There are an estimated 3.7 million people in the United States who are visually disabled, that is, who have corrected visual acuity no better than 20/70¹ in the better eye or who have a maximum visual field of no more than 30 degrees (Genensky, 1994). About 200,000 of these people are blind (have no useful pattern vision), and 3.5 million have low vision. The leading causes of low vision are diseases that are common in old age: age-related maculopathy, cataract, glaucoma, diabetic retinopathy, and optic nerve atrophy. Almost 10 percent of the population 75 to 84 years of age experiences low vision, while 25 percent of the population 85 and older is deemed to have low vision. Yet, low vision is not confined to the old; an estimated 1 million persons below age 65 experience low vision, and 72 thousand under 65 are blind (Genensky, 1994). An additional 9 million Americans live with other, milder forms of visual impairment that interfere with daily living tasks, especially in adverse lighting conditions (Benson and Marano, 1994).

An important aspect of a person's full participation in today's society is being able to conveniently and confidentially exchange currency in everyday transactions, as when using public transportation or making purchases (EBU, 1994). U.S. citizens with low vision experience a uniquely difficult task in that U.S. banknotes are remarkably uniform in size, color, and general design. The banknotes provide no basis for denominating by blind persons. Visual identification of denomination by people with low vision is generally so challenging that many revert to techniques used by people who are blind.

Blind people must trust others to inform them about the denominations of bills received. In the absence of features that are usable by blind people in the present bills, different denominations, once identified by a trusted sighted person, are sorted and stored in different ways.

The committee has identified 171 issuing authorities in the world producing banknotes. Many have specifically addressed the problems of people with low vision by incorporating such

features as variable size, variable color, and tactile markings. In some cases, a device is made available to blind people to aid in denominating banknotes. For example, England issues a size template, and Canada supplies its blind citizens with a portable banknote reader with audio output.

By 1996, the U.S. Treasury Department's Bureau of Engraving and Printing (BEP) expects to begin production of a new design for the $100 bill. In each succeeding year, working in descending order, a new design for a denomination will be introduced. By the year 2001, all six denominations currently in production ($100, $50, $20, $10, $5, and $1) will have been redesigned. A major motivation for this redesign is the incorporation of new security features to combat the threat of counterfeiting posed by the rapid development in advanced copying and imaging systems that allow even the unskilled user to make faithful full-color reproductions of documents.

This redesign presents an opportunity to introduce features into the design that will make U.S. banknotes more readily usable by visually disabled people. The timetable of the redesign also presents the opportunity to incorporate features that may require some development work into the smaller denominations within the current redesign sequence. To this end, the Committee on Currency Features Usable by the Visually Impaired was charged to:

• assess features that could be used by people who are visually disabled to recognize, denominate, and authenticate banknotes;
• recommend features that could reasonably be incorporated into banknotes using available technology;
• suggest strategies that should be instituted to make the recommended features most effective; and
• identify research needs in particularly promising areas that could lead to attractive future approaches.

In the study, three aspects of currency transactions were defined: recognition (is this meant to be a banknote?), denomination (how much is it worth?), and authentication (is it a real banknote?). An additional consideration of importance, especially with regard to the use of machines accepting cash, was the usefulness of features indicating orientation of the banknote. The primary goal of the committee was to recommend features that will help visually disabled people denominate banknotes, since reliable denomination is essential to their maintaining independence. The committee also evaluated features that will help these individuals authenticate banknotes, a process for which the individuals have the same needs as the normally sighted public. Such features could be added in addition to those included for use in denomination. The committee did not consider the entire mix of the circulating medium in the U.S. but focused solely on solutions to problems dealing with banknotes.

Over the course of this study, the committee solicited presentations from experts in visual and tactile perception and from representatives of organizations of blind people and people with low vision. The committee also obtained considerable data on currency features usable by visually disabled people and incorporated in the currency of other countries.

