 wpm). Calculations such as those shown in Table 1 however, only provide letter height thresholds and do not take reading time into consideration. Based on text reading research, the letter heights in Table 1 (even if they accurately predict sign reading) would need to be increased by a factor of four to optimize reading performance.

Other Visual Impairments

While central vision is, of course, critical to reading ability, deficits in peripheral vision and the presence and position of localized scotoma also impact an individual’s ability to read VMS (Raasch and Rubin, 1993).Scotomata are “small area[s] of abnormally less sensitive or absent vision in the visual field, surrounded by normal sight…islands of total visual loss in other parts of the field are referred to as absolute scotomata.A relative scotoma is a spot where the vision is decreased but still present” (Concise Medical Dictionary, 1998). Research discussed below in the section on streaming text demonstrates that these impairments can result in a reduction in reading speed.

Summary

While an analytic solution to the problem of attaining appropriate letter height for various acuity populations (e.g., Table 1) is enticing, to truly determine VMS readability for the population of individuals with vision impairments it is necessary to evaluate real-world sign reading by individuals with visual deficits.


VMS LEGIBILITY STANDARDS AND RESEARCH

Dudek (1997) surveyed 27 states to determine whether they had design standards to optimize VMS legibility distance. He found that 14% specified luminance contrast ratio between legend and sign background, 36% specified external and internal illumination, 46% character height, and 39% had specifications for character width, and spacing between characters and lines of text. Dudek cited the lack of national standards and the relative novelty of VMS as reasons for the low percentage of state standards. Marston (1993) wrote that because of knowledge gaps regarding recent product developments often a “state or local agency writes the specification so generally that any CMS project or technology is applicable.”

There are no validreasons, however, for the lack of state and national design standards to ensure VMS legibility. There have been hundreds of research projects conducted since the 1950’s that address related visibility issues in static sign legibility and dozens conducted since the 1970’s that directly address the legibility of VMS. There are numerous reports that have listed the critical attributes that influence VMS legibility, tested those attributes under day and night conditions with young and old observers, and provided recommendations regarding optimal, minimal, and acceptable design standards for various criteria. Many of these findings are based on principles of visual perception that were then field tested on actual VMS. Most of these findings are applicable regardless of VMS technology type (Garvey and Mace, 1996).

The following sections consist of a summary of those research results and recommendations as well as VMS requirements found in several specification, guideline, and standards publications (the latter are further detailed in Appendix B). Although most of the research did not address issues related to special user populations, an attempt was made to synthesize the general findings with those that did test VMS with subjects with vision impairments. Special emphasis is placed on how these recommendations and requirements relate to VMS legibility for individuals with vision impairments.

Note: The majority of VMS legibility research has been conducted on signs that use a matrix design and most of the recommendations are, therefore, couched in the terms related to this type of VMS. Also, VMS legibility is the result of the interaction of all the character variables discussed below; for example, while large letter heights might be desirable they will not be visible at appropriate distances if they are displayed at low contrast.

Character Variables

Letter Height

Letter height is perhaps the first sign characteristic manipulated when attempting to improve VMS legibility. This is because (if all other characteristics are appropriate) letter height has the greatest impact on the distance at which a sign can be read (Garvey and Mace, 1996). Unlike other key variables (e.g., contrast, luminance, and stroke width) legibility distance continues to improve with increases in letter height; there is no practical asymptote. There are, however real world limitations on sign size, and there is also research that reports letter heights that result in optimal reading speeds above which performance declines (Raasch and Rubin, 1993).

On Vehicles

Although the Americans with Disabilities Act Accessibility Guidelines (ADAAG) requirements for sign design do not specify VMS, they are meant to apply to all public access signage. The ADAAG requirements state that for public transportation vehicles, “Characters on signs...shall have a…minimum character height (using an upper case "X") of 1 inch for signs on the boarding side and a minimum character height of 2 inches for front headsigns.” The American Public Transit Association (APTA) states, “front destination signs shall have…a message display area of not less than 9.8 inches high…” and “side destination signs shall have…a display area of not less than 3.15 inches high…” (in Wourms, et al., 2001). This is consistent with the Public Service Vehicle Accessibility Regulations 2000 which require signs in the front of the vehicle to be no less than 8 inches in height and no less than 2.8 inches on the side of vehicles (in Wourms, et al., 2001).

The later requirements are in better agreement with empirical research findings than those of the ADAAG. Bentzen, et al. (1994) in a study where films of buses with reflective disk VMS displayed on the front and side found that 8 inch letters were read further away than 6 and 4 inch letters and that 6 in letters were legible at a greater distance than 4 inch letters for subjects with vision loss. Even with the 8 inch letters, though, on average the group with intermediate visual impairment (20/80 to 20/160) was only able to read the front mounted signs at a little over 20 feet. The eight-inch signs in this study had a stroke width of 1.2 inches resulting in a stroke width to height ratio of about 1:7.A comparison of these empirical results with the predictions in Table 1 show an overestimation in the analytical model, which calculates 40 to 82 feet of legibility distance for this group of subjects. Bentzen, et al.’s subjects with visual acuities between 20/200 and 20/400 only correctly identified the sign message under these conditions approximately 20% of the time.

In Facilities

ADAAG requires signs in public and commercial facilities to have “Minimum character height of 3 inches”” (ADAAG, 1994: Section 4.30 “Signage”). However, in studying VMS legibility Bentzen and Easton (1996) found that while 2 inch high character LED VMS resulted in 85% accuracy for low vision subjects, accuracy dropped to 66% for legally blind individuals at reading distances as close as three to thirty-three feet.

On Highways

For freeways, Dudek (1997) recommended a character height of 18 inches and between 10 and 18 inches for non-freeway applications. Garvey and Mace (1996) found proportional improvement in legibility distance with increased letter height up to about 8 inches, above which there was some drop-off in improvements.

Legibility Index (LI)

LI is a measure of the legibility distance of a sign as a function of letter height and is expressed in feet per inch of letter height (ft/in). Upchurch, et al. (1991) and Garvey and Mace (1996) found that LIs on the order of 35 ft/in would accommodate “average” older and younger observers. This means that for every inch of letter height, the subjects could read the VMS 35 feet away. However, Garvey and Mace found a significant reduction in daytime legibility with their poorest performing subjects, where LIs dropped to 22 ft/in for the 85th percentile younger subjects and 17 ft/in for the 85th percentile older groups. The situation is even worse for the truly visually impaired. Based on previous research by Muller-Munk (1986),Bentzen et al. (1994) estimated that LIs for the legally blind would more closely approximate 3 ft/in, which translates into ten-inch letter heights at 30 feet just to reach threshold.

Letter Width

The ADAAG requirements specify that “Characters on [transportation vehicle] signs...shall have a width-to-height ratio between 3:5 and 1:1.” Garvey and Mace (1996) found an improvement in VMS legibility distance with increases in width-to-height ratio (w:h) up to 1:1, or letters having equal width and height. Dudek (1991) reported that a 5x7 (w:h 5:7) matrix is slightly more legible than a 4x7 (w:h 4:7) matrix. Wourms, et al., (2001) found a recommendation that ranged from 3:5 to 4:5 (Woodson, 1981). Using subjects with vision impairments, Bentzen and Easton (1996) found slightly better performance with a 5x7 character LED VMS than a 6x7 character.

Stroke Width

ADAAG specifications state, “Characters on [transportation vehicle] signs...shall have a… stroke width-to-height ratio between 1:5 and 1:10.” Wourms, et al., (2001) reported Saunders and McCormick’s (1993) recommendation, which ranged from 1:6 to 1:8. Stroke width for matrix VMS interacts directly with the width to height ratio discussed above. Although some form of double-stroke is possible on many models, typically VMS matrices have a stroke width equal to a single element. Therefore, for example, 5x7 VMS will typically have a stroke width to height ratio of 1:7.

Color

Garvey and Mace (1996) studied VMS with red, white, and yellow elements and found no significant difference in VMS legibility for normal vision subjects. When Legge and Rubin (1986) tested non visually impaired subjects they also found no color effects when the letters were large, although they did find some small effects when the letters were near size threshold.

Legge and Rubin (1986) also tested subjects with vision impairments and found that the protanopic subjects showed “major reduction in sensitivity to red” while the deuteranopic subjects showed no change in legibility with color. Furthermore, subjects in their study who had photoreceptor degeneration performed better in blue or green than red with highest performance being achieved with the green letters. In studying the daytime legibility of LED VMS mounted within buses, Bentzen and Easton (1996) found a color effect for both subjects with vision impairments and those without under certain viewing conditions. When one-word messages were streaming at a fast rate (2.56 sec dwell), green signs were read more accurately than red signs,this finding was not evident with the slower streaming rate of 2.74 sec dwell (longer dwell means slower speed) or with static presentation. In addition to these objective results, they found a strong stated preference for the green VMS.

Legge and Rubin (1996) recommended green or gray letters stating, “these are the colors best suited for the design of reading displays for subjects with normal or low vision.” Marner (1991) reported that the U.K Royal National Institute for the Blind highly recommended yellow characters on a black background, while Schofield and Flute (1997) cited recent research suggesting people with visual impairments preferred white on deep navy blue (in Wourms, et al. 2001).

Font

Garvey,Pietrucha, and Meeker (1997, 1998,2001) and Garvey, Zineddin,and Pietrucha (2001) have demonstrated that font can have a dramatic affect on standard highway sign legibility and, as mentioned previously, on large format letter legibility. Yager, et al. (1998) concluded that font can have an effect on reading speed when the letter heights and luminance contrast are close to threshold, they went on to state, “Until systematic comprehensive studies are done,choices of font characteristics for low vision reading will depend on uninformed biases and, perhaps, aesthetic considerations rather than optimization of performance.”

There is not, however, a great deal of flexibility in VMS font design as these signs are often restricted by a matrix format. Garvey and Mace (1996),Dudek (1991), and Bentzen and Easton (1996) all recommended fonts displayed using a 5x7 character matrix for VMS. Garvey and Mace found little variability in performance using different fonts within the 5x7 format. The Guidelines for Transit Facility Signing and Graphics (in Wourms, et al., 2001) recommend using a minimum of 7x9matrix and also state that a double stroke must be used. The latter recommendation, though, contradicts research findings (Garvey and Mace, 1996) of a 25% reduction in legibility distance with double fonts versus a single stroke font used within a 5x7 character matrix. The double font used in the Garvey and Mace research was, however, not a true double font as some of the letter strokes had only a single stroke width (for example the horizontal bars of the E were single stoke while the vertical bar was double). It is possible that a full double stroke font could provide better legibility, but many 5x7 character VMS are not capable of producing these.

Luminance

Garvey and Mace (1996) recommended nighttime luminance of30 cd/m2 and 1000 cd/m2 for bright daytime viewing. They found, however, that as visual acuity worsened, more light was needed to achieve equivalent performance. Dudek's (1991) nighttime luminance recommendation was from 30to 230 cd/m2. The European highway community has been attempting to derive standard optical test methods for VMS for the past 15 years, but have been slowed down by, among other factors, rapidly changing technology (Grahame Cheek, European Standards body (CEN), March 8, 2002: personal communication). There currently are no photometric standards to specify what aspect of the sign should be measured (for a discussion on the issues, see Garvey and Mace, 1996; or Lewis,2000).

Luminance Contrast

Combining the results of six research efforts on static traffic sign legibility, Sivak and Olson (1985) derived a recommended contrast ratio of 12:1 for positive contrast signs. Staplin, et al. (1997) expanded this to between 4:1 and 50:1. On VMS, Colomb and Hubert (1991) found improvements in daytime legibility to level off between 8 and 20 percent contrast. Stainforth and Kniveton (1996) reported that generally accepted luminance contrast ratio for VMS is 10:1. Dudek (1991) stated that for VMS, contrast ratio between 8:1 and 12:1 should be used for light emitting technologies and 40% daytime and 50% nighttime contrast for light reflecting technologies. The “Passenger Information Services: A guidebook for Transit Systems” recommends 70% contrast for all signs (Wourms et al. (2001). At extremely low contrast (less than 10%) Legge, Ahn, Klitz, and Luebker (1997) found reduction in reading speed.

Letter, Word, and Line Spacing

"Characters on [transportation vehicle] signs…shall have…"wide" spacing (generally, the space between letters shall be 1/16 the height of upper case letters)” (ADAAG, 1991). This is an extremely narrow spacing, which is not supported by experimental research with or without visually impaired subjects. Garvey and Mace (1996) tested inter-letter and inter-word spacing in computer simulated matrix VMS words and found that the "single element" inter-letter spacing (1/7 letter height) produced the poorest results. They recommended a minimum spacing of 3/7th letter height, or almost seven-times that required by the ADAAG. Dudek (1991), in summarizing European VMS standards, wrote that the desirable inter-character spacing is 2/7th letter height and line spacing is 4/7th letter height. Mace and Garvey (1996) found an inter-line spacing of 75% to be best for three-line signs, but noted that this was probably excessive for signs displaying only two lines. Woodson (1993), reported that inter character spacing should be between 25 and 50 percent of character height and inter word spacing should be from 75 to 100 percent of letter height (in Wourms,et al. 2001).

