Accessible Design of Consumer Products

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Guidelines for the Design of Consumer Products to Increase Their Accessibility to People with Disabilties or Who Are Aging

Working Draft 1.7 -- 1992

Compiled for The AD HOC Industry-Consumer-Researcher Work Group of the Consumer Product Design Guidelines Project by Gregg C. Vanderheiden and Katherine R. Vanderheiden Support for the preparation and dissemination of this document has been provided by the National Institute of Disability and Rehabilitation Research (NIDRR), US Dept. of Education\ under grant #G00850036 and by the Assistive Devices Division, Consumer Electronics Group, Electronic Industries Association.

This document is being sent out specifically for comment and suggested revisions from industry, consumers and researchers. Please feel free to mark up, comment, improve or take exception to the document in any way you see fit and send your comments to us. All responses and comments can be kept in strict confidence, allowing you to comment freely as individuals or organizations with anonymity. Your input is important to this process. Send comments to

CONSUMER PRODUCTS GUIDELINES PROJECT
Trace R & D Center
2107 Engineering Centers Bldg.
1550 Engineering Dr.
University of Wisconsin - Madison
Madison, WI 53706
Attn: Gregg C. Vanderheiden Ph.D.

©1991 Copyright Board of Regents, University of Wisconsin System

NOTE: To facilitate this document's review and use, you are free to duplicate and disseminate it freely. You may also excerpt ideas and materials from it freely. However, please send us a copy of your work as well for our information and interest.

Some of the charts and concepts in this document are taken from other authors and publications. These are so marked, and separate permission must be sought directly from those authors or publications before use (apart from copying this whole document).

The opinions expressed in this document do not necessarily reflect the opinions of NIDRR, the Assistive Devices Division of EIA or the individuals listed as contributors. Nor do all of the opinions necessarily represent the opinion of the compilers, since this document represents a compendium of input from many sources.

ABOUT THE PROJECT WORK GROUP

The AD HOC Industry-Consumer-Researcher Work Group is an open group composed of those individuals interested in more accessible consumer product design and contributing to the development and refinement of these guidelines. The work group is headquartered at the Trace R & D Center at the University of Wisconsin - Madison. Anyone can join by reviewing, and submitting comments to correct, elaborate or extend these guidelines. Communications of the ad hoc work group are carried out by mail to facilitate participation by industry and consumer representatives who would not otherwise be able to attend particular meetings or conferences. To participate in the work group, simply send your comments, ideas, corrections or extensions to the guidelines to the address on the cover of this report.

ACKNOWLEDGEMENTS

Many individuals contributed to the development of these guidelines, both formally and informally, including students who participated in an Industrial Engineering Department Seminar on Design and Human Disability and Aging at the University of Wisconsin - Madison. Among the professionals, consumers, industry representatives and students contributing to these guidelines are:

Karen Athens
Keith Bednar
Jane Berliss
Lori Beth
Mary Ann Bird
Peter Borden
Eli Chu
Suruedee Chumroum
Raúl Colón
Cynthia Cress
Joanne Deda
Thomas Findley
Jackie Finley
Clint Gibler
Bob Glass
Sue Gmeinder
Paul John Grayson
Mickey Greenberg
Jackie Greshik
Debra A. Griffith
Andy Hesselbach
Ken Jelinek
One-Jang Jeng
Jeff Jentz
Andrea Johnson
Tim Jones
Dennis Jones
Tracy Kidd
Kimberly Kline
Fritz Klode
Jeff Kolff
Yueh-Chuan Kung
Dennis La Buda
Chris LaPorte
Charles Lee
David J. Lee
Seongil Lee
Patti Lindstrom
Fred Lupton
Robert Lynch
Diane Meyers
James Mueller
Young Lae Park
Lawrence Scadden
Joseph Schauer
Debbie Schlais
Lisa Schroeder-Omar
Debbie Sherman
Paul Sura
Jeff Tackes
Sidney Tang
Christine Thompson
Mike Thompson
Michelle S. Vandall
John Ward
Dawn Wadzinski
Steven Wiker
Greg Wierman
Marcy Worzala
Chien-Ling Yang
Thomas Yen
Dave Zehel

A special thanks to Christine J. Thompson, who assisted in the preparation of many of the graphics in this document.

ABOUT THE AUTHORS

The authors of this document are too numerous and diverse to easily identify and include the compilers, those listed in the acknowledgements, those cited in the text and an even greater number of individuals whose ideas have filtered down through the grapevine and are captured here. This document represents their ideas as compiled and extended by Gregg C.Vanderheiden and Katherine R. Vanderheiden.

Gregg Vanderheiden is an associate professor in the Industrial Engineering Department's Human Factors Program at the University of Wisconsin-Madison and Director of the Trace Research and Development Center at the University (a Rehabilitation Engineering Center focusing on access to communication, computer and electronic devices by people with disabilities). Dr. Vanderheiden has been active in the field of technology and disability for over 20 years, has published numerous papers, chapters and books and has been principal investigator on over 40 grants and contracts in the area.

Katherine Vanderheiden is an independent business and professional education consultant. She is a CPA with 10 years experience in industry, including public accounting, serving as a computer systems implementation coordinator for a large hospital and developing training courses and materials for internal and industry use in her capacity as Manager in the Education Consulting Division of Arthur Andersen & Co.

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CONTENTS

PART I - Introduction

• Background
• Purpose of this Document
• What is Accessible Design?
• Four Ways to Make Products More Accessible
  1. Direct Accessibility
  2. Accessibility via Standard Options or Accessories
  3. Compatibility With Third Party Assistive Devices
  4. Facilitation of Custom Modifications
• The Best Approach

PART II - Disabilities and Specific Barriers to Accessibility

• Visual Impairments
• Hearing Impairments
• Physical Impairments
• Cognitive/Language Impairments
• Seizure Disorders
• Multiple Impairments

PART III - Guidelines for More Accessible Design

• Structure and Organization of the Guidelines
• Designer's Dilemma: Availability and Meaningfulness of Numbers
• Solomon's Trap
• Resolving Conflicting Recommendations
• SECTION 1 OUTPUT / DISPLAYS
• SECTION 2 INPUT/CONTROLS
• SECTION 3 MANIPULATIONS
• SECTION 4 DOCUMENTATION
• SECTION 5 SAFETY

References and Resources

Appendix: Guidelines Checklist

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GUIDELINES BY SECTION

SECTION 1 - OUTPUT / DISPLAYS

Maximize the number of people who can/will ...

SECTION 2 - INPUT / CONTROLS

Maximize the number of people who can ...

SECTION 3 - MANIPULATIONS

Maximize the number of people who can ...

SECTION 4 - DOCUMENTATION

Maximize the number of people who can ...

SECTION 5 - SAFETY

Maximize the number of people who can ...

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PART I - Introduction

Background

Beginning in 1984, joint government/industry efforts have attempted to address the accessibility of standard computer hardware and software by people with disabilities. One of the major results of these efforts was the development of design guidelines for use by computer manufacturers and software developers . These guidelines were prepared at the request of the computer companies to assist them in better understanding accessibility problems in computer design and to identify commercially practical strategies for making their products more accessible. The guidelines were developed using a cooperative industry-consumer-researcher-government consortium in order to provide the best information from all angles. The resulting guidelines (titled: Considerations in the Design of Computers and Operating Systems to Increase Their Accessibility to People with Disabilities) have been used by most major computer manufacturers in their ongoing efforts to make their products more accessible and usable by people with various types and degrees of disability. The Considerations document is a working document, and as such is continually evolving and improving (the current version is 4.2).

Purpose of This Document

This document represents a similar cooperative effort to develop design guidelines for the design of "consumer products." For this document, consumer products are defined as appliances and other electronic and mechanical devices available to the mass market for use in the home, school, office, or for use by the general public in the community. The purpose of these guidelines is 1) to point out problems encountered by people with various disabilities in using standard consumer products, and 2) to propose design alternatives which will result in increased usability of standard products by people with disabilities.

As with the computer guidelines, this document is designed to be purely informational in nature, and has been developed at industry's request to facilitate product designers' efforts to make their products more accessible. It represents the compilation of information from many sources and, as a working document, is under continual revision. To that end, comments and suggested revisions are solicited from all readers, particularly from product designers.

What is Accessible Design?

"Accessible Design" is the term used for the process of extending mass market product design to include people who, because of personal characteristics or environmental conditions, find themselves on the low end of some dimension of performance (e.g., seeing, hearing, reaching, manipulating). Accessible Design is not (or should not be) separate from standard mass market design. Rather it is an extension or elaboration of general design principles to cover a wider range of human abilities/limitations than has traditionally been included in product design.

Thus Accessible Design is a subset of what is termed Universal Design. Where Universal Design covers the design of products for all people and encompasses all design principles, Accessible Design focuses on principles that extend the standard design process to those people with some type of performance limitation (the lower ability tail of Universal Design).

Accessible Design is a balancing act. To begin with, we must acknowledge that it is not possible to design everything so that it can be used by everyone. There will always be someone with a combination of severe physical, sensory and cognitive impairments who will not be able to use it. However, it is equally unreasonable to rely on the existence (or development) of special designs for each major product to accommodate each one of the immense variety of disabilities (and combinations of disabilities). This makes it necessary to look toward a combination of approaches for meeting the needs of people with disabilities, ranging from the incorporation of features into products that will make them directly usable ("from the box") by more people with disabilities to the inclusion of features that make them easier to modify for accessibility.