The committee generated an extensive list of features representing a wide range of sensory phenomena and application technologies. In assessing and prioritizing these features, the committee used an approach similar to that taken for the evaluation of counterfeit-deterrent features for currency in a previous study (NRC, 1993). In this approach, the set of requirements for a feature was converted into indicators or criteria that were considered in terms of relative importance. The application of the feature to different target populations was considered. Features of use to the broadest range of people were ranked highest.

The criteria for banknote feature effectiveness were first divided into target and evaluation criteria. The target population categories were blind, low vision, normally sighted in adverse lighting, and normally sighted in normal lighting. While visually disabled people were the primary group to be considered in regard to the features, normally sighted people would also benefit from any features implemented. The target function categories were recognition, denomination, authentication, and orientation. Orientation, though significant for use of ATMs (automated teller machines) and vending machines, was given lesser weight.

To evaluate feature effectiveness, technical evaluation criteria that were considered included reliability of readings, ease of use, device requirement, applicability to current bills, compatibility with proposed or existing overt security features, ability to cocirculate with current bills, and resistance to simulation. The unit cost of production, capital costs for the BEP and Federal Reserve banks, effects on note durability, feature survivability, availability for immediate or near-term implementation, and experience as proven banknote technology were considered as implementation evaluation criteria. The possibility of incorporation of a feature in the longer term with some additional development or research was also considered.

Further criteria were used for features that required the use of a device. Device criteria included the ability to recognize and denominate banknotes; accuracy, that is, the number of false positives and false negatives; portability; size; maintenance; cost; response time; power use; and longevity. Ability to authenticate was considered to be an important aspect of future development of devices. The output characteristics for devices should consider potential usage by non-English speakers and should take audible (multilingual), tactile, or visual form. Such devices might find application as point-of-sale aids for cash-accepting machines, which would reduce their unit cost.

The committee identified three features useful to visually disabled people that can be incorporated in U.S. banknotes without significant further research: banknote size that differs with denomination, large numerals indicating denomination, and banknote color that differs with banknote denomination. The committee received strong support from representatives of

organizations of and for visually disabled people for all three of these features. These features are all used in some form in currencies of other countries, and the technology for production is available today.

Because of the status of the ongoing redesign of the U.S. banknotes, the committee is concerned that features not included in the current redesign will not be implemented until a following redesign. The current design sequence will be complete with the issue of the redesigned bill of the smallest denomination in 2001.

To ease denomination of U.S. banknotes, the committee recommends the following features (presented in the order in which they are described in the text, with no priority implied):

• Banknote size as a key to denomination. Variation of both length and height would allow for more reliable absolute judgment about denomination, while variation of a single dimension would require a secondary cue, such as a size template, to achieve the same level of reliability.
• Large, high-contrast numerals on a uniform background. A large, open space will be required in the banknote design to allow for at least a single numeral, in a plain font, that is larger than one-half the current banknote height.
• Different predominant colors for each of the six denominations printed. A single color should dominate at least one face of the banknote and should be sufficiently distinguishable from the other colors in the banknote sequence to remain identifiable even in low lighting.
• Overt features that could lead to the development of effective, low-cost devices for examining banknotes. Inclusion of a denomination code is recommended to provide for development of devices for those who have difficulty using the recommended features and to add to the ability of visually disabled people to authenticate banknotes.

• All three of these features will serve the majority of the visually disabled—those with low vision. However, of the three features identified, banknote size that differs with denomination is the only one applicable to the needs of blind people.
• Large numerals and color, if applied in a distinct area, may also be used to indicate banknote orientation. No orientation information is given by different-sized banknotes.
• The Treasury Department should evaluate current approaches and conduct studies to determine the sizing needs of each denomination if the six denominations are to be sufficiently distinguishable. This may require, for instance, starting the sequence with a larger $100 banknote.
• The Treasury Department and the Federal Reserve should identify issues regarding the infrastructure of cash-handling machines to determine an appropriate timetable for the introduction of size-denominated banknotes.