Case

The ADAAG requirements read, “Lower case characters are permitted” (ADAAG, 1994). Research by Garvey, et al. (1997, 1998) support this statement by demonstrating that for highway signs lower case words are more legible (by 12 to 15%) than uppercase for word recognition. They also found that upper case and lower case words perform equally well for word legibility, where individual letter reading is required. The “Passenger Information Services: A guidebook for transit systems” stated that uppercase letters should be used for destinations and other short messages, and mixed case should be used for “long legends and instructions,” and the Public Service Vehicle Accessibility Regulations (2000) state, “Destination information shall not be written in capital letters only” and that “the use of both upper and lower case text helps ensure that words that are not completely clear and legible to people with a degree of vision impairment or learning disability, are still identifiable through shape recognition of the word.” (in Wourms, et al., 2001). Dudek (1991) made an important practical argument, however, when he pointed out that for matrix signs, a 7x9 character matrix is required to produce reasonable lower case fonts, and because of this he recommended using upper case letters.

Contrast Orientation (or Polarity)

Positive contrast signs have light letters on dark backgrounds and negative contrast signs have dark letters on light backgrounds. This terminology results from using the contrast ratio Lt-Lb/Lb where Lt is the luminance of the “target” (or in the case of signs, the letters) and Lb is the background luminance. While the ADAAG sign requirements state “Characters on [transportation vehicle] signs…shall…contrast with the background, either dark-on-light or light-on-dark” (ADAAG, 1991), Garvey and Mace (1996) reported a 29% improvement in nighttime VMS legibility distance with positive versus negative contrast messages. Positive contrast is also recommended by Iannuzziello (2001) for general transit signage.

Sign Width

Peli and Fine (1996) found that individuals with vision impairments (median acuity of 20/100) need a larger “window” than their normal vision counterparts to read streaming text. While non-visually impaired subjects in their study performed well with a window of about four to five letters, those with vision impairments required six to seven letters for optimal performance.

Display Variables

VMS often present more information than will fit on a single display. The messages must therefore be displayed in a dynamic format, either by paging or by some form of scrolling or streaming. Paging means that the information is static, but a number of pages of information are shown sequentially to convey the entire message. Scrolling typically denotes that the text is moving down the sign from the top to the bottom. Streaming refers to text that moves across the sign from the right to the left. Streaming is the method used most frequently with single line message boards.

Although the capability of providing a large amount of information in a small space is part of what makes VMS such useful tools, the necessity of paging, scrolling, and streaming also presents some unique challenges when attempting to accommodate readers with vision impairments. Perhaps one of the most important considerations in this regard is reading speed. Legge, et al., (1997), stated that people with visual impairments read more slowly than their sighted counterparts even with visual aids such as magnification and high contrast materials. They stated that the slower reading is due to reduced visual span (number of letters legible in a fixation), which results in smaller eye movements and longer fixation duration. Unfortunately, researchers have yet to reach consensus on how best to display dynamic information to individuals with vision impairments.

Paging or Streaming

In evaluating LED next-stop VMS on buses, Bentzen and Easton (1996) found that, “static messages were clearly superior to streaming messages.” However, some messages are too large to fit on a single display.Bentzen and Easton (1996) found that when this was the case streaming messages outperformed paging messages. However, Kang and Muter (1989) reported earlier research (Sekey and Tietz, 1982) that found reading speed to be slower for constant scrolling (i.e., Times Square) than either “saccadic scrolling or page mode.” Their ownresearch, supports that of Bentzen and Easton (1996) and they concluded that scrolling works as well as static techniques and is “preferred by readers.” With regard to readers with vision impairments, however, they went on to quote Williamson, et al.’s (1986) suggestion that static presentation may help those with peripheral field loss because it “paces readers and prevents [eye movement] regressions.” Fine, et al. (1997) disputed this in reporting that subjects with vision impairments did not show any improvement with static presentations (i.e., rapid serial visual presentation or RSVP) over dynamic or scrolling text. They stated that unlike people with normal vision, those with central field loss (CFL) make eye movements during static presentations, which slows reading speed. In 1996, Fine and Peli took this a step further when they suggested that individuals with CFL might actually benefit from dynamic text, because tracking the text might help to stabilize their eye movements. As recently as 2001, however Wourms, et al. wrote, “Scrolling information is very difficult for a person who is visually impaired to read, text should be displayed in a fixed manner if possible.”

Display Time and Speed

How long a static message should be displayed and how fast a dynamic message should stream across the sign is mainly a function of the target audience’s reading rate. Proffitt, et al. (1998) stated, “The average adult reads about 250 words per minute (wpm) during normal reading.” Kang and Muter (1989) put the rate at 280 wpm for college students. On the other hand, Lovie-Kitchin, et al. (2000) reported that the mean silent “rauding” rate (reading for comprehension) for a group of subjects with macular degeneration was 105 wpm while the oral rate was 79 wpm. Krischer and Meisser (1983) however, stated that it was impossible to determine the reading speed of individuals with vision impairments as a group because of the heterogeneity of the population and the fact that reading speeds are highly dependent on the functional type of impairment. Their own research provided evidence for this when it revealed that central scotoma has “by far” the largest effect on reading speed, and that individuals with peripheral field loss had relatively fast reading rates.

Perhaps mainly because of the reasons mentioned by Kricher and Meisser (1983), there are numerous and varied recommendations regarding both VMS message duration and speed. It has been recommended that, “a line of text should be displayed for at least ten seconds, preferably a little longer.”(ECMT, 1999). Dudek, 1991 recommended a minimum exposure time of “one second per short word… or two seconds per unit of information” for use with unfamiliar drivers. Harris and Whitney (1993) wrote that if scrolling is used, information should be left on the screen for at least twice the normal reading time. Barham, Oxleuy, and Shaw (1994) found a fixed time of about 10 seconds to avoid confusion and recommended message display from 10 to 20 seconds (in Wourms, et al., 2001). Joffee (1995) recommended a display time of 1.6 seconds when a VMS must display multiple pages of information. Finally, when Bentzen and Easton evaluated two streaming rates (i.e., 2.75 and 2.56 sec dwell times) they found that, while there was no main effect, the faster rate interacted negatively with both color and sign height. Furthermore, in their focus group study these researchers found that a dwell time of 3.5 sec was so slow as to appear to flicker and a dwell time of 1.5 sec was too fast for subjects to consistently read the message.


CURRENT VMS TECHNOLOGIES AND APPLICATIONS

The ability to electronically change a sign's message has existed for many years, however it was not until the 1970's that the matrix design so common today enabled signs to display “free text programmability” (Stainforth and Kniveton, 1996), or the ability to display any textual message desired.(A review of the history of VMS usage on North American and European highways can be found in Dudek, 1991).

Willis (1995) reported that the VMS technologies used in transit are reflective disk (RD), liquid crystal (LCD), light emitting diode (LED), and television monitors. While there are many different types of VMS, they can be placed into three major functional categories based on how the sign messages are illuminated: light reflecting; light emitting; and hybrid (Dudek, 1997). Each group has benefits and drawbacks with regard not only to visibility but also price, maintenance, message flexibility, color rendition, and many other variables. A thorough description and evaluation of VMS transit applications was published in 1996 as “TCRP Report 12: Guidelines for Transit Facility Signing and Graphics” (Earnhart). Much of the information in that document holds true today and will form the foundation of this section. Given the rapid growth of VMS design technologies, however, there have been some dramatic advances and performance improvement since that document was written, particularly with the light emitting and hybrid VMS. Therefore, the information from Earnhart (1996) will be supplemented with as much recent data as was available at the writing of this report.

Jenkins (1991), Upchurch, et al. (1992), and Garvey and Mace (1996) evaluated the relative legibility of various VMS technologies and found that, in general, VMS that used either light emitting or a combination of light emitting and light reflecting technologies (hybrids) outperformed light reflecting technologies, especially at night. However, while it is tempting to make these type of inter-technology comparisons, as Jenkins (1991) cautioned, “The results of these experiments pertain to the particular samples tested, the formats of the symbols and characters used, the mounting assemblies they were in, and the lighting systems that were used for illumination.... The conclusions found should not be generalized to other configurations.” With the technological advancements that have occurred in the past decade, this caveat is even more applicable today.

Light Reflecting

Static-like

This category includes any VMS that is only capable of displaying a set of prefabricated "hard copy" sign messages. These technologies (discussed in detail in Dudek, 1991) represent the oldest VMS technology, but can still be found in use today. They include fold out,rotating scroll, and rotating drum signs. Of these, rotating drum is the only technology that has any current adherents. The rotating drum (or prism) sign has the appearance of a standard or staticsign, however lines of text are mounted on a rotating drum with different messages on each side. When the drum rotates, a new message appears on the sign.

Advantages:

Disadvantages:

Utility in the Transit Environment

This type of VMS has been used extensively in the transit environment in the past, but has fallen out of favor because of the disadvantages listed above, and the availability and increased capabilities of LED and video display unit/cathode ray tube (VDU/CRT) technologies.

Reflective-Disk (RD) Matrix

Also called flip-dot or flip-disk, these signs consist of a matrix of circular,square, or rectangular elements that are reflective on one side and matte black on the other. Electromagnetic current rotates the elements to display either the black or reflective side, with the reflective elements creating the message. The reflective coating can be paint or vinyl, fluorescent or retro reflective. The most common color is yellow, but white and orange can also be found.

During the daytime, sun or ambient lighting illuminates these signs, while under low ambient light conditions they are illuminated by an internal light source. The RD VMS that use retroreflective disks (exclusively for highway use) receive nighttime illumination from vehicle headlamps as do static retroreflective signs. Some also have an internal bank of fluorescent lamps located behind the elements to supplement vehicle headlighting.

The design of RD VMS can be described as module character, continuous line, or full matrix. In a modular character matrix sign, each character is displayed as a discrete unit typically consisting of a matrix of five horizontal and seven vertical elements (i.e., 5x7 charactermatrix). In a continuous line matrix sign, there are no vertical breaks between elements, but there are horizontal breaks between lines of text. An example of this is the standard single-line VMS often found in the transit environment; in highway usage they typically have three lines. In a full matrix sign there are no breaks at all and the sign is one continuous matrix. The latter is the most flexible as it allows for various letter heights, widths, stroke-widths, inter-character and inter-word spacing, and the use of symbols. The former is the most restrictive as it only allows for alphanumerics and significantly restricts letter characteristics (e.g., stroke width, letter width, and letter height).

Advantages

Disadvantages

Utility in the Transit Environment

Earnhart (1996) wrote, “...flip-dot displays are most suitable for on vehicle displays wherespace limitations and cost limitations exist.” Reflective disk VMS have been, and continue to be, used extensively on and within buses. In 1992, Cobern, Martin, Thompson, and Norstrom stated “Flip dot signs have been used on the exterior of buses because of the problems that natural light poses for the other technologies. LED and LCD have proven to be less visible in natural light.”

Light Emitting

Blank Out

These are signs that display a discrete number of “hard wired” messages. They employ a wide variety of technologies including fiber optic, neon, and incandescent or fluorescent bulbs. A typical application of this technology is the “open” or “closed” signs for truck weigh-stations, HOV lanes, and toll plazas.

Advantages

Disadvantages

Utility in the Transit Environment

This technology has only limited utility in the transit environment for the same reason it has limited utility in the highway environment: the lack of flexibility in message display.

Lamp (Bulb) Matrix

These signs are created out of an array of light bulbs that are turned on or off to display the intended message. Like RD VMS, these signs can be modular character, continuous line, or full matrix.

Advantages

Disadvantages

Utility in the Transit Environment

Although popular with the advertising community, very few highway agencies have continued the use of this technology since their peak deployment in the 1970’s. In a survey of 27 states and one Canadian Provence,Dudek (1997) reported that only California had purchased a bulb matrix VMS since 1976. It is unlikely that, given the advances in other light emitting technologies (LED in particular), the advantages found with lamp matrix signs are sufficient to outweigh the disadvantages.

VDU or CRT

Known commonly as television monitors, transportation application of this VMS technology is exclusive to transit, and because of size and glare considerations is restricted to indoor use.

Advantages

Disadvantages

Utility in the Transit Environment

“...VDU displays are more suitable for indoor displays where better control of lighting and more space exist, than at vehicle stops, or onboard vehicles.” (Earnhart, 1996) Because of its display flexibility, this technology has the capability of providing information legible to travelers with vision impairments. Unfortunately the alphanumerics used are typically far too small which, when combined with mounting height, makes their messages difficult even for fully sighted individuals to read.