Four Ways to Make Products More Accessible

Four different approaches to making products more accessible are discussed in this section and reflected in the Guidelines. In any one product, it may be necessary to use one or a combination of these approaches to achieve the desired level of accessibility. These approaches, in order of desirability, are:

1. Direct Accessibility
2. Accessibility via Standard Options or Accessories (from the manufacturer)
3. Compatibility with Third Party Assistive Devices
4. Facilitation of Custom Modifications

1. Direct Accessibility:

• For most types or degrees of impairment, there are simple and low cost (or no cost) adaptations to product designs which can significantly increase their accessibility and usefulness to individuals with functional impairments. By incorporating these design modifications into the initial product design, the standard product can be more accessible directly "out of the box."
• Inclusion of these design features or approaches in the standard product can be of substantial benefit to society as a whole to the extent it enables individuals with disabilities to lead more independent and productive lives. As an additional bonus, it has often been found that designs which are accessible to people with more limited abilities may benefit other users (without disabilities or impairments) as well by reducing fatigue, increasing speed, decreasing the number of errors made and decreasing learning time.
• Some examples.

  In the personal computer industry, particular attention has been focused on Accessible Design in recent years, and access features are beginning to show up as direct components of standard computer products. A "MouseKeys" feature, for example, is now a standard part of all Apple Macintosh™ computers shipped. This feature, which can be invoked directly from the keyboard, allows the user to move the cursor across the screen via the numeric keypad rather than the mouse. Individuals who do not have the motor control necessary to operate a mouse can use this feature (which is built into all Macintoshes) to access the Macintosh. Because the feature is implemented as an extension to the computer's operating system, it costs nothing to include as part of the product. Since "MouseKeys" became available, many able-bodied users have found it useful as well because of its capability for precise one-pixel positioning, which was not previously available.

  Other examples of direct accessibility include MacDonald's, who embossed braille characters on the tops of its soft drink cup covers along with the letters labelling the pushdown buttons on the lid that indicate whether the drink is diet, etc., and Proctor-Silex, who embossed braille characters on the bottom of some of its bowls indicating the size (quarts) of the bowl.

2. Accessibility via Standard Options or Accessories (from the manufacturer):

• Sometimes it is not possible to design the standard product to make it directly accessible for some disability populations. Alternatives to standard design may be identified, but offering all of them may not be practical due to some alternatives being mutually exclusive, too expensive, or awkward as a standard product.
• When this occurs, it may be more effective to make these adaptations or alternatives available as standard options or accessories from the manufacturer. These may be extra-cost, special order items, or preferrably, items available free on request. These special features or accessories should be listed and described in the standard documentation that comes with the product. They could also be listed in advertising for the product.
• An example.

  Microwave ovens are often made with smooth glass control panels. That is, there are no tactilely discernable buttons. This can present a problem for people with visual impairments. Ideally, the control panel should be designed with ridges around each button and some type of tactile identification of button function. If this is not possible, the manufacturer may make available either a raised letter or braille overlay. These could be available free upon request. (Information on how to order the optional accessories should then be prominently presented in the product installation and operating instructions). The Sharp Carousel II (TM) is one such microwave that offers a braille overlay as an option.

3. Compatibility With Third Party Assistive Devices:

3a. Compatibility with Special Interfaces or Accessories

• Sometimes direct accessibility, or even the use of standard options, is impractical for the mass market producer to provide for all disability types and degrees. This is particularly true for individuals with severe or multiple impairments (e.g., a person with a severe physical disability may be unable to use a standard keyboard even with accessibility features built in). In these cases, special interfaces or accessories may be available from third party assistive device manufacturers.
• Some examples.

  The mass market manufacturer can facilitate the efforts of third party manufacturers in a number of ways, including using standard approaches, providing appropriate connection points, providing advance access to new versions of products, and providing technical assistance in understanding and properly attaching accessories to the product. Consideration in the design of a keyboard, for example, could make it easier for third parties to develop keyguards and other keyboard accessories.

3b. Compatibility with General Purpose Assistive Devices

• In some cases, people with particular disabilities may already have general purpose assistive devices which they would like to be able to use in conjunction with a product (e.g., a person with an eye gaze communication aid would like to be able to use it in conjunction with home electronic appliances; an individual with artificial hands or a hook would like to be able to operate the handles on appliance doors; a blind person with a dynamic braille display would like to use it with home information systems). Unfortunately, it is often difficult or impossible to connect the assistive devices to standard products.
• Cooperation between mass manufacturers and assistive device manufacturers could result in standard or built-in product connection points (connectors or infra-red links) which facilitate the connection of special devices as well as properly designed hardware to facilitate the use of assistive manipulation devices.
• An example.

  Many people with physical disabilities cannot use standard computer keyboards. Some of these people would require more extensive modifications than would be possible using the first two accessibility approaches discussed. Currently, there are assistive device manufacturers who make alternative input devices to fit people with a variety of severe physical disabilities. However, the manufacturers of these assistive devices have always had problems ensuring that the devices would work with standard, commercially available computers. As part of the effort by the computer industry to cooperate with manufacturers of assistive devices, both IBM & Microsoft Corporation now distribute an extension to their operating systems (DOS & Windows) called "SerialKeys." This extension allows people to connect alternative input devices to the serial port of the standard personal computer in a way which makes input to the serial port look like it is coming directly from the standard keyboard and mouse. In this fashion, the user with a disability can completely access and control the computer and all of its software from an alternate input system without touching the standard keyboard or mouse.

4. Facilitation of Custom Modifications:

• There may be some cases where all the other approaches to Accessible Design prove to be impractical or uneconomical, most likely for people with combinations or severe disabilities.
• In such cases, custom modifications of the product, either by the product manufacturer or a third party, may be the best solution. Standard product manufacturers should facilitate this as much as they can. For example, leaving room for special attachments or labels, documenting hooks or places to patch into hardware or software, publishing information on safe or effective ways to modify products, or honoring warrantees for products which have been modified for accessibility but where the modification did not result in the problem.
• An Example:

  After-market adaptation of automobiles (particularly vans) for use by drivers with physical impairments is being facilitated in this way. As more standards are developed through cooperative efforts by auto manufacturers, adaptive specialists, and consumers, possibilities for help from the auto manufacturers will improve. Currently, Chrysler pays the first $500 for after-market adaptation of its vans for people with disabilities. General Motors now pays up to $1,000 reimbursement of adaptive equipment and installation costs on eligible vehicles, and provides listings of driver assessment facilities, mobility equipment dealers, and organizations offering services in transportation, as well as a GM wheelchair compatibility listing and resource video.

The Best Approach

Of the four approaches to Accessible Design, the first type, direct accessibility "from the box," is the best where it is possible. It allows the greatest access to products by persons with disabilities at the lowest cost. It also allows them to access products in public places where they could not otherwise modify the products to meet their particular needs. It also removes the stigma of "special" aids or modifications. This is especially important for older users who do not want to be labeled "disabled" even though their abilities are weakening.

It should also be noted that most of us become temporarily "disabled" in a number of ways throughout our lives. Sometimes it is by accident, such as a broken arm or eye injury. Sometimes it is by circumstance, such as operating things in the dark where we can't see well, in loud environments (vacuuming or teenagers) where we can't hear well, with things in our arms where we can't reach well, when we're tired or on cold medication and can't think well, etc. Only those products which were designed to be more easily used directly "from the box" (#1 above) will be of use to us then. As mentioned above, more accessible designs are also usually easier to use by everyone all the time - but only if the ease of use is directly built in.

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PART II - Disabilities and Specific Barriers to Accessibility

Prior to reviewing the Guidelines presented in Part III, the reader who is not familiar with the demographics, causes and effects of major types of disabilities would benefit greatly from reviewing this section. The Guidelines assume a basic familiarity with this information. In addition, it is likely that new advances in design are not anticipated by the Guidelines. In those cases, knowledge of the basic characteristics of various disabilities will enable manufacturers to anticipate the effect of major design changes on their products' accessibility

A significant portion of our population (over thirty million in the U.S.) has impairments which reduce their ability to effectively or safely use standard consumer products. These impairments may be acquired at birth or through accident or disease. Note that many impairments which result in disabilities are associated with aging. This is especially significant, as the population as a whole is growing older. Although there is a tremendous variety of specific causes, as well as combinations and severity of disabilities, we can most easily relate their basic impact to the use of consumer products by looking at four major categories of impairment. The four categories are:

• Visual Impairments
• Hearing Impairments
• Physical Impairments
• Cognitive/Language Impairments

In addition, we will discuss the special case of seizure disorders as well as some of the common situations of multiple impairments.

Visual Impairments

Visual impairment represents a continuum, from people with very poor vision, to people who can see light but no shapes, to people who have no perception of light at all. However, for general discussion it is useful to think of this population as representing two broad groups: those with low vision and those who are legally blind. There are an estimated 8.6 million people with visual impairments (3.4% of the U.S. population). In the elderly population the percentage of persons with visual impairments is very high.

A person is termed legally blind when their visual acuity (sharpness of vision) is 20/200 or worse after correction, or when their field of vision is less than 20 degrees in the best eye after correction. There are approximately 580,000 people in the U.S. who are legally blind.

Low vision includes problems (after correction) such as dimness of vision, haziness, film over the eye, foggy vision, extreme near- or farsightedness, distortion of vision, spots before the eyes, color distortions, visual field defects, tunnel vision, no peripheral vision, abnormal sensitivity to light or glare, and night blindness. There are approximately 1.8 million people in the U.S. with severe visual impairments who are not legally blind.

Many diseases causing severe visual impairments are common in those who are aging (glaucoma, cataracts, macular degeneration, and diabetic retinopathy). With current demographic trends toward a larger proportion of elderly, the incidence of visual impairments will certainly increase.

Functional Limitations Caused by Visual Impairments

Those who are legally blind may still retain some perception of shape and contrast or of light vs. dark (the ability to locate a light source), or they may be totally blind (having no awareness of environmental light).

