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

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)

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

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.

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

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