Liquid Crystal Display (LCD)

The liquid crystals work as a “solid state light shutter” creating an image on the screen by blocking some portions of light and allowing other portions to pass through (Stainforth and Kniveton, 1996). There are three basic types of LCD VMS: reflective; transmissive; and transflective. Reflective LCD VMS have reflective sheeting behind the crystals and use ambient illumination reflected through the crystals to illuminate the sign. Transmissive LCD VMS are illuminated with an internal light source located behind the crystals.Transflective LCD VMS combine the reflective and transmissible properties of the other two (these are addressed in the hybrid VMS section below).

Advantages

Disadvantages

Utility in the Transit Environment

There is some disagreement regarding LCD applicability in the transit environment.Earnhart (1996) stated that they provide, “Good performance in displaying schedule information in transit facilities,” and that, “Mosaic tile TNLCDs present a very readable character, even for those with visual impairments.” He went on to write; “TNLCD displays are most suitable for on vehicle or vehicle stop displays where space limitations, vibration, and the desire for advertising revenue exist.” However, Stainforth and Kniveton (1996) reported poor visibility in general, and legibility in particular, and poor color capability.

Fiber optic (FO) Matrix

FO VMS(also called Light Conductor Technology - Bendekovics and Zelisko, 1996) work by running fiber optic cable from a light source within a sign cabinet to small holes in the sign face. The holes are then alternately blocked or exposed by electromechanical shutter devices. The holes form a matrix in the sign face which, when the light is let through,create the message. As with RD and bulb matrix, the sign can be modular character, continuous line, or full matrix; however in practice they are mainly modular character matrix.

Advantages

Disadvantages

Utility in the Transit Environment

Bendekovics and Zelisko (1996) reported that Austria’s rail network (OeBB) has been using fiber optic VMS for over 20 years, although it is not clear if these were matrix or blank-out signs. Regardless of the specific technology application, however this usage seems to be the exception, for while FO technology has made some market headway in highway VMS, there has not been much interest shown by the transit community.

From a visibility perspective, they are as legible as LED VMS and suffer the same problems with glare in bright daylight. FO VMS, however, have the added potential maintenance problems associated with reflective disk signs (i.e., electromechanical shutters) and bulb matrix VMS (i.e., lamp replacement).

LED Matrix

Modern LED VMS are constructed of a matrix of LEDs, with clusters of LEDs acting as a single element. The number of LEDs per cluster is dependent on sign size. Most transit VMS useeither a single LED per element on signs with three-to-four inch letter heights and four LEDs per element for the larger signs. The illumination of select LEDs creates the message. As with RD, bulb, and fiber optic signs, the LED VMS can be modular character, continuous line, or full matrix.

In the mid to late 1980’s, highway agencies began experimenting with the use of LED VMS with mixed results (Garvey, 1996). However, there have been a number of new advances in LED technology. As recently as the early to mid 1990’s, outdoor LED VMS were limited to the use of the color red, because no other color was bright enough to satisfy daytime transportation needs. Indeed,Wourms, et al. (2001) stated that red is still the only color LED that is capable of producing sufficient light for outdoor daytimeuse, however this is not the case. With the advent of new semiconductor materials such as InGaN in 1993 and even more recently AlInGaP, it is possible to make VMS using essentially any color desired while maintaining high luminance and wide viewing angles (Thomas, 1996; Yoshida, 2000).

The combination of high brightness, multiple colors, long life span (10 years estimated - Swinea, 1999), and lower power consumption that LEDs provide, is why they are used so frequently as replacement technology for red, yellow, and green incandescent traffic signal heads (i.e., traffic lights) and for construction work zone arrow panels, which require a visibility distance of one mile (Lewis, 2000). Research has not been conducted, however, to determine how best to implement this emerging technology to provide optimal VMS readability for individuals with vision impairments.

Advantages

Disadvantages

Utility in the Transit Environment

Iannuzziello’s (2001) reported of a 63 transit agency survey across 29 states and 4 Canadian provinces found LED destination signs to be among communication modes most frequently identified as “very effective.” Earnhart, 1996 wrote, “LED displays are most suitable for on vehicle or vehicle stop displays where space limitations, vibration, and the desire for advertising revenue exist.” Cobern, Martin, Thompson, and Norstrom (1992) wrote “LED and LCD…have more applicability inside the vehicle where they are not subject to direct sunlight.” However, Hunter-Zaworski (1994) reported that France, Sweden, and Canada were using monochromatic and colored LED readerboards for those applications as well as within terminals. The bus stop signs displayed “route, destination, schedule and delay information” while the in-vehicle signs informed passengers of the next stop and any required transfers. Hunter-Zaworski also reported that transit authorities in the Netherlands and England were using LED signs in bus stations to convey real-time bus arrival information. Willis (1995), in reporting the results of a transit agency survey, stated that LED displays were “the most commonly used technology.” This was consistent with her survey of vendors that found LEDs to be the most commonly used technology in bus interiors.

In 1996, Dobies reported that “LED electronic wayside signs mounted above a bus shelter are more visible than most static displays, and messages can be changed much more easily.” He also reported that Denver, CO replaced their RD signs with LED VMS due, at least in part, to maintenance considerations. Those LED signs provided route and gate numbers and scheduled departure time. Denver’s future plans were to link the LED signs with ITS technology to provide real-time departure and arrival times.

Hybrid

The hybrid VMS technologies are basically an attempt to counteract the shortcomings associated with light emitting and light reflecting technologies used alone. Specifically, light emitting technologies suffer under bright ambient conditions where they lose contrast. This results in an effect known as veiling luminance (or glare) in which the message is “washed out.” A severe reduction in contrast creates signs that are unreadable at any letter height. While some light emitting technologies, such as bulb matrix and newer LED signs, can at least partially overcome this problem, the addition of reflective elements can greatly enhance bright daylight VMS visibility. Clean, new, light reflecting technologies work well under bright ambient conditions, but suffer at night. Nighttime lighting of reflective VMS, however, requires lighting the entire sign (both “on” and “off” elements), which reduces contrast. Furthermore, most of the nighttime lighting is either inadequate or has a non-uniform distribution resulting in “hot spots” and “dark spots.” Garvey and Mace (1996) in evaluating the nighttime legibility of VMS found significant reduction in nighttime legibility distance with reflective signs.

Liquid Crystal Transflective

This is a type of LCD that combines the illumination techniques of the reflective and transmissive LCDs discussed earlier. Transflective LCD's are illuminated from the front either by lighting internal to the sign cabinet or by ambient lighting and are also backlit by lights situated in the sign cabinet behind the liquid crystals. These VMS have some of the same disadvantages as the other LCD types, however because they reflect and emit light, they can be used under both indoor and outdoor conditions. As with most of the other technologies, there are no human factors studies evaluating the legibility of transflective LCD for subjects with vision impairments.

FO/RD Matrix

This is a hybrid of reflective disk matrix signs with fiber optics added for nighttime lighting to avoid the problems associated with the external “flood lighting” used with standard RD VMS. By the early 1990's, highway agencies had become disenchanted with the visibility they were able to achieve with traditional RD VMS. At the same time, fiber optics and LEDs were being introduced as stand alone technologies for VMS. A number of agencies had their old RD signs retrofitted with FO/RD components. The principal advantage is uniform lighting across all the characters at night and very good performance in bright daylight as long as the protective “glare screen” is kept clean and scratch free and the elements are not faded. The disadvantages are the same as those reported for the FO and the RD signs (e.g., bulb replacement and moving parts). Applications to the transit environment are the same as with RD VMS.

LED/RD Matrix

This is a hybrid of reflective disk and LED technologies. The rational for this technology is the same as with the FO/RD VMS. The advantages are the same, except that the life of an LED is substantially longer than that of an incandescent lamp, so lamp replacement would not be as much of an issue. A disadvantage is that power consumption is higher in the LED/RD matrix VMS than with either the standard RD or LED VMS because the LEDs are constantly illuminated. Applications to the transit environment are the same as with RD VMS.


CONCLUSIONS, RECOMMENDATIONS, AND FUTURE RESEARCH NEEDS

In 2001 the Public Rights-of-Way Access Advisory Committee made the following statement:

“Research is needed to determine specifications for changeable message signs that will result in equivalent legibility for readers having visual acuities from 20/20 to 20/200, in outdoor situations. Technical specifications are needed for changeable message signs of different types and colors, in situations in which messages are either static or dynamic, and in situations in which either the viewer or the sign are in motion.”

Whether or not the goal of “equivalent” legibility for people with vision impairments can ever be attained is subject to debate, however the present research has identified the existence of certain design criteria that, if met, will be capable of significantly improving the legibility of VMS for a large percentage of individuals with vision impairments. The question is, are the current findings sufficiently robust to be used to make solid recommendations.

In a very recent synthesis on LED/LCD VMS for use on transit vehicles conducted for the FTA, Wourms,et. al. (2001) concluded that there was sufficient available guidance on several indices, including: the position of on-vehicle VMS; character height; width-to-height ratio; stroke width-to-height ratio; and inter-character spacing. Conversely, these researchers stated that there were insufficient data regarding: visibility under varying lighting conditions; streaming and paging style and rate; sign color; relative motion between the sign and the observer; and glare effects.

The present research supports Wourms and his colleagues’ conclusions regarding the need for further research to fill the gaps they identified, particularly with regard to paging and streaming rates and time allotted for individuals with vision impairments to read VMS. The present study however demonstrates that other issues (e.g., letter height, color, and luminance), alone and in combination, may still benefit from additional study.

In particular, appropriate letter heights should be established using new, brighter light emitting VMS, in combination with streaming text for subjects who have a variety of functional visual impairments (e.g., scotoma, CFL, and PFL). The use of an analytical model to determine letter heights (as suggested by Wourms, et al. 2001 and others) simply does not address the complexity of VMS reading by individuals with vision impairments in real-world environments. A summary of recommendations regarding the application of current knowledge to future VMS design and recommendations for future research to fill the gaps in that current knowledge can be found in Table 2.

Table 2.Recommended values for VMS characteristics, issues, and future research needs. (Text Version)

VMS Characteristic Recommended Values Issues and Future Research
Letter Height for VMS on Vehicles Not less than 10 inch

(will allow for 30 ft legibility distance at an LI* of 3 ft/in)
-- Using 8-inch letters, Bentzen, et. al. (1994) found mean VMS legibility distance to be less than 20 feet for subjectswith 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.
Letter Height for VMS in Facilities Not less than 6 inch

(will allow for 18 ft legibility distance at an LI of 3 ft/in)
Width to Height Ratio 0.7 to 1.0 -- Existing research on this variable is fairly strong and, at a minimum, supports the use of 5x7 versus a 4x7 character matrix.
Stroke Width to Height Ratio 0.2 -- Existing research on this variable is fairly strong and supports the useof a 1:5 ratio.
Text Color Green or Yellow -- 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 the visually impaired.
Font 5x7 for Uppercase

7x9 for Lowercase
-- Existing research on this variable is fairly strong.
Luminance Night: 30cd/m2

Day: >1,000cd/m2
-- 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.

-- New European standards currently under development should be tracked to determine measurement methods and recommended levels.
Luminance Contrast (Lt-Lb)/Lb = 8 to 12 -- 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.
Inter character Spacing 25 to 40%

letter height
-- Existing research on this variable is strong.
Inter word spacing 75-100%

letter height
-- Existing research on this variable is strong.
Inter line spacing 50 to 75%

letter height
-- Existing research on this variable is strong.
Case Uppercase or mixed case for single words -- Existing research on this variable is strong; however attaining high-quality lowercase letterforms using a matrix format is difficult. If this cannot be attained, then all uppercase letters is preferable.
Lowercase for longer textual messages
Contrast Orientation Positive -- Existing research on this variable is strong for individuals without vision impairments.

-- Research should be conducted to determine if the findings are the same for individuals with vision impairments.
Sign Width Dynamic text should be capable of displaying 6-7 characters -- 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.
Paging or Streaming Streaming -- Additional research should be conducted.
Static Display Time 10 Seconds -- This is a very weak recommendation and very much in dispute.

-- Additional research must be conducted to determine the appropriate reading time needed for sign comprehension by individuals with vision impairments.
Streaming Rate 2.74 seconds per frame dwell time -- This is a very weak recommendation as it is based on a single research study (Bentzen and Easton, 1996).

-- Additional research must be conducted to determine the appropriate streaming rate individuals with vision impairments.

*LI – Legibility Index (legibility distance in feet per inch of letter height).


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Bentzen, B.L. (In Progress).Accessible pedestrian signals. Draft Report to U.S. Architectural and Transportation Barriers Compliance Board under Contract No.PD-97-0772.

Bentzen, B.L., Crandall, W.F., and Myers, L. (1999). Wayfinding system for transportation services: Remote infrared audible signage for transit stations, surface transit, and intersections.Transportation Research Record.No. 1671, p19-26. National Academy Press, Washington, D.C.

Bentzen, B.L., and Easton, R.D. (1996). Specifications for transit vehicle next stop messages. Final Report to Sunrise Systems, Inc.,Pembroke, MA.

Bentzen, B.L., Easton, R.D., Nolin, T.L., and Mitchell,P.A. (1994).Signage specification for transit vehicles: Human factors research.Prepared for the American Foundation for the Blind. New York, New York.