Those with visual impairments have the most difficulty with visual displays and other visual output (e.g., hazard warnings). In addition, there are problems in utilizing controls where labelling or actual operation is dependent on vision (e.g., where eye-hand coordination is required, as with a computer "mouse"). Written operating instructions and other documentation may be unusable, and there can be difficulties in manipulation (e.g., insertion/placement, assembly).

Because many people with visual impairments still have some visual capability, many of them can read with the assistance of magnifiers, bright lighting and glare reducers. Many such people with low vision are helped immensely by use of larger lettering, sans-serif typefaces, and high contrast coloring.

Those with color blindness may have difficulty differentiating between certain color pairs. This generally doesn't pose much of a problem except in those instances when information is color coded or where color pairs are chosen which result in poor figure ground contrast.

Key coping strategies for people with more severe visual impairments include the use of braille and large raised lettering. Note, however, that braille is preferred by only 10% of blind people (normally those blind from early in life). Raised lettering must be large and is therefore better for indicating simple labels than for extensive text.

Hearing Impairments

Hearing impairment is one of the most prevalent chronic disabilities in the U.S. Approximately 22 million people in the U.S. (8.2%) have hearing impairments. Of those, 2.4 million have severe to profound impairments.

Hearing impairment means any degree and type of auditory disorder, while deafness means an extreme inability to discriminate conversational speech through the ear. Deaf people, then, are those who cannot use their hearing for communication. People with a lesser degree of hearing impairment are called hard of hearing. Usually, a person is considered deaf when sound must reach at least 90 decibels (5 to 10 times louder than normal speech) to be heard, and even amplified speech cannot be understood.

Hearing impairments can be found in all age groups, but loss of hearing acuity is part of the natural aging process. 23% of those aged 65 to 74 have hearing impairments, while almost 40% over age 75 have hearing impairments. The number of individuals with hearing impairments will increase with the increasing age of the population and the increase in the severity of noise exposure.

Hearing impairment may be sensorineural or conductive. Sensorineural hearing loss involves damage to the auditory pathways within the central nervous system, beginning with the cochlea and auditory nerve, and including the brain stem and cerebral cortex (this prevents or disrupts interpretation of the auditory signal). Conductive hearing loss is damage to the outer or middle ear which interferes with sound waves reaching the cochlea. Causes include heredity, infections, tumors, accidents and aging (presbycusis, or "old hearing").

Functional Limitations Caused by Hearing Impairments

The primary difficulty for individuals with hearing impairment in using standard products is receiving auditory information. This problem can be compensated for by presenting auditory information redundantly in visual and/or tactile form. If this is not feasible, an alternative solution to this problem would be to provide a mechanism, such as a jack, which would allow the user to connect alternative output devices. Increasing the volume range and lowering the frequency of products with high pitched auditory output would be helpful to some less severely impaired individuals. (Progressive hearing loss usually occurs in higher frequencies first.)

Although not prevalent yet, there is much talk of using voice input on commercial products in the future. This, too, will present a problem for many deaf individuals. While many have some residual speech, which they work to maintain, those who are deaf from birth or a very early age often are also nonspeaking or have speech that cannot be recognized using current voice input technology. Thus, alternatives to voice input will be necessary to these individuals to access products with voice input.

Familiar coping strategies for hearing impaired people include the use of hearing aids, sign language, lipreading and TDD's (telecommunication devices for the deaf). Some hearing aids are equipped with a "T-coil" as well, which provides direct inductive coupling with a second coil (such as in a telephone receiver) in order to reduce ambient noise. Some other commercial products could make use of this capability.

ASL (American Sign Language) is commonly used by people who are deaf. It should be noted, however, that this is a completely different language from English. Thus, deaf people who primarily use ASL may understand English only as a second language, and may therefore not be as proficient with English as native speakers.

Finally, telecommunication devices for the deaf (TDD's) are becoming more common in households and businesses as a means for deaf and hard of hearing people to communicate over the phone. TDD's have always used the Baudot code, but newer ones receive both Baudot and ASCII.

Physical Impairments

Functional Limitations Caused by Physical Impairments

Problems faced by individuals with physical impairments include poor muscle control, weakness and fatigue, difficulty walking, talking, seeing, speaking, sensing or grasping (due to pain or weakness), difficulty reaching things, and difficulty doing complex or compound manipulations (push and turn). Individuals with spinal cord injuries may be unable to use their limbs and may use "mouthsticks" for most manipulations. Twisting motions may be difficult or impossible for people with many types of physical disabilities (including cerebral palsy, spinal cord injury, arthritis, multiple sclerosis, muscular dystrophy, etc.).

Some individuals with severe physical disabilities may not be able to operate even well-designed products directly. These individuals usually must rely on assistive devices which take advantage of their specific abilities and on their ability to use these assistive devices with standard products. Commonly used assistive devices include mobility aids (e.g., crutches, wheelchairs), manipulation aids (e.g., prosthetics, orthotics, reachers) communication aids (e.g., single switch-based artificial voice), and computer/device interface aids (e.g., eyegaze-operated keyboard).

Nature and Causes of Physical Impairments

Neuromuscular impairments include:

• paralysis (total lack of muscular control in part or most of the body),
• weakness (paresis; lack of muscle strength, nerve enervation, or pain), and
• interference with control, via spasticity (where muscles are tense and contracted), ataxia (problems in accuracy of motor programming and coordination), and athetosis (extra, involuntary, uncontrolled and purposeless motion).

Skeletal impairments include joint movement limitations (either mechanical or due to pain), small limbs,missing limbs, or abnormal trunk size.

Some major causes of these impairments are:

Arthritis. Arthritis is defined as pain in joints, usually reducing range of motion and causing weakness. Rheumatoid arthritis is a chronic syndrome. Osteoarthritis is a degenerative joint disease. 31.6 million people in the U.S. suffer from rheumatic disease. The incidence of all forms of arthritis is now estimated at 900,000 new cases per year.

Cerebral Palsy (CP). Cerebral palsy is defined as damage to the motor areas of the brain prior to brain maturity (most cases of CP occur before, during or shortly following birth). There are more than 750,000 in the U.S. with CP (children and adults), and 15,000 infants are born each year with CP. CP is a type of injury, not a disease (although it can be caused by a disease), and does not get worse over time; it is also not "curable." Some causes of cerebral palsy are high temperature, lack of oxygen, and injury to the head. The most common types are: (1) spastic, where the individual moves stiffly and with difficulty, (2) ataxic, characterized by a disturbed sense of balance and depth perception, and (3) athetoid, characterized by involuntary, uncontrolled motion. Most cases are combinations of the three types.

Spinal Cord Injury. Spinal cord injury can result in paralysis or paresis (weakening). The extent of paralysis/paresis and the parts of the body effected are determined by how high or low on the spine the damage occurs and the type of damage to the cord. Quadriplegia involves all four limbs and is caused by injury to the cervical (upper) region of the spine; paraplegia involves only the lower extremities and occurs where injury was below the level of the first thoracic vertebra (mid-lower back). There are 150,000 to 175,000 people with spinal cord injuries in the U.S., with projected annual increases of 7,000 - 8,000. 47% of spinal cord injuries result in paraplegia; 53% in quadriplegia. Car accidents are the most frequent cause (38%), followed by falls and jumps (16%) and gunshot wounds (13%).

Head Injury (cerebral trauma). The term "head injury" is used to describe a wide array of injuries, including concussion, brain stem injury, closed head injury, cerebral hemorrhage, depressed skull fracture, foreign object (e.g., bullet), anoxia, and post-operative infections. Like spinal cord injuries, head injury and also stroke often results in paralysis and paresis, but there can be a variety of other effects as well. Currently about one million Americans (1 in 250) suffer from effects of head injuries, and 400,000 - 600,000 people sustain a head injury each year. However, many of these are not permanently or severely disabled.

Stroke (cerebral vascular accident; CVA). The three main causes of stroke are: thrombosis (blood clot in a blood vessel blocks blood flow past that point), hemorrhage (resulting in bleeding into the brain tissue; associated with high blood pressure or rupture of an aneurism), and embolism (a large clot breaks off and blocks an artery). The response of brain tissue to injury is similar whether the injury results from direct trauma (as above) or from stroke. In either case, function in the area of the brain affected either stops altogether or is impaired.

Loss of Limbs or Digits (Amputation or Congenital). This may be due to trauma (e.g., explosions, mangling in a machine, severance, burns) or surgery (due to cancer, peripheral arterial disease, diabetes). Usually prosthetics are worn, although these do not result in full return of function. The National Center for Health Statistics of the U.S. Public Health Service estimated a prevalence of 311,000 amputees in 1970. An incidence of approximately 43,000 new amputations per year is estimated, of which 77% occur in males, and 90% involve the legs. 40% of amputations are above the knee, 50% are below the knee, and 10% are at the hip.

Parkinson's Disease. This is a progressive disease of older adults characterized by muscle rigidity, slowness of movements, and a unique type of tremor. There is no actual paralysis. The usual age of onset is 50 to 70, and the disease is relatively common - 187 cases per 100,000.

Multiple Sclerosis (MS). Multiple sclerosis is defined as a progressive disease of the central nervous system characterized by the destruction of the insulating material covering nerve fibers. The problems these individuals experience include poor muscle control, weakness and fatigue, difficulty walking, talking, seeing, sensing or grasping objects, and intolerance of heat. Onset is between the ages of 10 and 40. This is one of the most common neurological diseases, affecting as many as 500,000 people in the U.S. alone.