• Development of features building on the substantial literature on visual and tactile processes and perception is warranted for near-term feature additions to banknotes. Highly directed, psychophysical/empirical technical work that addresses questions regarding optimum dimensions, optical contrast, location, colors, physical size, etc., for banknote applications should be undertaken.
• Specification of new or enhanced features should not be aimed at minimal levels of recognition performance (i.e., threshold levels) but should strive for sufficient differentiation to permit rapid, relatively effortless performance, with differences between denominations designed to be several times greater than the difference threshold.
• The committee recommends that research be performed to identify combinations of features that enhance denomination and orientation and, perhaps, authentication.
• In reviewing the needs of the 3.7 million U.S. citizens with low vision, the committee observed that many documents issued by government agencies, such as passports, visas, postage stamps, and food stamps, could better serve those with low vision if features similar to those discussed in the report were incorporated in their design. Indeed, in some cases, features not considered sufficiently robust for application in banknote design might find early application in other government documents.
• The public education campaign accompanying any introduction of new banknote features for visually disabled people would provide a good opportunity for the private sector to consider these types of features for packaging design and related applications.

• The committee urges research on the development of durable tactile features, such as ones printed with "transparent" ink. Transparent-ink tactile marks can be implemented with minimal design changes and so offer flexibility in timing the feature's incorporation.
• The committee recommends research into the implementation issues of holes to denominate banknotes, including the production of durable holes and the psychological questions regarding issuing and using banknotes containing holes.

• The committee recommends research to define the threshold and accuracy of reading for the types of low-relief tactile features that are likely to be applicable to banknotes.
• The committee recommends research in the area of enhanced threads, planchettes, or films that would improve devices for examining banknotes.
• The committee recommends that long-term research into advanced features be initiated as possible directions become evident from technology development.
• The committee recommends that analysis regarding the incorporation of advances in microelectronics, nanotechnology, molecular electronics, materials, photonics, and magnetics in device development be an ongoing effort. Research and development efforts directed toward

• deriving very sophisticated but inexpensive, reliable, accurate, and inconspicuous devices should be encouraged.
• The BEP should follow the technical work underway by organizations and institutions concerned with the problems of people who are visually disabled and their proposed solutions to those problems, and it should develop a process to assess the applicability of progress in these areas to banknote production.

If the features incorporated in a new design are to be maximally effective, a carefully planned implementation strategy must be developed as the features are evaluated and considered for inclusion. Important aspects of an implementation strategy include the following:

• In selecting features for implementation, the Treasury Department and the Federal Reserve should involve appropriate user groups as early as possible to ensure selection of those features most likely to be used by, and useful to, the target population. The design of any field test should include a cross-section of the target population appropriate to the feature being tested.
• The field test should be broad enough in scope to show not only that the new feature permits recognition under optimal conditions but that rapid, relatively effortless and confidential currency identification are possible across a wide range of everyday circumstances.
• Data gathered from focus groups should be used to help guide the public education campaign that must be a part of the implementation of any new currency feature.
• An appropriate schedule for any introduction of graded sizes of banknotes follows that planned by the BEP for the banknote redesign, beginning with the $100. Since this banknote would be the largest in the series and represents the smallest production volume, gradual introduction of size-denominated banknotes over the course of six to seven years would allow time for the commercial currency handling industry to prepare for the change.
• In the early stages of distributing sized banknotes, templates would have to be made available to visibly disabled people. The templates might be distributed through banks or appropriate organizations of visually disabled people.

Benson, V., and M.A. Marano. 1994. Current estimates from the National Health Interview Survey. National Center for Health Statistics, January 1994. Vital and Health Statistics Series 10(189):95.

EBU (European Blind Union). 1994. A report of the European Blind Union Expert Working Group on Currency: Recommendations for the Design of the ECU. Paris, France: EBU.

Genensky, S. 1994. Personal communication to the Committee on Currency Features Usable by the Visually Impaired. March 30, 1994.

NRC (National Research Council). 1993. Counterfeit Deterrent Features for the Next-Generation Currency Design. National Materials Advisory Board, NRC. Washington, D.C.: National Academy Press.