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Colomb, M. and Hubert, R. (1991).Legibility and contrast requirements of variable-message signs.Transportation Research Record.No. 1318, p137-141. National Academy Press, Washington, D.C.

Colomb, M., Hubert, R., Carta, M., and Dore-Picard. (1991). Variable-message signs: Legibility and recognition of symbols.Proceedings of the Conference Strategic Highway Research Program and Traffic Safety on Two Continents, in Gothenburg, Sweden.p45-62.

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Dudek, C.L. (1997).Changeable message signs.NCHRP Synthesis of Highway Practice 237.National Academy Press, Washington, D.C.

Earnhart, G.A. (1996).Guidelines for transit facility signing and graphics.Transit Cooperative Research Program (TCRP) Report 12. Transportation Research Board, National Research Council, National Academy Press. Washington, D.C.

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APPENDIX A: Annotated Bibliography

TRANSPORTATION RESEARCH:

(Abstracts were excerpted from referenced article or were written by Philip Garvey.)

Bentzen, B.L. (In Progress).Accessible pedestrian signals. Draft Report to U.S. Architectural and Transportation Barriers Compliance Board under Contract No.PD-97-0772.

Abstract:The Transportation Equity Act for the 21st Century - TEA-21, the successor to ISTEA - directs the pedestrian safety considerations, including the installation of audible traffic signals, where appropriate, be included in new transportation plans and projects. The bill was signed into law on June 9, 1998.

Bentzen, B.L., Crandall, W.F., and Myers, L. (1999). Wayfinding system for transportation services: Remote infrared audible signage for transit stations, surface transit, and intersections.Transportation Research Record.No. 1671, p19-26.National Academy Press, Washington, D.C.

Abstract:People who are print-disabled, who are blind, or who have other visual impairments are restricted in their ability to participate in public life because of lack of labels and signs in the environment. Currently, persons with severe visual impairments often require extensive assistance from strangers to travel in unfamiliar areas. Many other types of disabilities can prevent people from reading print. In addition to people who are blind or who have low vision, there are many people with head-injuries, autism, and dyslexia, along with persons who have had a stroke, who are not able to assimilate printed language even though they can see the page. Many people can accept the information through speech--that is, having print read aloud to them. Some human factors evaluations of a signage system specifically developed to aid people who have visual impairments or a print-reading disability gain information that is available to sighted people through print are described in this paper. This remote, infrared audible signage system--Talking Signs--is composed of a small infrared transmitter that emits a repeating voice message over a directional light beam to a handheld receiver carried by a blind pedestrian. The infrared system greatly reduces the need for travelers to remember distances, directions, and turns, thereby enhancing independence and efficiency in travel. Results show that remote infrared audible signage provides effective wayfinding information for using transit stations, surface transit, and intersections, enhancing independent use of public transit by people with visual impairments or cognitive disabilities.

Bentzen, B.L., and Easton, R.D. (1996). Specifications for transit vehicle next stop messages.Final Report to Sunrise Systems, Inc.,Pembroke, MA.

Abstract:This project was undertaken to determine optimum characteristics to promote legibility of LED next stop message signs by persons with varying visual acuities, including persons having no visual impairment as well as persons who are legally blind. (Persons who are legally blind have visual acuities of 20/200 or less, in the better eye, with correction, or visual fields of 20 degrees or less in the better eye.) Characteristics of LED next stop message signs considered were color, font, inter-character spacing, streaming vs. paging, change rate, and separation distance between next stop messages and advertising or public information messages. The project obtained both objective data on legibility of messages displayed as 84 participants were riding buses, and subjective data on legibility of messages displayed to three focus groups seated in a room.

Bentzen, B.L.,Easton, R.D., Nolin, T.L., and Mitchell, P.A. (1994). Signage specification for transit vehicles: Human factors research.Prepared for the American Foundation for the Blind. New York, New York.

Abstract:This research was undertaken to identify characteristics of signs in the mass transportation environment, particularly signs identifying transit vehicles, which promote the greatest legibility for persons with visual impairments. Persons having visual impairments are particularly dependent on mass transportation, as their visual status renders them ineligible for drivers’ licenses. As such, these persons may be likely to be disproportionately represented in transit ridership, as compared to their representation in the general population. It was the function of this research to obtain human performance data regarding factors affecting legibility of transit signs, including print signs and changeable message signs (CMS), for persons having various amounts of vision.

Colomb, M. and Hubert, R. (1991).Legibility and contrast requirements of variable-message signs. Transportation Research Record.No. 1318, p137-141. National Academy Press, Washington, D.C.

Abstract:New technologies such as optic fibers and light-emitting diodes are now used for information matrix signs. A field study was carried out to evaluate the best conditions for the legibility of these signs during the day and at night. For legibility criteria, the contrast between the letters and the sign background is chosen for daylight conditions and the luminance of the letters for night conditions. The performance of some commercially available signs is compared with the study results.

Colomb, M., Hubert, R., Carta, M., and Dore-Picard. (1991). Variable-message signs: Legibility and recognition of symbols.Proceedings of the Conference Strategic Highway Research Program and Traffic Safety on Two Continents, in Gothenburg, Sweden.p45-62.

Abstract:A laboratory study of the understanding of six types of signs was conducted using transparencies produced by the EDGAR graphic software developed for the purpose. The signs were presented to observers for a limited time. The influences of the number of points in the matrix and of the shape of the symbol were investigated. This study raises the problem of specifying matrix symbols. It should be continued in an attempt to arrive at simple recommendations for the main symbols. It would be best to discuss this question at the international, or at the European level, since the symbols on road signs should be the same in all countries.

Crandall, W., Bentzen, B.L., and Myers, L. (1996). Remote infrared signage for people who are blind or print disabled: A surface transit accessibility study. The Smith-Kettlewell Eye Research Institute, San Francisco, CA. Report No. 95-0111, 16p.

Abstract:Remote infrared audible signage provides wayfinding information forboth transit stations and surface transit, thereby enhancing independent use of public transit by persons having visual impairments. The focus of this study is to provide the basis for successful transfer of remote infrared signage technology to widespread use. The study had five goals: Determine whether infrared remote signage enhances accessibility to buses and bus stops by patrons who are blind; determine the optimal configuration for the transmitter units for buses and bus stops; provide transit patrons a direct opportunity to determine the usefulness of infrared remote signage in the context of buses and bus stops; provide information regarding the usefulness of infrared remote signage vs. tactile signs to regulatory agencies, so that resources for accessibility to public accommodations can be wisely spent; and, provide for the publication and distribution of information useful to transit officials aboutthe proper implementation of infrared remote signage technology for buses and bus stops.

Daily, K., McGee, H., and Garvey, P. (2000).Optimizing changeable message sign design and use.Final Report for DTFH61-96-R-00061.U.S. DOT Federal Highway Administration,Washington, D.C.

Abstract: Unlike other traffic control devices, there are no nationally recognized specifications regarding the appearance of Changeable Message Signs (also known as Variable Message Signs). This absence of guidelines has resulted in CMSs that display any number of colors, shapes, sizes, fonts, borders, and spacings, all of which affect the signs’ visibility. The goal of this research was to develop sample specifications that would address these issues by providing guidance that, if followed, will maximize portable CMS visibility while keeping costs down. Because of the inherent variability in portable CMS usage, particularly with regard to travel speed and sight distance, this document refrains from setting fixed requirements for portable CMS visibility, but instead lists and discusses CMS visibility elements. Lookup tables are provided to give users the information required to decide forthemselves what values to use when filling in the blanks in the specifications for their particular application.

Dudek, C.L. (1991).Guidelines on the use of changeable message signs.Final Report - DTFH61-89-R-00053. 269p. U.S. DOT Federal Highway Administration, Washington, D.C.

Abstract:The 1986 FHWA publication "Manual on Real-Time Motorist Information Displays" provides practical guidelines for the development, design, and operation of real-time displays, both visual and auditory. The emphasis in the Manual is on the recommended content of messages to be displayed in various traffic situations; the manner in which messages are to be displayed--format, coding, style, length, load redundancy, and number of repetitions; and where the messages should be placed with respect to the situations they are explaining. This report is intended to provide guidance on 1) selection of the appropriate type of Changeable Message Sign (CMS) display, 2) the design and maintenance of CMSs to improve target value and motorist reception of messages, and 3) pitfalls to be avoided, and it updates information contained in the Manual. The guidelines and updated information are based on research results and on practices being employed by highway agencies in the United States, Canada and Western Europe. CMS technology developments since 1984 are emphasized. Since the use of matrix-type CMSs, particularly light-emitting technologies, has increased in recent years,matrix CMSs have received additional attention in this report. The report concentrates on design issues relative to CMSs with special emphasis on visual aspects, but does not establish specific criteria to determine whether to implement displays. The intent is to address display design issues for diverse systems ranging from highly versatile signing systems integrated with elaborate freeway corridor surveillance and control operations to low cost, less sophisticated surveillance and signing systems intended to alleviate a single specific problem.

Dudek, C.L. (1997).Changeable message signs.NCHRP Synthesis of Highway Practice 237.National Academy Press, Washington, D.C.

Abstract:This synthesis will be of interest to traffic engineers in Federal, state, provincial, and local transportation agencies who are responsible for the design and operation of safe and efficient highway systems. It will also be useful to consulting traffic engineers, sign manufacturers, and vendors in the private sector who assist governmental clients in the application of changeable message sign (CMS) and other intelligent transportation systems (ITS) technology. It is an update of NCHRP Synthesis No. 61 (1979). It describes the various types of permanently mounted CMSs in use in the United States and Canada. This technology, also referred to as "variable message signs" or "motorist information displays", is in widespread use in North America. This report of the Transportation Research Board provides information on the various CMS types in use, their typical characteristics, including the technology types, the character (letters and numbers) types and size, and conspicuity. The synthesis presents a discussion on the types of messages used when there are no incidents. Other aspects, such as procurement, maintainability, and warranties are also discussed.

Earnhart, G.A. (1996).Guidelines for transit facility signing and graphics.Transit Cooperative Research Program (TCRP) Report 12. Transportation Research Board, National Research Council, National Academy Press. Washington, D.C.

Abstract: This report documents and presents the results of a research project to develop a graphics design manual describing the use of signs and symbols which provide for the safe, secure, and efficient movement of passengers to and through transit facilities. During the course of this 18-month project, existing signs and symbols were reviewed worldwide; compliance with ADAAG (Americans with Disabilities Act Accessibility Guidelines) was determined for existing signs; new signs and symbols were developed in five functional categories, namely, Identification, Directional, Processing, Regulatory, and Warning; the key signs were tested by focus groups representing major types of disability, as well as transit users and non-users; a standard design manual of signs and symbols was developed that could be used by transit agencies nationwide; and a plan was developed to achieve maximum dissemination of the guidelines nationwide to transit entities. The project was performed in two phases, with Phase I structured to reviewand document the "state-of-the-practice" of signage in the transit industry. More than thirty properties nationwide, representing a broad cross section of the industrywere surveyed and their signage practices documented. Signage information from both international and domestic transit providers were reviewed, and the information needs of transit users that could be satisfied by signs and symbols were identified. Phase II efforts involved the design of candidate symbols and signs and their evaluation by a broad cross-section of transit riders and non-riders, graphics designers, and transit personnel. The evaluation results were factored into the development of these graphics design guidelines incorporating the best of those signs, symbols and graphics design standards for the transit industry.

Garvey, P.M. and Mace, D.M. (1996).Changeable message sign visibility.Publication No.FHWA-RD-94-077.Federal Highway Administration, Federal Department of Transportation Washington, D.C.

Abstract:This research began with a detailed critical review of the literature to determine the factors that most affect CMS visibility. Those variables determined to have the greatest impact on visibility were selected for a three-level analysis. Level One consisted of a laboratory study using a computer simulation of a CMS. During this stage, 11 variables were assessed regarding their effects on minimum observable letter size. These variables were: character width-to-height ratio (W:H), stroke-width-to-height ratio (SW:H), matrix density, font, color, contrast orientation, character luminance, word-length, inter-word spacing, inter-letter spacing, and inter-line spacing. Level Two was a static field study in which a mock-up CMS, an actual CMS, and the observers were stationary. This second level of analysis measured the effects of time of day, sun position, character height, inter-letter spacing, font, and distance from the observer on minimum character luminance required for CMS legibility. Level Three involved a dynamic field study using actual trailer-mounted CMS's on public roadways. An assessment was made on the effects of seven variables on the distance at which the signs could be found and read. These variables were: sun position, sign type, character luminance, contrast orientation, inter-letter spacing, character height, and character W:H.

Garvey, P.M., Pietrucha, M.T., & Meeker, D. (1997).Effects of font and capitalization on legibility of guide signs. Transportation Research Record, No. 1605, p.73-79. National Academy Press, Washington, D.C.