ALS (Lou Gehrig's Disease). ALS (Amyotrophic Lateral Sclerosis) is a fatal degenerative disease of the central nervous system characterized by slowly progressive paralysis of the voluntary muscles. The major symptom is progressive muscle weakness involving the limbs, trunk, breathing muscles, throat and tongue, leading to partial paralysis and severe speech difficulties. This is not a rare disease (5 cases per 100,000). It strikes mostly those between age 30 and 60, and men three times as often as women. Duration from onset to death is about 1 to 10 years (average 4 years).

Muscular Dystrophy (MD). Muscular dystrophy is a group of hereditary diseases causing progressive muscular weakness, loss of muscular control, contractions and difficulty in walking, breathing, reaching, and use of hands involving strength. About 4 cases in 100,000 are reported.

Cognitive/Language Impairments

Functional Limitations Caused by Cognitive/Language Impairments

The type of cognitive impairment can vary widely, from severe retardation to inability to remember, to the absence or impairment of specific cognitive functions (most particularly, language). Therefore, the types of functional limitations which can result also vary widely.

Cognitive impairments are varied, but may be categorized as memory, perception, problem-solving, and conceptualizing disabilities. Memory problems include difficulty getting information from short-term storage, long term and remote memory. This includes difficulty recognizing and retrieving information. Perception problems include difficulty taking in, attending to, and discriminating sensory information. Difficulties in problem solving include recognizing the problem, identifying, choosing and implementing solutions, and evaluation of outcome. Conceptual difficulties can include problems in sequencing, generalizing previously learned information, categorizing, cause and effect, abstract concepts, comprehension and skill development. Language impairments can cause difficulty in comprehension and/or expression of written and/or spoken language.

There are very few assistive devices for people with cognitive impairments. Simple cuing aids or memory aids are sometimes used. As a rule, these individuals benefit from use of simple displays, low language loading, use of patterns, simple, obvious sequences and cued sequences.

Types and Causes of Cognitive/Language Impairments

Mental Retardation. A person is considered mentally retarded if they have an IQ below 70 (average IQ is 100) and if they have difficulty functioning independently. An estimated 3% of Americans are mentally retarded. For most, the cause is unknown, although infections, Down Syndrome, premature birth, birth trauma, or lack of oxygen may all cause retardation. Those considered mildly retarded (80-85%) have an IQ between 55 and 69 and are considered educable, achieving 4th to 7th grade levels. They usually function well in the community and hold down semi-skilled and unskilled jobs. People with moderate retardation (10%) have an IQ between 40 and 54 and are trainable in educational skills and independence. They can learn to recognize symbols and simple words, achieving approximately a 2nd grade level. They often live in group homes and work in sheltered workshops. People with severe or profound retardation represent just 5-10% of this population.

Language and Learning Disabilities. Aphasia, an impairment in the ability to interpret or formulate language symbols as a result of brain damage, is frequently caused by left cerebral vascular accident (stroke) or head injury. Specific learning disabilities are chronic conditions of presumed neurological origin which selectively interfere with the development, integration, and/or demonstration of verbal and/or non-verbal abilities. Many people with learning disabilities are highly intelligent aside from their specific learning disability. 1-8% of school-aged children and youth have specific learning disabilities.

Age-Related Disease. Alzheimer's disease is a degenerative disease that leads to progressive intellectual decline, confusion and disorientation. Dementia is a brain disease that results in the progressive loss of mental functions, often beginning with memory, learning, attention and judgment deficits. The underlying cause is obstruction of blood flow to the brain. Some kinds of dementia are curable, while others are not.

Seizure Disorders

A number of injuries or conditions can result in seizure disorders. Epilepsy is a chronic neurological disorder. It is reported that approximately 1 person in 15 has a seizure of some sort during his life, and between .5% and 1.5% of the general population have chronic, recurring seizures. A seizure consists of an explosive discharge of nervous tissue, which often starts in one area of the brain and spreads through the circuits of the brain like an electrical storm. The seizure discharge activates the circuits in which it is involved and the function of these circuits will determine the clinical pattern of the seizure. Except at those times when this electrical storm is sweeping through it, the brain is working perfectly well in the person with epilepsy. Seizures can vary from momentary loss of attention to grand mal seizures which result in the severe loss of motor control and awareness. Seizures can be triggered in people with photosensitive epilepsy by rapidly flashing lights, particularly in the 10 to 25 Hz range.

Multiple Impairments

It is common to find that whatever caused a single type of impairment also caused others. This is particularly true where disease or trauma is severe, or in the case of impairments caused by aging.

Deaf-blindness is one commonly identified combination. Most of these individuals are neither profoundly deaf nor legally blind, but are both visual and hearing impaired to the extent that strategies for deafness or blindness alone won't work. People with developmental disabilities may have a combination of mental and physical impairments that result in substantial functional limitations in three or more areas of major life activity. Diabetes, which can cause blindness, also often causes loss of sensation in the fingers. This makes braille or raised lettering impossible to read. Cerebral palsy is often accompanied by visual impairments, by hearing and language disorders, or by cognitive impairments.

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PART III - Guidelines for More Accessible Design

Structure and Organization of the Guidelines

In order to facilitate use by product design teams, this section is organized functionally rather than by disability area. Functional categories are as follows:

Each guideline is phrased as an objective, followed by a statement of the problem(s) faced by people with disabilities. The problem statement is accompanied by more specific examples. Next, "design options and ideas" are presented to provide some suggestions as to how the objective could be achieved. Readers are encouraged to think of other ideas. Finally, additional data and specific information, along with illustrations, are presented at the end of each guideline.

The guidelines are stated as generically as possible. Therefore, all, some or none of the design options and ideas presented may apply in the case of any specific product. The recommended approach is to implement those options which together go the longest way toward achieving the objective of the guideline for your product. It is understood that this is not an ideal world, so it may currently be too expensive to implement all those ideas which would best achieve the objective. It is also anticipated that there will be other ways of meeting accessibility objectives than those discussed here, and such discoveries are encouraged. We would like to hear of them so that they can be included in future releases of these Guidelines.

Designer's Dilemma: Availability and Meaningfulness of Numbers

In trying to make products more accessible, the question of numbers quickly arises. How large should lettering be? What size button is large enough? How much pressure is too much, or not enough? In trying to make designs more accessible there are two tough principles that one has to come to grips with early.

1. You cannot make a product absolutely accessible. You can make it more accessible, but there will always be people who cannot use it.
2. Therefore... There are no magic numbers. There are no numbers to tell you that you have gone far enough and nothing more will help anyone.

At first this is hard to accept. Everyone wants a number to design to. Occasionally minimal numbers for minimal required accessibility are set, but ...

• They only can be set for a particular type of device (a phone, an elevator button, etc.).
  Such numbers are not possible for a set of general guidelines such as these, which relate to all products and all disabilities. What should be specified as the "ideal knob size" in a set of guidelines that covers wristwatches, kitchen stoves, and Walkman™ stereos?

• They only specify a minimum accessibility threshold (usually required by law or regulation).
  They always leave someone out that should be accommodated if possible in a particular product design.

The Problem with Diversity of Types and Degrees of Impairment

This latter point is the most important. A key problem in picking or setting a number is deciding who to leave out. The reason for discussing accessible design in the first place is that the standard design process currently only targets "most" of the people, and then stops. Some target number is established that is "good enough" to cover 80%, 90% or 95% of the people, and then developers end up designing to that number and stopping - even if they could just have easily gone a bit further. And it is that last phrase that is important. Since no product can be made completely accessible, a designer can't ever win completely. Tough to accept or deal with, but a fact of life. The secret, then, is to go as far as one can in making the design accessible. Setting a number as "good enough" for "most people with disabilities" and then designing to it just repeats the mistake that was made in the standard design process.

For example, to specify exactly how large lettering should be in order to be visible, you must first ask "visible to whom?" For any number you cite, there will be people who could see it if it were just a little bigger and others who would be unable to read it if you made it any smaller. There would also be some who could not see it no matter how large you made it. Thus, there is no number that will allow all people to read it. You always end up leaving some people off. The question then isn't "How large must lettering be to be accessible?" The proper question is "How large can this lettering be and still work for this product?" The decision to make it as large as practical will make the product accessible to a greater number of people. However, the decision as to the exact amount of enlargement that can be effectively used on the lettering for any given product is a decision that must be made as a part of the design process for that specific product.

Numbers Do Have their Place

This is not to say that numbers are not useful. They are essential to any design process. The numbers needed, however, are not "target" numbers or "this is now accessible" numbers, but rather numbers that a designer can use as milestones to see how changes in a design will affect users. Whenever data of this type exist or are identified they will be either included or cited in these Guidelines. An example of this is Figure O-7-a on the sensitivity of people with photosensitive epilepsy to different flicker frequencies. The chart does not give a magic frequency that would be safe (wouldn't trigger a seizure in anyone) under all conditions. It does, however, clearly indicate that avoiding 20 hz flicker by as much as practical will clearly be to the benefit of those with photosensitive epilepsy.

Occasionally, recommended "minimum" or "maximum" values do exist. Sometimes they are created as part of regulations or standards which set a baseline that everyone must comply with for some product or market. In other cases, "rule of thumb" values exist which are known or believed to cover the majority of people or situations. As the new accessibility standards for ADA compliance are finalized, for example, those that might apply to consumer products will be included in these Guidelines for reference. In all cases, however, these values should be used as milestones and not as absolute or "good enough" design targets. If it is possible to go beyond the value and create a more accessible design, then that should be considered.

The Role of These Guidelines

The role of these Guidelines, then, is more to raise the awareness and understanding of designers and to help them ask the right questions than to provide specific answers or numbers. Notwithstanding, wherever specific design ideas or "recommendable" values do exist, they are provided. When they do not, general recommendations or design ideas are provided to help designers identify areas where attention can increase accessibility. In addition, data are provided when available to help designers measure the impact of various design decisions or tradeoffs.

The Role of the Designer

In all cases, however, the exact values to use for a given product design will have to be determined by balancing the various design factors and constraints for that particular product. They cannot be dictated a priori without picking a number which will be too restrictive for some designs and unnecessarily loose for others.

Solomon's Trap

Often, initial attempts at accessible design are done piecemeal. Accessible features are added where they are obvious rather than as a result of looking at the product's overall accessibility. The result can be a design which has accessible parts, but is not as a whole accessible or usable. Access to half a product when the rest is inaccessible is of little practical use.

In some cases, inspired by a desire to address the needs of people with different disabilities, it is even possible to design some parts of a device (such as the controls) to be more accessible to one population and design another part of the product with another disability in mind. Unless the whole product is accessible to at least one of these populations no-one is served.

In most cases it is possible with careful design to create products which are simultaneously accessible to people with different impairments. However, where this is not possible, care should be taken to be sure that the entire product is accessible to those disability populations that you are able to address. Giving half a product to one disability group and the other half of the product to another is not helpful to or desired by any of the disability groups.

Resolving Conflicting Recommendations

Sometimes a solution to a problem for one type of disability may cause a new problem for a person with another type of disability. For example, those with visual impairments may be helped by replacing a visual readout with auditory output, but this would in turn cause a problem for those with hearing impairments. As such situations arise, the Guidelines will attempt to highlight them and suggest ways to avoid or minimize any potential conflicts.

At the end of most sections, a summary of the recommendations, along with examples of balanced solutions, is presented. These are not the only, and perhaps not the best, solutions. They do, however, show how multiple recommendations can be addressed even when they seem to be contradictory. They also illustrate that it is usually impossible to follow all of the recommendations simultaneously.

NOTE: The ADA guidelines are currently under development and the ANSI standards for accessibility are currently under revision. When these activities are completed, specifications for minimum levels of accessibility for some types of structures and products will be spelled out. As these minimum values are defined they will be added to these guidelines in the sections to which they apply. To avoid confusion existing and proposed standards are not included in this draft.

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SECTION 1: OUTPUT / DISPLAYS. Includes all means of presenting information to the user

Maximize the number of people who can/will ...

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O-1. Maximize the number of people who can... hear auditory output clearly enough.

Problem:

Information presented auditorially (e.g., synthesized speech, cuing and warning beeps, buzzers, tones, machine noises) may not be effectively heard.

Examples:

• Individuals who have mildly to moderately impaired hearing may not be able to discern sounds that are too low in volume.
• Individuals who have mild hearing impairments may be unable to turn the volume up sufficiently in some environments (e.g., libraries, where others would be disturbed, or in noisy environments, where even the highest volume is insufficient).
• People with moderate hearing impairments are often unable to hear sounds in higher frequencies (above 2000 Hz).
• People with hearing aids may have difficulty separating background noise from from the desired auditory information.
• People with cognitive impairments may be easily distracted by too much background noise.
• Auditory information which is short or not repeated or repeatable (e.g., a short beep or voice message) may be missed or not understood.

NOTE: Severely hearing impaired (and deaf) people cannot use audio output at all. See O-2 for guideline to address this problem.

Design Options and Ideas to Consider:

• Providing a volume adjustment, preferably using a visual volume indicator. Sound should be intelligible (undistorted) throughout the volume range.
• Making audio output (or volume range if adjustable) as loud as practical.
• Using sounds which have strong mid-low frequency components (500 - 3000 Hz).
• Providing a headphone jack to enable a person with impaired hearing to listen at high volume without disturbing others, to enable such a person to effectively isolate themselves from background noise, and to facilitate use of neck loops and special amplifiers (see additional information below).
• Providing a separate volume control for the headphone jack so that people without hearing impairments can listen as well (at standard listening levels).
• When a headphone jack is not possible:
  • placing the sound source on the front of the device and away from loud mechanisms would facilitate hearing.
  • locating the speaker on the front of the device would also facilitate use of a small microphone and amplifier to pick up and present the information (via speaker, neckloop or vibrator).
• Facilitating the direct use of the telecoil in hearing aids by incorporating a built-in inductive loop in your product (e.g., in telephone receiver's earpiece).
• Reducing the amount of unmeaningful sound produced by the product (i.e., background noise).
• Presenting auditory information continuously or periodically until the desired message is confirmed or acted upon. Spoken messages could automatically repeat or have a mechanism for the user to ask for them to be repeated.

Additional Information:

• An adjustable and fairly loud volume is particularly helpful to aging individuals and others with mild hearing impairments who do not normally carry or use hearing aids or other sound amplification devices. (Note that many such people do not wish to acknowledge their hearing loss by wearing aids.)
• Visual indication of the volume setting is important, as individuals with hearing impairments often do not know or realize the volume level is set painfully high for others. Simple strategies include a painted and/or tactile dot or arrow on a control dial, a sliding bar volume control, numbers or graphics (on a thumbwheel dial), or an on-screen bar graph volume indicator (see examples below).
• Loss of hearing associated with age generally begins with the inability to hear high frequencies. Thus, use of lower frequencies will be particularly helpful to older people.
• For alerting devices the use of two or more spectral components in the 500 - 4500 Hz range is recommended based on ringer studies . Others suggest limiting the upper frequency to 3000 Hz to better accommodate people with mid-high frequency loss.
• When using voice output, male voices are usually preferable to female voices because of their lower pitch. Consonants which are particularly easy to hear in the male speech patterns are "m" and "n."
• The use of sufficient volume and low frequency are particularly critical for alarms.
  (See S-1 for guideline to specifically address this problem.)
• For some products it may be feasible to have adjustable frequency of auditory output.
• A (front mounted) headphone jack allows individuals with hearing impairments to carry a pair of headphones or headphones equipped with a small, battery-operated amplifier to provide the necessary sound levels.
• Headphone jacks come in two sizes. The commonly used ones are 1/4" and 1/8 ". Because both are so commonly used, most headphones come with an adaptor which allows them to work with both jack sizes. As a result, either size is generally acceptable. The larger size jack is slightly easier to handle and more rugged but the smaller size is becoming the more common size due to miniaturization of equipment.
• The headphone jack can be used to connect an inductive neckloop (loop which is worn around the neck and provides direct inductive coupling with the t-coil in a hearing aid).
• Headphone jacks are also appreciated by non-hearing-impaired people and people with certain types of learning disabilities where use of a headphone is desirable for privacy or in both noisy and quiet environments (e.g., factory, office, or library). A separate volume control for the headphones is also useful when others would like to listen to the same output (via speakers) at a lower volume.

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Figure O-1-a: A neck ring or ear loop can be plugged into a headphone jack on an audio source and provide direct inductive coupling between the audio source and a special induction coil on a person's hearing aid. This cuts out background noise that would be picked up by the hearing aid's microphone and provides clearer reception of the audio signal.

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Figure O-1-b: A headphone jack permits the connection of headphones, neck/ear loops, amplifiers or sound indication lights.

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Figure O-1-c: Speaker near edge and away from unwanted noise sources allows use of microphone to pick up sounds and relay on to an amplifier and speaker or neckloop. (Not as good as headphone jack.)

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On-screen bar graph (need non-visual method as well); Visual (and tactile) dot; Sliding Control with Reference (Not as good for people who are blind).

Figure O-1-d: Provision of a visual indicator of volume level is useful so that people with hearing impairments can better judge the impact of volume on others in the environment.

Figure O-1-e
Hearing Loss as a Function of Age

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Figure O-1-f
Hearing Loss for Different Frequencies as a Function of Age

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Figure O-1-g
Recommended Frequency for Altering Devices

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O-2. Maximize the number of people who will ... not miss important information if they can't hear.

Problem:

Audio output (e.g., synthesized speech, cuing and warning beeps, buzzers, tones) may not be heard at all or may be insufficient for effectively communicating information.

Examples:

• Individuals who are severely hearing-impaired or deaf may not hear audio output, even at high volume and low frequencies.
• Individuals with language or cognitive impairments may not be able to respond to information given only in auditory form. (This may also be true if the language used is not the primary language of the individual.)
• Individuals who are deaf-blind may not hear audio output.
• Individuals with standard hearing must sometimes use products in environments where the sound must be turned off (libraries) or where the environment is too noisy to hear any sound output reliably.

Design Options and Ideas to Consider:

• Providing all important auditory information in visual form as well (or having it available). This includes any speech output as well as auditory cues and warnings.
• Providing a tactile indication of auditory information.
• Facilitating the connection or use of tactile aids.
• Providing an optional remote audio/visual or tactile indicator.

Additional Information:

• It is understood that those products designed solely for the purpose of providing audio output (e.g., radios, stereos, CD and casette players) will not generally be useful to severely hearing-impaired/deaf people without special external adaptations. Therefore, it is not intended that this guideline should apply to such products.
• Some methods for accompanying auditory cues and warnings with a visual indication would be to blink all or part of the display screen or any existing light(s) on the product. (Avoid high frequency flicker - over 2-3 Hz; see O-7.)
• If it is not possible to provide a redundant visual cue for the auditory information, a headphone jack would allow the user to plug in a small LED or light that would provide a visual flicker whenever sound was emitted from the product's speaker. (For deaf-blind users a small vibrator could be used.) This would be sufficient only to indicate that a sound had occurred, not the character (and therefore possibly the meaning) of the sound if frequency or timbre were used to convey information.
• When a headphone jack is not provided, the placement of the sound source near a quiet location and with the speakers facing the user facilitates the use of a small microphone and amplifier with a small LED or tactile stimulator (as well as a speaker or neckloop - see O­1).
• Use of a remote audio/visual or tactile indicator (e.g., to indicate that the washer or dryer in the basement is done) is useful to all. For example, a small unit might come with an appliance (like a stove or dryer) which could be carried around with a person (who will not be in earshot of the appliance) and beep, buzz, or vibrate when the appliance is "done." Alternately, the remote indicator could be a small device which plugs into the wall and is triggered by signals sent over the house wiring by the appliance (e.g. dryer) to indicate that it is done.
• Any voice output from computers, TV's and other products which is not also available as printed text on the screen or product should be available (optionally) through captions on the display screen. External captioning devices can be connected after the fact to some devices, but they are expensive and require that the user carry the devices with them to connect to the products as they encounter them. They are also practical - or even possible with public-use products. Built in captioning facilities are usually very inexpensive and effective. NOTE: After July 26, 1993 all televisions will be required to include built-in caption decoding circuitry.