Abstract: The research objective was to improve highway guide sign legibility by replacing the 40-year-old guide sign font with a new font called Clearview. It was believed that the current guide sign font's thick stroke design, made with high-brightness materials and displayed to older vehicle operators, exhibited a phenomenon known as irradiation or halation. Irradiation becomes a problem if a stroke is so bright that it visually bleeds into the character's open spaces, creating a blobbing effect that reduces legibility. The Clearview font's wider open spaces allow irradiation without decreasing the distance at which the alphabet is legible. Results are presented of two daytime and two nighttime controlled field experiments that exposed 48 older drivers to high-brightness guide signs displaying either the current or the Clearview font. The Clearview font allowed nighttime recognition distances 16% greater than those allowed by the Standard Highway SeriesE(M) font, without increasing overall sign dimensions.

Garvey, P.M., Pietrucha, M.T., & Meeker, D. (1998).Development of a new guide sign alphabet.Ergonomics in Design, 6 (3), p.7-11.

Abstract: To address issues of legibility and visibility of road signs from a distance and at night, a new font, named Clearview, was developed by Meeker & Associates and tested by the Pennsylvania Transportation Institute (PTI) at Pennsylvania State University. After creating initial versions of the fonts, the authors subjected them to an iterative design process based on the results of subjective field evaluations, objective tests of the typefaces'degradability, and objective laboratory studies using computer simulation. The steps in this evaluation process are described here.

Garvey, P.M., Thompson-Kuhn, B. & Pietrucha, M.T. (1995). Sign visibility literature review. United States Sign Council (USSC) Research Project, Final Report.

Abstract:The main objective of this research was to present a synthesized review of literature pertaining to sign visibility. The table of contents lists the following major subject headings. 1. Introduction; 2. Basic Definitions - Lighting, Signs,The Driver; 3. Sign Ordinance Restrictions - Permitted and Prohibited Signs, General Physical Restrictions, Restrictions by Specific Sign Type; 4. Sign Visibility Literature Review - Federal Traffic Sign Regulation, Sign Visibility Research; 5.Understanding Driver Limitations - Visual Acuity, Glare Sensitivity, Reading Time; 6.Sign Visibility and Traffic Safety; Appendix A. Visibility Guidelines for On-Premise Signs; Appendix B. Annotated Bibliography.

Howett G.L. (1983). Size of letters required for visibility as a function of viewing distance and observer visual acuity.National Bureau of Standards. Report No.HS-037 967; NBS TN 1180 Final Report. 72p.

Abstract:A formula is derived giving the letter stroke-width needed for legibility of words on a sign at any given distance by an observer with any given visual acuity. The stroke width, in turn, determines the letter size, depending upon the characteristics of the type face used. The derivation is strictly mathematical and is based on the assumption that beyond a distance of a few meters, a person's visual acuity is specifiable by a fixed visual angle, independent of the distance. The information implicit in the formula is also presented graphically, in four plots that apply to four different combinations of length units for measuring stroke width and viewing distance. Also presented are formulas and graphs for correcting the critical stroke width for nonstandard contrast or background luminance. These correction formulas are based on a body of data on visual acuity as a function of contrast and background luminance, and a formula fitting the mid-ranges of the data, both published recently by other researchers.

Hunter-Zaworski, K. (1994).Accessing public transportation: New Technologies Aid persons with sensory or cognitive disabilities.TR News, 175, p24-29.

Abstract:The Americans with Disabilities Act of 1990 requires that transit systems ensure effective communication with persons with disabilities, including those with sensory and cognitive impairments. The legislation has stimulated the development of a number of new technologies to help those with disabilities access public transportation systems by maximizing the independence and dignity of these passengers. A number of the new and advanced technologies are currently under development, undergoing demonstration, or in early use. When fully implemented, it is anticipated that these innovations will make the transit trip as seamless and pleasant as possible for all travelers, not just for those with disabilities. This article examines some of these new technologies, including the following: For Trip Planning - tactile maps, telecommunication devices for the deaf, hearing aid-compatible telephones, facsimile equipment, "Smart" traveler systems, handyline, and busline; For Getting to and from Transit Facilities - bus stop and transit station access, electronic speech information equipment, auditory pathways, route cards, verbal landmark systems, and talking buses; For Fare Collection - smart cards and the Fahrsmart system (Germany); For Navigating the System - visual signs and electronic information systems (descriptions of systems operating in San Diego, California, St. Saulve, France, Montreal, Quebec, Canada, Rotterdam and Utrecht, Netherlands, and London, England); Technologies Under Development - automatic speech recognition systems, radio frequency fare cards, and GIS (geographic information system) and AVL (automatic vehicle location) technologies; and Future Concepts.

Hunter-Zaworski, K., and Hron, M.L. (1999).Bus accessibility for people with sensory disabilities.Transportation Research Record.No. 1671, p40-47.National Academy Press, Washington, D.C.

Abstract:With the passage of the Americans with Disabilities Act (ADA) it has become a civil rights violation to deny access to public transportation to people with disabilities. The ADA requires transit agencies to provide accessible buses or equivalent services to people with mobility, sensory, or cognitive impairments. Issues concerning people with sensory impairments, and their access to fixed-route transit services, are examined in this study. The literature concerning access to public transit by people with sensory disabilities is summarized in this paper, along with exemplary training programs and technologies that have improved transit accessibility for people with sensory disabilities. A major conclusion of this study is that technological solutions may not increase bus accessibility for people with sensory impairments. One-on-one interaction is needed to solve many individual access problems of the transit users. Training for transit personnel is needed so personnel can become aware of, and more sensitive to, the needs of all transit users. Training for the transit user is necessary so that use of the transit system is accomplished with grace, speed, efficiency, and dignity. Training for those who train people with disabilities is necessary so that transit travelers will be informed about all the available services offered by transit agencies. Visual signage must be consistent and highly legible to be effective and includes sign and information location, lighting, contrast, and content.

Hunter-Zaworski, K.M. and Watts, D. (1994).Development of ergonomic guidelines for electronic customer information systems. Federal Transit Administration Report Number: FTA-OR-26-7000-94-1, 117pp.

Abstract: This study examines issues concerning persons with sensory and cognitive impairments and their access to public transit. The research focuses on the development of ergonomic performance guidelines for visual electronic customer information systems. It is the first attempt to provide direction for the specification and installation of these devices. The guidelines were influenced by the particular needs of persons with sensory or cognitive disabilities. The approach kept the guidelines general to accommodate the particular needs of persons with sensory disabilities in a number of language formats and electronic media. The first part of this report provides a compendium of current state-of-the-art in electronic customer information systems, including a list of model installations and summary descriptions of exemplary and currently operating systems. The second part of the report provides draft guidelines for the ergonomic performance of the man-machine interface of the visualcomponent of electronic customer information systems. The guidelines incorporated the comments and suggestions received from more than 50 reviewers around the world. These reviewers represent transit agencies, groups of persons with disabilities, researchers, manufacturers, and government officials. The final section of this report includes a brief discussion of a number of controversial issues that arose out of the research activities and suggestions for further investigation. It is anticipated that the guidelines will form the basis of international standards to be developed as a cooperative effort between the United States, Canada, Australia, and the European Community as well as the basis for work related to the ITS/APTS program.

Iannuzziello, A.S. (2001) Communicating with persons with disabilities in a multimodal transit environment: A synthesis of transit practice. Transit Cooperative Research Program (TCRP) Synthesis 37. Transportation Research Board, National Research Council, National Academy Press. Washington, D.C.

Abstract: This synthesis will be of interest to transit agency professionals and the consultants who work with them in dealing with travelers with disabilities. These are travelers with sensory, vision, hearing, and cognitive impairments who need alternative methods for accessing and processing the transit information that is now being commonly provided to the general public. The report describes current North American transit practice in information and communication technologies, as well as operations, implementation, and human factor issues. Attention is given to information and communication technologies related to planning, customer service, marketing, and training that can improve the travel experience for all persons traveling in a transit environment. The focus is on the communication techniques and technologies for persons with sensory and cognitive disabilities. This document from the Transportation Research Board integrates information from a literature review, survey responses from 19 transit agencies, and extensive telephone interviews with seven specific providers.

Joffee, E. (1995).Transit vehicle signage for persons who are blind or visually impaired. Journal of Visual Impairment and Blindness, 89(5), Research Notes, p461-469.

Abstract:The purpose of this research project was to identify factors associated with the readability of conventional print and electronic signs used on transit vehicles, specifically buses, in the dynamic transit environment by persons with visual impairments. The subjects were individuals with visual impairments whose visual acuities ranged from 20/70 to 20/400. Conventional and Changeable Message Signs were evaluated.

Klein, R. (1991). Age-related eye disease, visual impairment, and driving in the elderly.Human Factors, 33(5), p521-525.

Abstract:As people age, a number of visual functions such as acuity, visual field, and night vision deteriorate. This decline in vision is associated in part with an increase in vehicular accidents per mile driven by the elderly. Four age-related occular conditions - cataract, macular degeneration, open-angle glaucoma, and diabetic retinopathy - are primarily repsonsible for the decline in visual acuity and visual field in the elderly. Few epidemiologic data are available about these diseases, and at present they cannot be prevented. There is need for more information about visual decline and how it affects driving performance and for development of pragmatic approaches for detecting and assessing the elderly driver with functional visual deficits.

Levinson,M. (1996).Brighter benefits from VMS.Traffic Technology International ‘96.Annual Review Issue, p.201‑2.

Abstract:This article discusses recent experiences of installation of variable message signs (VMSs) in Israel and the Netherlands. Although VMS systems have been used worldwide for more than ten years, they have suffered from display technology limitations and other problems until very recently. Improvements in technology, including the use of light‑emitting diodes (LEDs) have now made the applications of VMS to road traffic beneficial to drivers and government departments responsible for road safety. A pilot project was recently conducted in Haifa, Israel, to evaluate the efficiency of VMS units in an urban area. Four VMS units were tested, each displaying two 24‑character lines of text with 25cm height. Drivers were interviewed while waiting for traffic lights to change at intersections displaying the units. It was found that drivers prefer to have traffic information, even if they do not use it. Most drivers could read the VMSs and think that VMSs reduce traffic anxiety. The Dutch Ministry of Traffic recently began roadside testing of an LED VMS mounted on a mobile trailer. It was found that only 4.4% of cars were speeding past a roadworks sign, displaying very bright yellow‑white LEDs visible in daylight, even in direct sunlight. Thirty-four LED lane control signs have recently been installed in Jerusalem.

Lewis, D.J. (2000).Photometric requirements for arrow panels and portable changeable message signs. Proceedings of the Ninth Maintenance Management Conference, Juneau, Alaska, July 16-20. National Academy Press, Washington, D.C.

Abstract:Arrow panels and portable changeable message signs are often used in work zones to inform drivers of the need for a lane change or caution. The "Manual on Uniform Traffic Control Devices" (MUTCD) requires that Type C arrow panels have a minimum legibility distance of 1.6 km (1 mile). However, the MUTCD does not provide a subjective means for determining whether an arrow panel meets this criterion. Nor are there industry photometric standards for message panels. The purpose of this project is to develop a reliable and repeatable objective method for measuring the photometrics of arrow and message panels to ensure adequate performance. The research project tasks include a review of the state of the art, reviews of existing pertinent specifications, development of initial test methods, evaluations of arrow and message panel visibility and the effectiveness of the test methods, revisions and modifications of the test methods, and documentation of research activities and findings. The research findings will be described in a research report and a project summary report. The recommended test methods will be included in both documents.

Marin-Lamellet, C., Pachiaudi, G., and Le Breton-Gadegbeku, B. (2001).Information and orientation needs of blind and partially sighted people in public transportation.BIOVAM project. Transportation Research Record, No. 1779, 203-208.National Academy Press, Washington, D.C.

Abstract:Presented are the results of the BIOVAM project in France concerning the problems experienced individuals with vision impairments who use public transportation, such as buses, subways, and trains. The project focused on information gathering and orientation processes in the public transportation context. The BIOVAM approach uses a questionnaire survey to identify the main difficulties that public transportation users with visual impairment must manage. The approach includes a review of promising devices that could reduce these difficulties,such as personal information systems and tactile pavements. An overview of the results obtained from the survey is presented, addressing the use of buses and subways. The main technical solutions considered by the project are described, and the research protocols that are to be used in the field experiments are presented. The results of the BIOVAM project could be used to make concrete recommendations to include the specific needs of travelers with visual impairments in the design of a public transport infrastructure.

Marston, P.P. (1993). Changeable message signs: avoiding design and procurement pitfalls.Public Roads, 57(2), p27-34.

Abstract:The use of changeable message signs (CMS), which display real-time information to motorists, has assisted in efforts to improve roadway operations and safety of existing facilities. Some of the difficulties that currently exist with the procurement and implementation of CMS are due to several major issues including inadequate specifications, insufficient definition of protocols, low bid acceptance practices, and no industry standards. This article describes the various CMS technologies and their uses, explains some of the challenges inherent with their use, and recommends solutions to the problems. The key to producing a specification that addresses the needs of the public agency without compromising any one company or technology lies in creating a performance-based specification considering the agency's goals and objectives. Guarantees, warranties, performance/liquidated damages bonds, and independent testing and certification can be successful tools in helping the agency acquire and maintain an efficient and safe CMS network, avoiding the design and procurement pitfalls associated with CMS. The Arizona Department of Transportation provides a good example of the way that a transportation agency can approach CMS.