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Figure O-2-a: LED next to speaker gives redundant visual indication of all auditory information.

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Figure O-2-b: A baby monitor from Fisher-Price provides a visual indication of the loudness of the sounds from the baby's room. [ It is advertised as being useful "even if you're surrounded by other noises, the TV, the phone, the vacuum, the dishwasher..." ]

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Figure O-2-c: A headphone jack permits the connection of visual and tactile indicators. It would also allow the connection of remote alerting devices which could be carried or positioned in other places in the house.

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Figure O-2-d: A visual indication of computer hard disk activity provides the same information to a person who is deaf that the disk noise provides to those who can hear. This feature is also useful to hearing users when the disk drive is silent or there is background noise.

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O-3. Maximize the number of people who will ... have line of sight to visual output and can reach printed output.

Problem:

Visual displays or printouts may be unreadable due to their placement.

Examples:

• Individuals who are in a wheelchair or who are extremely short may be unable to read displayed information due to the physical placement or angle of the display screen.
• Individuals in wheelchairs, with missing or paralyzed arms, or with ability to move limited by cerebral palsy or disease (e.g., severe arthritis, MS, ALS, muscular dystrophy) may be unable to reach printed output (e.g., receipts produced by an Automatic Teller Machine) due to printer placement.

Design Options and Ideas to Consider:

• Locating display screens so they are readable from varying heights, including a wheelchair (see I-1 for specific anthropomorphic data; see O-4 regarding image height).
• Locating printed output within easy reach of those who are in wheelchairs.
• Facilitating manipulation of printouts by "reaching and grasping" aids.
• Providing redundant audio output in addition to visual display if the visual display cannot be made physically accessible to an individual in a wheelchair. (See O­5.)

Additional Information:

• "Reaching and grasping" aids include: reachers, artificial hands or hooks, and special mouthsticks with clasps attached. See figure M-1-f.
• For reach and eye level anthropometrics see Figures I-1-a.

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O-4. Maximize the number of people who can ... see visual output clearly enough.

Problem:

Visual output (e.g., information presented on screens, paper printouts, cuing and warning lights or dials) may not be effectively seen.

Examples:

• Individuals who are visually impaired may not be able to see output that is too small.
• Those who are visually impaired may have difficulty discerning complex typefaces or graphics.
• Individuals who are color blind may not be able to differentiate between certain color pairs.
• People with poor vision have more difficulty seeing letters/pictures against a background of similar hue or intensity (low contrast).
• Individuals with visual impairments may be much more sensitive to glare.
• Those who have visual impairments may not be able to see detail in low lighting.
• Some people with severe lack of head control (e.g., cerebral palsy) may not be able to maintain continuous eye contact with a display, and therefore these individuals may miss portions of dynamic (i.e., moving, changing) displays.

NOTE: See O-5 for guidelines for people who cannot use visual output at all. See O-6 for problems in understanding displayed output.

Design Options and Ideas to Consider:

• Making letters and symbols on visual output as large as possible/practical.
• Using upper and lowercase type to maximize readability
• Making sure that...
  • leading (space between the letters of a word)
  • the space between lines
  • the distance between messages
  • sufficient that the letters and messages to stand out distinctly from each other.
• Providing adjustable display image size.
• Providing a video jack for attaching larger-image displays or utilizing special assistive devices (e.g., electronic magnifiers; see additional information below).
• Using high contrast between text or graphics and background.
• Keeping letters and symbols on visual output as simple as possible; using sans serif typefaces for non text lettering (e.g., labels, dials, displays) (see D-1)
• Using only black and white or using colors that vary in intensity so that the color itself carries no information.
• Providing adjustable color selection (hue and/or intensity).
• Replacing or supplementing color coding with different shape or relative position coding.
• Providing contrast and/or brightness adjustment.
• Minimizing glare (e.g., by employing filtering devices on display screens and/or avoiding shiny surfaces and finishes).
• Providing the best possible lighting for displays or areas containing instrumentation. (good even illumination without hot spots and brighter than background illumination)
• Providing adjustable speed for dynamic displays (so they can be slowed down for those who lack motor control).
• Avoiding use of the color blue to convey important information. (see below)
• Increasing contrast on LCD displays by allowing user to adjust viewing angle.

Additional Information:

• Contrast controls are important even on monochrome monitors.
• Colors that are of sufficiently different intensity (e.g., light yellow vs. dark red) can be distinguishable as different shades even to a color blind individual.
• The use of glass, chrome and smooth plastics increase the chance for creating glare.
• The Illuminating Engineering Society recommends very strong task light to aid in seeing for performance of visual tasks of low contrast or very small size (e.g., placing a needle on a record, sewing). If the products are too heavy or cumbersome to bring to a bright light, easily attachable lights positioned so they do not produce glare should be used.
• Reduce reflectivity of display screen (quarter-wave coatings or etched green surfaces preferred to micromesh, polarized or tinted filters).
• Yellowing of the cornea as we age interferes with the passage of blue light and can cause confusions between some shades of blue, green, and violet.

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Figure O-4-a: Ability to tolerate glare decreases sharply as a function of age as shown above. Data are based on a 1° glare source size and a background luminance of 1.6 fl. (Source: Bennett, 1977a, fig. 1.)

[Insert Chart Here] D

Figure O-4-b: By avoiding lines of confusion in the chromatic chart above one can circumvent problems with the major types of color blindness. For maximum visibility there should also be a high contrast between the figure (text) and background.

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O-5. Maximize the number of people who will... not miss important information if they can't see.

Problem:

Visual output (e.g., information presented on screens, paper printouts, cuing and warning lights, and dials) may not be seen at all by some users.

Examples:

• Individuals who are severely visually impaired or blind may not be able to see visual output, even when magnified and clarified (as recommended in O­4).
• Individuals who cannot read may be unable to use visually presented text.
• Individuals who are deaf and blind may only be able to perceive tactile output.
• Individuals who do not have any visual impairment may miss warnings, cues, or other information if it is presented only in visual form while their attention is diverted.

Design Options and Ideas to Consider:

• Providing all important visual information (redundantly) in audio and/or tactile form.
• Accompanying visual cues and warnings by a sound, one component of which is of a mid-low frequency (500-3000 Hz). (See O- 1.)
• Making information which is visually displayed (both text and graphics) also available electronically at an external connection point (standard or special port) to facilitate the use of special assistive devices (e.g., voice synthesizers, braille printers). Preferably the information would be available in an industry or company standard format.

Additional Information:

• It is understood that those products designed solely for the purpose of providing visual output (e.g., slide projectors, cameras) will not generally be useful to severely visually-impaired/blind people without special external adaptations. Therefore, it is not intended that this guideline should necessarily be applied to such products. It is, however, very useful for people who are blind to be able to use a copy machine or word processor.
• Note that audio signals which are redundant with visual cues can also benefit the general user, especially for products which may be in use some distance from the user (e.g., in the next room) or where the user's attention may be diverted.
• Some (but not all) people with learning disabilities could benefit from simultaneously seeing and hearing information.
• All visually displayed information could be provided via voice synthesizer. The cost for voice output is dropping rapidly. A small button could be used to turn the voice on or off. (This can be useful to people who are blind, have low vision, or have difficulty reading the display. It could also provide cuing or instructions which would be more than could conveniently be displayed on a control panel or small display.)
• The external connector could be a standard parallel, serial, or other I/O port. The data rate of the port should be appropriate for the amount of data that needs to be transmitted. Products with small amounts of displayed information could use a low bandwidth port.
• Serial RS-232 provides a very common, low cost, standard connection format. Serial data can also be sent via infra-red link. (see next)
• An inexpensive and unobtrusive approach would be to provide a small infra-red LED which would transmit the displayed information via a pulse train of infra-red light. Information could be sent in ASCII which could be picked up by a device which would translate the information into voice or braille. This approach allow individuals to receive information from the product without the user having to actually connect a special aid to the product. (which is physically difficult for individuals with physical limitations and requires people with blindness to locate the proper connection point on the product). This approach can be very inexpensive to implement but would require that the user have and carry a receiving device. This would be reasonable if the technique were used in a widespread manner. Direct accessibility of the products without an external device would, however, be superior. (See also I-7 for infra-red coupling in opposite direction)
• Text information could be provided in ASCII. Graphics information could be provided via a word description, a character listing (for character-based screen displays), or a bit image. (See D­1.)
• When providing information via text to an auxiliary port there are at least two different strategies that could be used. One would be to provide the exact information that is on the display screen and let the user maneuver about on it (the screen text image) using their access device. The second approach would be to send out different (from that displayed on the screen) but equivalent ASCII text that would provide the same information as presented on the screen but in a format which was more conducive to audio presentation. This would allow the use of fuller English sentences and the presentation of information in a way that would be more conducive to auditory memory. It would also allow for the use of a very simple device that would convert IR to text to speech (or Braille).
• Visual cues and warnings might be accompanied by a distinct vibration for deaf users who may not be looking at the display and would miss the cuing beep as well as for deaf-blind users. See S-1.

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Figure O-5-a: As the cost for voice synthesis continues to drop, a "Read Display" button could be included in appliances that have visual displays to allow them to be more easily and accurately read by people with visual impairments (low vision or blindness). For displays that are set (timers, etc.) the button should be pushable (for a quick read) or lockable (so that it would read out continually as it was adjusted).

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Figure O-5-b: If direct accessibility cannot be built in for some reason, an external connector would allow individuals with special interface devices to connect them. A relatively low cost and vandal resistant connector could be provided via an infra-red bidirectional link. Individuals who are blind or unable to read the displayed information could then use an assistive device and have information presented in auditory or tactile (braille) form.

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O-6. Maximize the number of people who can ... understand the output (visual, auditory, other).

Problem:

Visual and/or auditory output may be confusing or hard to understand.

Examples:

• Some people with specific learning disabilities or with reduced or impaired cognitive abilities:
  • are easily confused by complex screen layouts (e.g., multiple "windows" of information).
  • have difficulty understanding complex or sophisticated verbal (printed or spoken) output.
  • have a short attention span, and are easily distracted when reviewing a screen display.
• For many individuals who are deaf, as well as many other U.S. citizens, English is a second language and not well understood.

Design Options and Ideas to Consider:

• Using simple screen layouts, or providing the user with the option to look at one thing at a time.
• Shortening menus.
• Hiding (or layering) seldom used commands or information.
• Keeping language as simple as possible.
• Accompanying words with pictures or icons. (Note, however, that the use of graphics may present more difficulty for people who are blind. See O-5.)
• Using Arabic rather than Roman numerals (e.g., use 1, 2, 3 instead of I, II, III).
• Using attention-attracting (e.g. underlining, boldfacing) and grouping techniques (e.g., putting a box around things or color blocking).
• Highlighting key information.
• Putting most important information at the beginning of written text (but not spoken).
• Providing an attention-getting sound or words before audio presentation.
• Keeping auditory presentations short.
• Having auto-repeat or a means to repeat auditory messages.
• Presenting information in as many (redundant) forms as possible/practical (i.e., visual, audio and tactile) or providing as many display options as possible.
• Providing digital readouts for product generated numbers where the numeric or precise value is important. Providing dials or bar graphs where qualitative information is more important (e.g. half full, full etc). (See I-4 and I-6 for Input/Controls.)

Additional Information:

• To simplify language, try to have each sentence contain only one clause. Look for an easier way to phrase sentences with more than one verb. Favor active and affirmative statements over passive or negative statements (e.g., "The red button controls the volume" is more direct than "The volume is controlled by the red button"). Avoid abbreviations (e.g., use stop, exit, or escape rather than esc).
• Another easy way of simplifying screen layout is to break up large amounts of text by using double spacing, lots of blank space, or breaking text into smaller units (paragraphs). If feasible, allow each section to be called up individually, letting the user control the reading rate.

[illustration will go here when ready] D

Figure O-6-a: Displays that use shorter sentences with careful use of white space, grouping of items, and a logical layout are easier to understand or interpret than displays that have too much text that is laid out in one font and block format.

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O-7. Maximize the number of people who can ... view the output display without triggering a seizure.

Problem:

Individuals with seizure sensitivities (e.g., epilepsy) may be affected by screen cursor or display update frequencies, increasing the chance of a seizure while working on or near a display screen.

Design Options and Ideas to Consider:

• Avoiding screen refresh or update flicker or flashing frequencies which are most likely to trigger seizure activity (see chart below).

Additional Information:

• Somewhere between 1 in 25,000 and 1 in 10,000 are affected by photosensitive epilepsy (i.e., 25,000 - 100,000 people).
• The flash rates most likely to induce convulsions have been found to be between 10 and 50 hertz with a peak around 20 hertz. We recommend keeping away from flicker rates in the 5 to 50 hertz range. * (See chart below for example of the relative sensitivity of individuals to different frequencies.)
• Sensitivity to flicker increases with the intensity of the light and the portion of the person's visual field which is affected (e.g., a flickering or flashing screen is much worse than a small line cursor). Focusing attention on a flashing object would also increase its effect.
• To avoid screen flicker use 80-100 Hz refresh rate with decay time approx. 10 ms to 10% luminance level.

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Figure O-7-a: Percent of photosensitive patients in whom a photoconvulsive response was elicited by a 2 second train of flashes with eyes open and closed. As can be seen, the greatest sensitivity is at 20 Hz with a steep drop off at higher and lower frequencies. (Jeavons, P.M., and Harding, G.F.A. 1975)

*Recommendation added after original 1992 publication date.

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SECTION 2: INPUT / CONTROLS. Includes keyboards and all other means of communicating to the device

Maximize the number of people who can ...

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I-1. Maximize the number of people who can ... reach the controls.

Problem:

Controls, keyboards, etc. may be unreachable or unusable.

Examples:

• Individuals who use a wheelchair, who are very weak or who are extremely short may be unable to reach some controls, keypads, etc., well enough to use them.
• Individuals with poor motor control may be able to reach the controls, but may find them too small or close together to accurately operate the proper knobs, buttons, etc.
• Individuals with severe weakness may be able to reach the controls, but may find the act of reaching or holding position in order to manipulate the controls too tiring.

Design Options and Ideas to Consider:

• Locating controls, keyboards, etc. so they are within easy reach of those who are in wheelchairs or have limited reach.
• Locating controls so that the user can reach and use them with the least change in body position.
• Locating controls which must be constantly used in the closest positions possible and where there is wrist or arm support.
• Providing a (redundant) speech recognition input option.
• Offering remote controls (wired, wireless or bus operated).

Additional Information:

• Accessibility to a control becomes less critical if the control is for an adjustment that is only occasionally used or used only at setup time.
• Avoid placement that requires the user to lean around the side or back of the device to see or operate the controls.
• Voice controls (i.e., controls employing speech recognition) may be inaccessible for those with speech impairments. Therefore, if voice control is the only means provided, alternative control/input methods will need to be available for these people. (See I- 7.)
• Locate controls 36-48" above floor.
• Controls that are located too far apart may require that users reposition themselves or their wheelchairs each time they move between controls.

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Figure I-1-a: Eye level anthropometrics. (Jones M.L. 1978)

Note: These are for an "average" woman in a wheelchair. Children and people with dwarfism would not have this reach or height. Also people with weakness caused by ALS, MS, MD and other impairments would have more limited reach.

[insert full page graphic here] D

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Figure I-1-b: Normal placement of stove controls poses serious reach and safety problems for individuals who are very short or in a wheelchair.

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I-2. Maximize the number of people who can ... find the individual controls/keys if they can't see them.

Problem:

People with visual impairments may be unable to find controls.

Examples:

• Individuals who are severely visually impaired may be unable to locate controls tactilely because they are on a flat membrane or glass panel (e.g., calculators, microwave ovens) or because they are placed too close together or in a complicated arrangement.
• Individuals who have diabetes may have both visual impairments and failing sensation in fingertips, making it hard to locate controls that have only subtle tactile cues.

Design Options and Ideas to Consider:

• Varying the size of controls (also texture or shape) with the most important being larger to facilitate their location and identification.
• Providing controls whose shapes are associated with their functions.
• Providing sufficient space between controls for easy tactile location and identification as well as easier labeling (large print or braille).
• Locating controls adjacent to what they control.
• Making layout of controls logical and easy to understand, to facilitate tactile identification (e.g., stove burner controls in corresponding locations to actual burners).
• Providing a raised lip or ridge around flat (membrane or glass) panel buttons .
• Providing a (redundant) speech recognition input option.

Additional Information:

• Diameter changes of at least 3/8" and thickness changes of at least 1/32" are more readily detectable by people who are blind.
• Vertically arranged controls may be easier for people who are blind to locate than horizontally arranged controls.
• Voice controls (i.e., controls employing speech recognition) may be inaccessible for those with speech impairments. Therefore, if voice control is the only means provided, alternative control/input methods will need to be available for these people. (See I-7.)

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D Keypad on which edge views below are based.

Figure I-2-a: The shape of a key or button can have a significant effect on people's ability to accurately locate (and operate) it.

A flat membrane or glass keypad provides no tactile indication as to where the keys are, even if you memorize the arrangement.

Providing a slight raised lip around the keys allows their location to be discerned easily by touch. The ridge around the key also helps prevent slipping off of the key when using a mouthstick, reacher, etc. to press the keys.

Raised bumps are tactilely discernable but it is harder to press the key without slipping off, particularly if you are using a mouthstick, reacher or other manipulative aid.

Raised keys with indents provide better feedback then just indents (as in example above) especially if the keys have different shapes or textures which correspond to their function.

Using indentations or hollows on the touchpad provides most of the advantage of ridges but is easier to clean. Hollows can be the same size as the key or of a consistent small circular size centered on the keys. Shallow edges such as those on the left button are harder to sense with fingers than the sharper curve of the middle button.

INSTRUCTIONS: For each keyboard below,visually locate the key on the right hand keyboard that corresponds to the marked key on the left. Note the increase in speed and accuracy when landmarks (nibs or breaks in the key patterns) are provided.

First keyboard: No landmarks except edges of keyboard.

Second keyboard: Nibs on keys used as landmarks.

Third keyboard: No landmarks

Fourth keyboard: Spacing used to provide landmarks.

Fifth keyboard: No landmarks

Sixth keyboard: Color or shading used to create landmarks.

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Figure I-2-b: Quick self-demonstration of the impact of landmarks on key-finding by people who cannot see labels on a key due to blindness or very low vision.