Miller, J.S., Smith, B.L., Newman, B.R., and Demetsky, M.J. (1995). Final Report: Development of manuals for the effective use of variable message signs. Virginia Department of Transportation, Report No.VTRC 95-R15.

Abstract:A comprehensive research effort to develop operator’s manuals for variable message signs (VMSs) was undertaken to improve the operations of both portable and permanent (fixed-site)VMSs in Virginia. This report describes the development of two manuals, the “Permanent VMS Operator’s Manual” and the “Portable VMS Operator’s Manual.”

Miller, J.S., Smith, B.L., Newman, B.R., and Demetsky, M.J.(1995). Effective use of variable message signs: lessons learned through development of users' manuals.Transportation Research Record, 1495, p1‑8.

Abstract: In an effort to improve the operations of both portable and permanent (fixed‑site) variable message signs (VMSs) in Virginia, a comprehensive research effort to develop operational guidelines was undertaken. These guidelines, presented in the form of users' manuals, were based on information obtained from the literature, VMS operators, and motorists. Issues addressed by the manuals include whether to use a VMS, where to place a portable VMS, and how to design a VMS message. The manuals are not simply a list of predefined messages; instead, they are composed of concise, readable modules designed to guide an operator through the thought process required to use a VMS effectively. An operator follows a logical decision tree as each module is completed, allowing effective use of the VMS as well as training the operator for use of the device. Key lessons learned in developing two such manuals for portable and permanent VMSs are highlighted. On the basis of theoretical calculations and motorists' experiences, it is strongly recommended that a VMS use no more than two message screens. A single message screen is preferred. VMSs should be used only to advise drivers of changed traffic conditions and to convey specific traffic information concisely. Because of limited information capabilities, VMSs should be used in conjunction with other means of communication such as highway advisory radio and static signs. Most importantly, it is crucial that credibility be maintained. Incorrect information can have disastrous consequences on VMS effectiveness.

MUTCD 2000: Manual on Uniform Traffic Control Devices Millennium Edition.(2000).U.S. DOT, Federal Highway Administration. http://mutcd.fhwa.dot.gov/kno-millennium.htm

Abstract:The Manual on Uniform Traffic Control Devices (MUTCD) defines the standards used by road managers nationwide to install and maintain traffic control devices on all streets and highways. The MUTCD is incorporated by reference in 23 Code of Federal Regulations (CFR), Part 655, Subpart F. Although the MUTCD is routinely updated to include amendments that clarify new standards and incorporate technical advances, it has been more than 20 years since the manual was entirely rewritten, and the most recent edition was published in 1988. The new MUTCD is published in 3-ring binders for easy updating, on CD-ROM, and on the Internet. Redesigned text format will help users identify STANDARDS -- "shall" conditions; GUIDANCE -- "should" conditions; OPTIONS -- "may" conditions; and SUPPORT -- descriptive and/or general information for designing, placing, and applying traffic control devices. Measurements are presented in both metric and English units. This hard copy version contains the following sections: Introduction; Part 1 - General; Part 2 - Signs; Part 3 - Markings; Part 4 - Highway Traffic Signals; Part 5 - Traffic Control Devices for Low-Volume Roads; Part 6 - Temporary Traffic Control; Part 7 - Traffic Controls for School Areas; Part 8 - Traffic Controls for Highway-Rail Grade Crossings; Part 9 - Traffic Controls for Bicycle Facilities; Part 10 - Traffic Controls for Highway-Light Rail Transit Grade Crossings; Appendix A1 - Congressional Legislation; and an Index.

Proffitt, D.R., Wade, M.M., and Lynn, C. (1998).Creating effective variable message signs: Human factors issues. Final Contract Report, Proj No. 9816-040-940, VTRC 98-CR31.25p.Virginia Department of Transportation, Richmond, VA.

Abstract:This report addresses the human factors issues related to the reading and comprehension of variable message sign (VMS) messages. A review of the literature was conducted on factors that affect how people read VMSs. Several topics were reviewed. The first topic was literacy. Since reading literacy is not a requirement for obtaining a driver's license, VMS composition should reflect the varied reading competence levels of motorists. It was found that about 25% of Virginians over the age of 16 are weak readers and will likely encounter problems reading VMSs. The second topic addressed how people read. Reading is an interactive process that derives much of its speed and accuracy from implicit knowledge acquired through familiarity. This implies that VMS messages should present familiar, standardized content whenever possible. A review of the literature on warning signs was the third topic. This review found that effective warning signs should have several properties: short, concise messages are both easier to read and more likely to be read; and signal words, such as CAUTION, are not effective. Finally, areas for further research were identified. Symbolic messages and abbreviations are worthy of further investigation as they have the potential for easy recognition, provided they are familiar to motorists and can be accommodated by the VMS. In addition, although the Manual on Uniform Traffic Control Devices (MUTCD) advises angling the VMS away from the roadway to reduce headlight glare, angling the VMS toward the roadway could be desirable for increasing readability. In both these areas, theoretical and practical work is needed. The report recommends that these human factors characteristics and limitations be taken into consideration in the deployment of VMSs and in the composition of their messages.

Public Rights-of-Way Access Advisory Committee. (2001). Final Report: Building a true community. U.S. Architectural and Transportation Barriers Compliance Board. Washington, D.C.

Abstract:Public rights-of-way harbor many transportation activities, including walking and rolling, bicycling, transit, freight movement, and automobile travel. They house the hardware, such as traffic signals and street lights, that supports those activities. In many cases they contain public and private utilities. With so many diverse functions to be supported, the streetscape within the public right-of-way is often created over a period of time by a variety of minds and hands. This report has been prepared to address access to public rights-of-way for people with disabilities. The report is a recommendation for a new national set of guidelines that define the details necessary to make the streetscapes in public rights-of-way accessible to all users. Accessibility is not an afterthought. The design of a coherent corridor of accessible travel should be the starting point for every project in the public right-of-way.

Simon, R.M. (1993). Americans with disabilities act of 1990: Mandate for full accessibility.Transportation Research News, 168, p17-23.

Abstract:The Americans with Disabilities Act of 1990 (ADA), a comprehensive civil rights law that removes barriers to equal opportunity and provides full societal access for all individuals with disabilities, extends the basic framework of Titles II and VI of the Civil Rights Act of 1964 for coverage and enforcement and Section 504 of the Rehabilitation Act of 1973 for a definition of discrimination. For the first time in history, persons with disabilities are guaranteed sweeping protection against discrimination in both public and private services. The ADA has become what no other Federal transportation legislation has ever been: a mandate for full accessibility in the transportation industry. Its accessibility requirements cover all modes of public and private transportation except air travel, which is covered by the Air Carrier Access Act of 1986 and related U.S. Department of Transportation regulations. This systems-change legislation affects Federal highways, transit systems, private transportation providers, rail transportation, airports, and water transportation. This article provides an overview of the transportation provisions of ADA and related regulations and progress made in their implementation. The primary focus is on public transit.

Stainforth, R.W. and Kniveton, P.E. (1996). Display technologies for VMS.Traffic Technology International '96.Annual Review Issue, p.208‑13.

Abstract: Two years after an original review of display technologies for variable message signs (VMSs), the authors of this article reconsider the new technologies for collective driver information, and argue that improved light‑emitting diodes (LEDs) could become the dominant and cost‑effective light source. The following VMS technologies are compared: (1) rotating planks and prisms; (2) roller blinds; (3) electromagnetic reflecting flip disk; (4) lamp matrices; (5)fibre optics; (6) LEDs; and (7) liquid crystal displays (LCD). Fibre optic signs and LEDs perform best. Fibre optic displays have excellent visibility in all weather conditions, although they can be difficult to read in direct sunlight. The fibre optic reflective disk combines the qualities of fibre optics and the reflective disk to be exceptionally visible in direct sunlight. The advantages and disadvantages of first‑generation technology are listed. R‑R Industrial Controls has developed a new generation of LEDs for transport and traffic applications. Its high intensity yellow LED, Rigel, has greatly increased optical efficiency and reduced power consumption. Its technology has been chosen for several British VMS projects.

Swinea, J.D. (1998).Secrets of selection.Traffic Technology International, Annual Review, p163-165.

Abstract:This article presents criteria that should be considered in selecting variable message sign (VMS) systems. It discusses types and sizes of displays, reliability, software, and service considerations. It also offers general criteria for selecting a VMS company.

Upchurch, J. Armstrong, J.D., Baaj, M.H., and Thomas, G.B. (1992). Evaluation of variable message signs: Target value, legibility, and viewing comfort.Transportation Research Record. No. 1376, p. 35-44. National Academy Press, Washington, D.C.

Abstract:Three different technologies for variable message signs were evaluated in terms of target value, legibility distance, and viewing comfort. The technologies evaluated were flip disk, light-emitting diode (LED), and fiber optic. For comparison purposes, conventional overhead guide signs were also evaluated. Twelve signs were evaluated in the field in a human factors study; hired observers measured target value and legibility distance from a moving vehicle on the freeway and subjectively evaluated viewing comfort. Observations were madeunder four lighting conditions: midday, night, washout, and backlight. For target value, legibility distance, and viewing comfort, fiber-optic signs performed better than LED signs in most conditions. However, both types have acceptable performance overall. The effects of observer age were identified and documented. Both fiber-optic and LED signs are recommended as acceptable for the freeway management system in the Phoenix, Arizona, urban area.

Uslan, M.M., Peck, A.F., and Waddel, W. (1988). Audible traffic signals: How useful are they?ITE Journal, 58(9). p43.

Abstract:This is a report of a controlled study of 27 blind persons who attempted to cross three intersections outfitted with audible pedestrian signals and one without. The legally blind persons were selected to provide a range of visual impairment, type of mobility aid, and age. Details of the method used are described. Details are given of the four study intersections that represented differing degrees of complexity and a variety of challenges to pedestrians with vision impairments. The results of the study are presented and discussed. The study found that audible signals aid blind pedestrians at complex intersections, but also pointed out the limitations associated with audible signals. It is noted that blind pedestrians have difficulty locating the proper pedestrian signal pole and push button. At complex intersections, audible signals require intensified listening, and the full advantage of audible signals can only be realized through instruction and practice in their use.

Wourms, D.F., Cunningham, P.H., Self, D.A., and Johnson, S.J. (2001). Bus signage guidelines for persons with visual impairments: electronic signs. Federal Transit Administration Report FTA-VA-26-7026-02.1.

Abstract:This report focuses on the adequacy of the ADA destination signage guidelines for visual technologies used to improve the dissemination of public transit information individuals with vision impairments. Specifically, this document is concerned with the use of LED and LCD signs in and on the transit vehicle to present destination and route information. The content is derived from relevant standards, guidelines, and research literature identified during extensive government and commercial database searches, as well as a comprehensive search ofworld wide web resources. To the extent available, input from subject-matter experts and industry points-of-contact is also included.

The objective of this on-going research is to update the FTA bus signage guidelines for reflective disk changeable message signs (CMS) (FTA-MD-26-0001-98-1) to include light-emitting CMS technologies (LED and LCD). In task 1 the researchers conducted a literature and document review to identify current CMS guidelines and research related to bus signage for individuals with vision impairments. In task 2 the researchers conducted two user surveys, one with transit authorities and one with users of transit systems with vision impairments. The preliminary results of the transit authority survey indicated that most authorities used ADA regulations as a minimum starting point, but specified larger letter heights. In general, the specifications that the authorities are using are broad-based and often lack specific target values for sign characteristics. The preliminary results from the survey of transit users with visionimpairments indicate that the major problems these individuals have with external bus CMS are: bright daylight (glare); poor use of color; and vehicle motion (vibration). Problems they have with internal bus CMS are: bright daylight (glare); letters that are too small; and text scrolling speed that is too fast. Task 3 will result in a research plan based on the findings of the first two tasks that will be using to determine guidelines to optimize the visibility of light emitting CMS for travelers with vision impairments.

READING WITH VISUAL IMPAIRMENTS:

(Abstracts are from PsycINFO database record.)

Bowers, A.R. and Reid, V.M. (1997). Eye movement and reading with simulated visual impairment. Ophthalmology and Physiological Optics, 17(5), p492-402.

Abstract:Investigated the effects of simulated visual impairment on the reading speed and reading eye movements of young, normally-sighted observers (18-35 yrs old). Afocal diffusing filters (Ryser occlusion foils) were used to create 3 levels of impairment and eye movements were recorded using a spectacle-mounted, infra-red limbal reflection system. Reading speed decreased significantly as the level of impairment increased. Eye movement analysis revealed the main contributory factors to be increased fixation durations shorter saccades (resulting in increased numbers of forward saccades per line) and, to a lesser extent, increased time required for page navigation. The results suggest that in order to achieve optimal reading speeds, print size should be at least 4 times the acuity threshold and that print contrast should be at least 20 times contrast threshold.

Fine, E.M. and Peli, E. (1996). Visually impaired observers require a larger window than normally sighted observers to read from a scroll display. Journal of the American Optometric Association, 67(7), p390-396.

Abstract:Examined the optimal window size for proportionally spaced fonts when reading from a scroll display. Twenty-four visually impaired and 44 normally sighted subjects aged 50+ years were asked to read either sentences or random words scrolled across a computer screen. The window size was varied sothat from 1-12 characters were visible, on average, at any one time. Each subject read with 6 different window sizes within the range of 1-12 characters visible. Results showed that for the normally sighted group, a window of 4-5 characters was necessary to read at maximal rates. Subjects with vision impairments required a significantly larger window of 6-7 characters to reach maximal reading rates. The larger window size requirement for subject with vision impairments could result from the additional stimulation available with a larger window to entrain the eyes' motion when reading from a passively scrolled display.

Fine, E.M. (1995). Reading dynamically displayed text with visual impairments. Dissertations Abstracts International: Section B: The Sciences and Engineering Vol. 56(6B).

Abstract:With normal vision, about 20% of reading time is consumed by eye movements.(Rayner, 1978; Just & Carpenter, 1980). RSVP and scrolled text display formats both require eye movements different from normal reading, and were previously shown to increase reading rates for observers with vision impairments. Because eye movements are either reduced (central field loss--CFL) or eliminated (no CFL and normal vision) when reading from an RSVP display, reading should be faster than when reading from a scroll display. As expected, normally sighted observers read faster from the RSVP display. Readers with vision impairments did not. The remaining experiments explored this unexpected finding. Experiment 2 used a comparison of the ratio of reading rates for sentences and random word strings (sentence-gain) across the display formats to determine if readers use information available from the word to the right of their current fixation. If they do, sentence-gain will be different when reading from the two displays. Normally sighted readers showed less sentence-gain when reading from the scroll display, suggesting they use the available extra-fixational information. Persons with CFL did not. Experiment 3 (young subjects) and Experiment 4 (older subjects) used cataract simulating lenses, and showed that severely reduced acuity does not eliminate the benefit of the single locus presentation of the RSVP display. As with the subjects in Experiment 2, it does eliminate the use of extra-fixational information in the scroll display. In the presence of CFL, reading behavior differs substantially from that of observers with no CFL, regardless of acuity. The fact that these subjects derive no benefit from the reduced eye movement requirements of the RSVP display lends support to the belief that the scroll display entrains their otherwise unstable eye movements (Whittaker et al., 1993; Legge et al., 1985a), thus providing a more visible image. The number of characters usable during a fixation is smaller.

Fine, E.M., Peli, E., and Reeves, A. (1995). Simulated cataract does not reduce the benefit of RSVP.Vision Research, 37(18), p2639-2647.

Abstract:Thirteen younger and 12 older (mean age 71 years) normally sighted subjects read sentences and random lists of words from a rapid serial visual presentation (RSVP) display and a scroll display using their normal vision and through two levels of cataract simulators. Unlike subjects with central field loss, there was no decrease in the benefit of RSVP with reduced vision due to the cataract simulators. However, the usefulness of sentence-level context was reduced as visual acuity was reduced. In addition, older readers did not benefit as much from RSVP as youngerreaders, and many in the older group were unable to read using the more severe cataract simulators from either display format. The data indicate that the benefits of RSVP are not reduced with reduced acuity and contrast sensitivity, and that there are age-related changes in reading rates from dynamic text displays not related to acuity.

Kang, T.J. and Muter, P. (1989). Reading dynamically displayed text. Behaviour and Information Technology 8(1), p33-42.

Abstract: Two experiments with 48 college students were carried out to find an optimal electronic text display method given limited space. The display formats tested were in 2 categories: times square (TS), in which text is scrolled from right to left; and rapid, serial, visual presentation (RSVP), in which text is presented one or several words at a time to a fixed location in the display. In Experiment 1, a comparison was made between multiple-word RSVP and 3 versions of the TS format, differing in the size of steps by which the display was scrolled. Except for the largest step-size, comprehension was as high in the TS conditions as in the RSVP condition. Subjects expressed a significant preference for smooth-scrolling TS over any other condition. Experiment 2 showed that comprehension for smooth scrolling TS was at least as high as that for RSVP at presentation rates ranging from 100 to 300 words/min. TS reading is discussed in terms of optokinetic nystagmus.

Krischer,C.C. and Meisser, R. (1983).Reading speed under real and simulated visual impairment.Journal of Visual Impairment and Blindness 77(8), p386-388.

Abstract:Simulated 2 types of visual impairment--cataracts and deteriorated retinas--in normally sighted subjects (aged 20-45 yrs) with average reading speeds. Three groups of partially sighted persons (N = 72; average age 28 yrs) were also studied: those with normal visual fields, those with defects in peripheral fields, and those with defects in the central field. Results for these 3 groups were similar to those obtained under conditions of simulated visual impairment. The authors conclude that reading speed depends on visual acuity.

Legge, G.E., Ahn, S.J., Klitz, T.S., and Luebker, A. (1997).Psychophysics in reading - XVI.The visual span in normal and low vision.Vision Research, 37, p1999-2010.

Abstract: The visual span in reading is the number of characters that can be recognized at a glance. The shrinking visual span hypothesis attributes reading speed deficits in low vision, and slow reading in normal vision at low contrast, to a reduction in the visual span. This hypothesis predicts that reading time (msec/word) becomes increasingly dependent on word length as text contrast decreases. We tested and confirmed this prediction using the rapid serial visual presentation (RSVP) method. Estimates of the visual span ranged from about 10 characters for high-contrast text to less than two characters for low-contrast text. Eye movement recordings showed that longer reading times at low contrast are partitioned about equally between prolonged fixation times and an increased number of saccades (presumably related to a reduced visual span). RSVP measurements for six out of seven low-vision subjects revealed a strong dependence of reading tome on word length, as expected from reduced visual spans.

Legge,G.E. and Rubin, G.S. (1986).Psychophysics of reading. IV. Wavelength effects in normal and low vision.Journal of the Optical Society of America A 3(1), p40-51.

Abstract: Examined whether color of text influenced its legibility, using psychophysical methods to measure the effects of wavelength on the reading performance of 4 normal observers, 2 dichromats, and 25 low-vision observers (aged 21-71 yrs). Reading rates were measured for text scanned across the face of a TV monitor. Performance was compared under 4 luminance-matched conditions in which sets of neutral-density and Wratten color filters were placed in front of the TV screen--blue, green, red, and gray. Under photopic conditions, the reading rates of normal subjects were independent of wavelength, with the exception of characters near the acuity limit. At lower luminances, wavelength effects could be explained by the shift from photopic to scotopic vision. It was hypothesized that light scatter or absorption in eyes with cloudy ocular media would result in depressed performance in the blue. Only 1 of 7 subjects demonstrated this effect, which was traced to wavelength-specific absorption. Subjects with advanced photoreceptor disorders tended to read blue text faster than red text. It is suggested that wavelength only occasionally plays a significant role in reading. When it does, performance tends to be depressed either in the red or the blue and to be nearly optimal for green or gray.

Lovie-Kitchin, J.E., Bowers, A.R., and Woods, R.L. (2000).Oral and silent reading performance with macular degeneration.Ophthalmology and Physiological Optics, 20(5), p360-370.

Abstract: Investigated whether reading rate for large print sizes shown to be a predictor of oral reading rate with low vision devices (LVDs), would apply using large print sizes more readily available in clinical situations (e.g. 2 degrees, 1.4 logMAR character size) for subjects with macular degeneration. For 22 14.3-88.4 year olds with either juvenile (mean age 36 yrs) or age-related (mean age 76 yrs) macular degeneration, the authors assessed rauding rates (reading for understanding). A combination of near-word visual acuity and large-print reading rate (without LVDs) provided the best prediction of oral rauding rates (with LVDs). However, near-word visual acuity alone was almost as good. Similarly, silent rauding rate was predicted best by near-word visual acuity alone. Near visual acuity limits are suggested as a clinical guide to expected oral and silent reading performance with LVDs for patients with macular degeneration.

Raasch,T.W. and Rubin, G.S. (1993).Reading with low vision.Journal of the American Optometric Association, 64(1), p15-18.

Abstract: Most subjects with low vision express a desire to read standard print as easily and as quickly as possible. There are a multitude of visual factors that can interfere with reading, yet we hove only an incomplete understanding of these factors. These include the relationship between acuity, magnification, and reading performance, the role of eye movements in low vision reading, and the effect of central scotomas on reading performance. We describe current research in each of these areas, and discuss their potential clinical implications.

Yager, D., Aquilante, K., and Plass, R. (1998). High and low luminance letters, acuity reserve, and font effects on reading speed.Vision Research, 38, p2527-2531. Abstract: Compared reading speed in 46 normally sighted high school and optometry students with two fonts, Dutch (serif) and Swiss (sans serif). Text was displayed on a computer monitor, white letters on black, with the RSVP method. Luminance of the letters was either 146.0 or 0.146 cdm2. Lower-case x-height of the fonts was approximately 5.5 times as large as letter acuity. At the high luminance, there was no difference between reading rates. There was a significant advantage for the Swiss font at the low luminance. The acuity reserve for Swiss was higher than for Dutch at the low luminance, which may account for the difference in reading speeds.


APPENDIX B: VMS GUIDELINES,STANDARDS, AND SPECIFICATIONS

MUTCD 2000: Manual on Uniform Traffic Control Devices Millennium Edition. (2000). U.S. DOT Federal Highway Administration.

The following sections were excerpted from the electronic version of the MUTCD Millennium Edition, which can be found at the Federal Highway Administration’s web site at http://mutcd.fhwa.dot.gov/. With the exception of formatting and some minor additions (in italics), nothing was changed.

MUTCD Definition of Changeable Message Signs — signs that are capable of displaying more than one message, changeable manually, by remote control, or by automatic control. These signs are referred to as Dynamic Message Signs in the National Intelligent Transportation Systems (ITS) Architecture.

The MUTCD has general guidance for changeable (or dynamic) message signs which is found in Section 2A.07 and 6F.52. The FHWA has approved experimentation projects to study the operational and safety affects of certain dynamic message signs. For example, approval has been given to Maine DOT to experiment with a dynamic message sign under experimental request no. II-409 (Ex) and approval was also given to Virginia DOT under experimental request no. II-261 (Ex) to evaluate an Intersection Collision Countermeasure System that incorporates dynamic message signs. Our goal is to gather enough evaluation data to help determine future dynamic message sign standards for the MUTCD.

Section 2A.07 Changeable Message Signs

Standard: Changeable message signs, which are traffic control devices designed to display variable messages, shall conform to the principles established in this Manual, and to the extent practical, with the design and applications prescribed in Sections 6F.52 and 6F.55.

Guidance: Changeable message signs should not be used to display information other than regulatory, warning, and guidance information related to traffic control.

Support: Changeable message signs, with more sophisticated technologies, are gaining widespread use to inform road users of variable situations, particularly along congested traffic corridors. Highway and transportation organizations are encouraged to develop and experiment (see Section 1A.10) with changeable message signs and to carefully evaluate such installations so that additional standards may be adopted in the future. Information regarding the design and application of portable changeable message signs in temporary traffic control zones is contained in Section 6F.52.

Section 6F.52 Portable Changeable Message Signs

Standard:Portable Changeable Message signs shall be temporary traffic control devices with the flexibility to display a variety of messages. Each message shall consist of either one or two phases. Typically, a phase shall consist of up to three lines of eight characters per line.

Support: Portable Changeable Message signs are used most frequently on high-density urban freeways, but have applications on all types of highways where highway alignment, road user routing problems, or other pertinent conditions require advance warning and information.

Guidance: The components of a Portable Changeable Message sign should include: a message sign panel, control systems, a power source, and mounting and transporting equipment.  Portable Changeable Message signs should subscribe to the principles established in this Manual and, to the extent practical, with the design (that is, color, letter size and shape, and borders) and applications prescribed in this Manual, except that the reverse colors for the letters and the background are considered acceptable. The front face of the sign should be covered with a protective material. The color of the elements should be yellow or orange on a black background. 

Option: The message sign panel may vary in size.

Standard: Portable Changeable Message signs shall automatically adjust their brightness under varying light conditions, to maintain legibility. The control system shall include a display screen upon which messages can be reviewed before being displayed on the message sign. The control system shall be capable of maintaining memory when power is unavailable. Portable Changeable Message signs shall be equipped with a power source and a battery back-up to provide continuous operation when failure of the primary power source occurs. The mounting of Portable Changeable Message signs shall be such that the bottom of the message sign panel shall be a minimum of 2.1 m (7 ft) above the roadway when it is in the operating mode. The text of the messages shall not scroll or travel horizontally or vertically across the face of the sign.

Support: Portable Changeable Message signs have a wide variety of applications in temporary traffic control zones including: roadway, lane, or ramp closures, crash or emergency incident management, width restriction information, speed reductions, advisories on work scheduling, road user management and diversion, warning of adverse conditions, and operation control.

Guidance: Portable Changeable Message signs should be used as a supplement to and not as a substitute for conventional signs and pavement markings.

Support: The primary purpose of Portable Changeable Message signs in temporary traffic control zones is to advise the road user of unexpected situations. Some typical applications include the following:

  1. Where the speed of motor vehicle traffic is expected to drop substantially;
  2. Where significant queuing and delays are expected;
  3. Where adverse environmental conditions are present;
  4. Where there are changes in alignment or surface conditions;
  5. Where advance notice of ramp, lane, or roadway closures is needed;
  6. Where crash or incident management is needed; and/or
  7. Where changes in the road user pattern occur.

Guidance: When Portable Changeable Message signs are used for route diversion, they should be placed far enough in advance of the diversion to allow road users ample opportunity to exit the affected highway. The Portable Changeable Message signs should be sited and aligned to ensure legibility. Multiple Portable Changeable Message signs should be placed on the same side of the roadway, separated from each other at distances based on Table 6C-1. Portable Changeable Message signs should be placed on the shoulder of the roadway or, if practical, further from the traveled lane. They should be delineated with retroreflective temporary traffic control devices or when within the clear zone, shielded with a barrier or crash cushion. When Portable Changeable Message signs are not being used, they should be removed; if not removed, they should be shielded; or if the previous two options are not feasible, they should be delineated with retroreflective temporary traffic control devices. Portable Changeable Message sign trailers should be delineated on a permanent basis by affixing retroreflective material, known as conspicuity material, in a continuous line on the face of the trailer as seen by oncoming road users.

Messages should be designed taking into account the following factors:

  1. Each phase should convey a single thought.
  2. If the message can be displayed in one phase, the top line should present the problem, the centerline should present the location or distance ahead, and the bottom line should present the recommended driver action.
  3. The message should be as brief as possible.
  4. When a message is longer than two phases, additional Portable Changeable Message signs should be used.
  5. When abbreviations are used, they should be easily understood (see Section 1A.14).

Section 1A.14 Abbreviations Used on Traffic Control Devices (including VMS)

Standard: When abbreviations are needed for traffic control devices, the abbreviations shown in Table 1A-1 shall be used.

Guidance:The abbreviations for the words listed in Table 1A-2 should not be used in connection with traffic control devices unless the prompt word shown in Table 1A-2 either precedes or follows the abbreviation.

Standard: The abbreviations shown in Table 1A-3 shall not be used in connection with traffic control device because of their potential to be misinterpreted by road users.

Table 1A-1. Acceptable Abbreviations

Word Message:  Standard Abbreviation

Table 1A-2. Abbreviations That Are Acceptable Only with a Prompt Word

Word Message Word/ Abbreviation/ Prompt Word

*These prompt words should precede the abbreviation

Table 1A-3.Unacceptable Abbreviations

Abbreviation/ Intended Word/ Common Misinterpretations

The following are from the ADA Accessibility Guidelines for Transportation Vehicles and ADA Standards for Accessible Design. These standards do not directly address VMS or electronic signs in general, but are applied to all signage applications (including VMS) in and on transportation vehicles and in public and commercial facilities. Sections were omitted that did not pertain to sign visibility.

AmericansWith Disabilities Act (ADA) Accessibility Guidelines for Transportation Vehicles Part, 1192

§1192.39 Destination and route signs.

(a) Where destination or route information is displayed on the exterior of a vehicle, each vehicle shall have illuminated signs on the front and boarding side of the vehicle.

(b) Characters on signs required by paragraph (a) of this section shall have a width-to-height ratio between 3:5 and 1:1 and a stroke width-to-height ratio between 1:5 and 1:10, with a minimum character height (using an upper case "X") of 1 inch for signs on the boarding side and a minimum character height of 2 inches for front "headsigns", with "wide" spacing (generally, the space between letters shall be 1/16 the height of upper case letters), and shall contrast with the background, either dark-on-light or light-on-dark.

Nondiscrimination on the basis of disability by public accommodations and in commercial facilities (1994). ADA Standards for Accessible Design.Pt. 36 Department of Justice 28 CFR Part 36.

4.30 Signage.

4.30.2 Character Proportion. Letters and numbers on signs shall have a width-to-height ratio between 3:5 and 1:1 and a stroke-width-to- height ratio between 1:5 and 1:10.

4.30.3 Character Height. Characters and numbers on signs shall be sized according to the viewing distance from which they are to be read. The minimum height is measured using an upper case X. Lower case characters are permitted. Minimum character height 3 in (75 mm). 

Characters and symbols shall contrast with their background --either light characters on a dark background or dark characters on a light background.

The following guidelines and standards are appended from: Wourms, Cunningham, Self, and Johnson, 2001. Bus signage guidelines for persons with visual impairments: electronic signs. Federal Transit Administration Report FTA-VA-26-7026-02.1.

American Public Transit Association (APTA) Guidelines

The Standard Bus Procurement Guidelines (SBPG) issued by APTA are a model for solicitation of offers and contracts for the supply of transit buses. They are intended to be a starting point for a transit agency assembling a solicitation of offers and to assist in a cost-effective procurement. SBPG Part 5: Technical Specifications defines requirements for a heavy duty transit bus which, by the selection of specifically identified alternative configurations, may be used for both suburban express service and general service on urban arterial streets. It is intended for the widest possible spectrum of passengers, including children, adults, the elderly, and persons with disabilities. The destination sign design guidelines offered within Part 5 of the SBPG document are as follows (emphasis added):

I. An automatic electronic destination sign system shall be furnished on the front, on the right side near the front door, and on the rear of the vehicle. Display areas of destination signs shall be clearly visible in direct sunlight and/or at night. The sign system shall provide optimum visibility of the message display units for passengers and shall meet applicable ADA requirements defined in 49 CFR, Part 38.39.

II.The front destination sign shall have no less than 1,689 octagonal dot pixels, 16 rows by 105 columns, with a message display area of not less than 9.8 inches high by not less than 63 inches wide.

III.The side destination sign shall have no less than 672 octagonal dot pixels, having at least 8 rows and 84 columns with a message display area of not less than 3.15 inches high by not less than 30 inches wide.

IV.The rear route number sign display area shall have no less than 448 octagonal dot pixels, having at least 8 rows and 28 columns with a message display area of not less than 6.1 inches high by not less than 11 inches wide.

V. Sign displays shall have alternating message capability with programmable blanking time between message lines as may be required. Variable blanking times shall be programmable between 0.5 to 25 seconds in duration.

Transportation Research Board, Transit Cooperative Research Program (TCRP)

The TCRP, proposed by the U. S. Department of Transportation (DOT), authorized as part of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), and established under FTA sponsorship in July 1992, serves as one of the principal means by which the transit industry can develop innovative near-term solutions to meet the demands of upgrading transit systems, expanding service areas, increasing service frequency, and improving transit system efficiency.

The TCRP provides a forum where transit agencies can cooperatively address common operational problems and support and complement other ongoing transit research and training programs. The next sections provide excerpts from two TCRP reports containing relevant transit signage guidelines and recommendations.

Guidelines for Transit Facility Signing and Graphics—TCRP Report 12

This report was designed to assist transit operators in the use of appropriate signs and symbols for their facilities. These guidelines describe the use of signs and symbols that provide for the safe and efficient movement of passengers to and through transit facilities. These guidelines also assist transit operators in providing passenger information systems that encourage the use of transit by new users, infrequent riders, and individuals with disabilities.

While not specific to destination signage, a section of the report devoted to electronic visual information displays describes the characteristics of LED displays (LED size, dot pitch, character formation, and display luminance) that affect their performance as follows (emphasis added):

I.LED Size—The diameter (or width if the display is a matrix of square LED elements) of one LED is referred to as the "dot size" of the display. The prevalent dot size for transit system displays is currently 5 mm (0.197 in.).

II.Dot Pitch—The dot pitch, or distance between dot centers, which is currently prevalent in transit system displays is 6 mm (.236 in.). Greater spacing between dots produces a reduction in readability. This is due to the loss of a cumulative effect whereby adjacent LEDs act together to form an image, rather than as individual dots.

III.Character Formation—To form a character, a minimum dot matrix of 7 x 9 is preferred. Characters must be double stroke (made up of two adjacent rows of dots).

Display Luminance—The display must be capable of enough brightness to be visible in the intended environment. If lighting conditions are variable, this would make the display too bright for the lower illumination levels. Therefore, dimming controls or sensors should be used for displays with varied ambient conditions. Current indoor, semi-outdoor, and ultra bright versions of LED blocks for different illumination levels are available.

Passenger Information Services: A Guidebook for Transit Systems—TCRP Report 45

The objective of this report is to produce a clear and practical guidebook to assist transit professionals in making transit information more accessible and user friendly for transit systems of varying complexity. The guidelines include a compilation of principles for the design and format details that are part of all passenger information aids. This research did not develop a high-technology, paperless approach to passenger information. Rather, it focused on traditional media for presentation of information, such as schedules, maps, and signage. Therefore, this section first offers recommendations specific to traditional bus header/identifications signs. It then presents general recommendations and guidelines to help make transit information systems easier to read and understand.

I.A bus header/identification sign is mounted on the bus front (at least; rear and sides if possible) in static or electronic form, to identify the route number and name (if any) and, if applicable, the direction in which the bus is traveling. The sign should be visible to passengers waiting at the bus stop.

II.Route number must be legible to persons with low vision (20/200), in daylight conditions, at 30 feet (i.e., six inch high characters and/or symbols, preferably larger).

III.Placementshould be high on the bus body, above the window line.

IV.Display may be by changeable message sign. Back illumination or flood illumination should be provided for nighttime operations.

For general application to transit industry information systems, the following suggestions apply:

I.Use all capital letters (upper case)for stop designations, terminals, and other short labels.

II.Usecapital and lower case letters for long legends and instructions.

Given that viewing distances for signs will vary according to where they are placed in relation to the intended reader, this guidebook specifies most sign character sizes in terms of visual angle. This is expressed either in degrees or in radians. The visual angle is the angle that the letter or other object makes up in the visual field of the reader. A person with “normal” vision (20/20) will just be able to make out letters that are 1/12 degrees(0.00145 radian) of arc. ADA requirements call for the major route designators and other essential information to be visible from 30 feet away by individuals with low vision. This translates into a requirement for approximately 1 degree letters(0.017 radian

For signs and printed materials that are not black-on-white (especially for bus stop signs, which may be a unique color for visibility against other street signs), a contrast formula can help determine how well text or other elements will stand out against a background. Contrast for all signs, schedules, and publications should be at least 70 percent.

The Public Service Vehicle Accessibility Regulations 2000

This United Kingdom document is intended to provide guidance for those in the manufacturing and operating industries. The Public Service Vehicles Accessibility Regulations 2000 prescribe the minimum acceptable to meet the needs of people with disabilities. The guidance explains the intention of the regulatory requirements and provides advice on best practice that should be followed, recognizing that there may be circumstances in which design or operational constraints apply.

A regulated public service vehicle shall be fitted with a route number display and a destination display in the following positions:

I. On the front of the vehicle, as close as practicable to the part of the windscreen which is within the driver’s field of vision; and

II.On the near-side of the vehicle adjacent to the entrance which is closest to the front of the vehicle at a height of not less than 1.2 meters to the lower edge of the display characters and not more than 2.5 meters to the upper edge of the display characters measured from the ground and, if fitted with a kneeling system, with the vehicle in the normal condition for vehicle travel.

III.The front display may be fitted above the windscreen or, as low as practicable within the windscreen area, but above the driver's field of view. It must not be placed in any position that may obscure the driver's field of view.

IV.A regulated public service vehicle shall be fitted with a route number display on the rear of the vehicle.

Any route number display shall be capable of displaying the following:

I. Characters of not less than 200mm in height on the front and rear of the vehicle and not less than 70mm in height on the side of the vehicle,

II.Characters that contrast with the display background,

III.Characters that are provided with a means of illumination, and

IV.Not less than three characters.

Any destination display shall be capable of displaying the following:

I.Characters of not less than 125mm in height when fitted to the front of a vehicle and not less than 70mm in height when fitted to the side of a vehicle,

II.Characters that contrast with the display background,

III.Characters that are provided with a means of illumination,

IV.Not less than fifteen characters, and

V.White or bright yellow lettering on a black background is most clearly visible.

VI.LED/LCD or other electronically generated characters should only be used if they can offer the same clarity, both night and day, as a conventional roller blind display.

VII. Destination information shall not be written in capital letters only. The use of both upper and lower case text helps ensure that words that are not completely clear and legible to people with a degree of vision impairment or learning disability, are still identifiable through shape recognition of the word.