[Insert Blurred TV Control Panel Photo Here]
(Photo courtesy of John Ward) D

Figure I-2-c: Low Vision (blurred) View of a Television Control Panel

What button would you push to change the channel?

This television's control panel is undecipherable to people with low vision due to the layout, positioning of the channel vs volume controls (the buttons next to the channel display do not control the channel selection... they are the volume control buttons.), the use of abbreviations, the low contrast of the on/off switch and lack of a door to cover up the seldom used and confusing setup controls at the bottom. See Figure I-6-a for a drawing of this control panel (Answer: the channel control buttons are the two white triangles in the upper right, next to the on/off switch.)

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I-3. Maximize the number of people who can ... read the labels on the controls/keys.

Problem:

Labels on controls, keys, etc. are difficult or impossible to see due to their size, color or location.

Examples:

• Individuals with low vision may have difficulty identifying controls or keys on a keyboard because the label lettering is too small and/or because the contrast between letters/graphics and background is poor.
• Individuals with color blindness may have difficulty distinguishing controls which are color-coded, or which use certain pairs of colors for labels and background.
• Individuals with physical impairments may have difficulty reading labels on the sides or backs of objects.
• Individuals who are blind may not be able to see printed labels at all.

Design Options and Ideas to Consider:

• Making lettering used for labels as large as possible/practical.
• Making sure that...
  • leading (space between the letters of a word)
  • the space between lines
  • the distance between labels
  is sufficient that the letters and labels to stand out distinctly from each other.
• Placing important labels or instructions on front or easily accessible side of large or stationary devices, where they can be read from wheelchairs.
• Using Sans Serif fonts for non-text lettering (e.g., labels, dials).
• Using high contrast between letters/graphics and background.
• Providing sufficient illumination of controls and instructions
• Supplementing color coding with use of different button/key shape or letter/graphic labels.
• Providing color choices for color coded buttons.
• Providing tactile labels.
• Avoiding use of blues, greens, and violets to encode information (since the yellowing of the cornea can cause confusions between some shades of these colors).
• Use of easily interchangeable keycaps to allow replacement with special or optional keycaps.
• Arranging controls in groupings which facilitate tactile identification (e.g., using small groups of keys that are separated from the other keys, or placing frequently used keys near tactile landmarks such as along the edges of a keyboard).
• Using established layouts for keyboards (e.g., typewriter, adding machine, phone).
• Using voice output to "speak" the names of keys or buttons as they are pressed. (This capability would need to be turned on and off as needed.)
• If a flat membrane panel cannot be avoided, provide a stick-on tactile overlay that provide tactile demarcation of the key locations and functions.
• See O-4 and O-6 for related guidelines for output/displays.

Additional Information:

• Lettering which uses most of the key or button surface facilitates readability.
• Use of bold sans serif typeface is easier for those with low vision to read.
• Light gray on white and other similar stylish but low contrast combinations should be avoided.
• One rule of thumb is that no key should be more than one key away from a tactile landmark. (e.g. a corner, a uniquely shaped key, a key with a nib, or one of the eight "home" keys on a keyboard)
• A common approach for providing tactile markings on keyboards is to put nibs on the front edge of the F and J or D and K keys as well as on the 5 key on a numeric keypad. This enables users to operate the keys by "touch."
• Tactile,and/or large print labels could be made available as stick-on options. These could be raised lettering or braille. Optional key caps might also be provided for keyboards or buttons. These caps could have raised lettering or transparent braille labels.
• Raised lettering should be at least 1/32".

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I-4. Maximize the number of people who can ... determine the status or setting of the controls if they can't see them.

Problem:

Determination of control status or setting may depend solely on vision.

Example:

• Individuals with visual impairments may be unable to see a control setting or on/off indicator (e.g., where a dial is set, whether a button is pushed in, whether a light is on, flashing or off, or what a numeric setting on a visual display reads).

Design Options and Ideas to Consider:

• Providing multi-sensory indication of the separate divisions, positions and levels of the controls (e.g. use of detents or clicks to indicate center position or increments, raised lines, etc).
• Using absolute reference controls (e.g., pointers) rather than relative controls (e.g., pushbuttons to increase/decrease, or round, unmarked knobs).
• Using moving pointers with stationary scales.
• Providing multi-sensory indications of control status (e.g., in addition to a status light indicating "on," or providing an intermittent audible tone and/or tactilely discernable vibration).
• Using direct keypad input.
• Providing speech output to read or confirm the setting.
• See O-3, O-4, and O-5 for design options covering visual displays.

Additional Information:

• Absolute reference controls (such as knobs with pointers) allow the user to determine their settings by directly sensing the control itself. Relative reference controls (like up/down volume control buttons, or the dial on a radio) require the user to view (or listen to) some other display while operating the control. Relative reference controls are more difficult cognitively and sensorially.
• Moving pointers and stationary scales (e.g., rotating pointer with numbers on the panel) are better than moving scales and a stationary pointer (e.g., rotating knob with numbers on the knob). A user who is blind or has low vision can use knob (pointer) position to indicate setting. People with cognitive impairments can remember knob orientation or scale position rather than dealing with scale readings. It is also easier to attach large print, raised letter or braille labels to a stationary scale. Scales placed directly on a rotating knob are also mostly sideways or upside down.
• One technique for providing tactile indication of the setting would be the use of detents, notches, etc. These are best used with an absolute pointer of some type and a clear tactile indication of the minimum and maximum settings, as well as what values those settings may represent. (Two degrees of detents to indicate large and small divisions on the scale may also be used to provide more information.)
• Auditory clicks or beeps can indicate positions on a control but are not as effective as an auditory/tactile click for people with hearing impairments or for noisy environments.
• Sliding controls are harder for blind users to quickly read than rotating controls shaped like a pointer. To determine the setting of a sliding control the person who is blind must feel the control knob as well as both ends of its travel path and then tactilely estimate the position of the knob relative to the two ends.
• Pointers on a knob can take many forms but a pointer knob with contrast between the pointer and the background provides maximal visual and tactile feedback as to its setting.
• For many types of input, direct keyboard or numeric keypad entry may be better than dials, knobs, etc.

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Figure I-4-a: The design of a knob can greatly affect its usability by people with low vision or blindness. D

		Side view
No non-visual indication of setting. If vision blurred you cannot tell setting . Difficult to put large print or braille labels on knob (Also harder to grasp and requires twisting motion)	Highly visible raised pointer Instant tactile indication of orientation allows setting to be read even if user is blind. Easy to put larger print or braille labels on back panel. Use of detents (large and small) can facilitate inter-numeral settings. Black base disk provides high contrast and helps in control location/orientation on panel. (Design is also easy to grasp and can be turned by pushing the point around - no twisting if the knob turns freely enough)

FOR EXAMPLE: What are the settings of the knobs below?

Figure I-4-b: Knob design can have substantial effect on usability by people who are blind.

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POOR: round smooth knob; no tactile orientation cue.

BETTER: has tactile orientation cue but user has to feel around to find it.

BETTER: orientation cue is less ambiguous. However the user must still feel the ends to be sure which is the pointer end.

BEST: has tactile orientation cue which is unambiguous and can be felt immediately upon grasping knob.

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Figure I-4-c: Sliding controls can be read but are more difficult since the person must find the slider and both ends of the range and then judge the ratio. Raised numbers would help.

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Figure I-4-d: Keypads allow direct and accurate setting of controls even if the person has no sight. However, this type of input is usually used with a digital display which would be inaccessible without a voice output option. Large high contrast numbers are helpful for low vision. A standard keypad layout is important.

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I-5. Maximize the number of people who can ... physically operate controls and other input mechanisms.

Problem:

Controls (or other input mechanisms) may be difficult or impossible for those with physical disabilities to operate effectively.

Examples:

• People with severe weakness may be unable to operate controls at all, or may have great difficulty performing constant, uninterrupted input.
• People with only one arm or without arms (but utilizing assistive devices such as headsticks or mouthsticks) may not be able to activate multiple controls or keys at the same time.
• People with artificial hands or reaching aids may have difficulty grasping small knobs or operating knobs or switches which require much force.
• People with poor coordination or impaired muscular control have slower or irregular reaction times, making time-dependent input unreliable.
• People lacking fine movement control may be unable to operate controls requiring accuracy (e.g. a mouse or joystick) or twisting or complex motions.
• People with limited movement control (including tremor, incoordination, or those using headsticks or mouthsticks) can inadvertently bump extra controls on their way to a nearby desired control.

Design Options and Ideas to Consider:

• Minimizing the need for strength by minimizing force required as much as possible or by providing adjustable force on mechanical controls.
• If stiff resistance is provided to prevent accidental activation it could drop off after activation. Other non-strength related safety interlocks could also be considered.
• Spacing the controls out to provide a guard space between controls. This also leaves room for adaptations such as attaching levers to hard to turn knobs or room to replace knobs with larger, easier to turn knobs or cranks.
• Minimizing or providing alternatives to performing constant, uninterrupted actions (e.g., button locks or push on - push off buttons would eliminate the need to press some buttons continuously).
• Where simultaneous actions are required (e.g., pressing shift or control key while typing another key) provide an alternative method to achieve the same result that does not require simultaneous actions (e.g., sequential option as in StickyKeys - see below).
• Providing for operation with left or right hand.
• Using concave and/or non-slip buttons, which are easier to use with mouthsticks or headsticks. On flat membrane keypads, provide a ridge around buttons.
• If product requires a quick response (i.e., a reaction time of less than 5 seconds, or release of a key or button in less than 1.5 seconds), allow the user to adjust the time interval or to have a non-time-dependent alternate input method.
• If product requires fine motor control, then provide an alternate mechanism for achieving the same objectives that does not require fine motor control (e.g., on a mouse-based computer, provide a way to achieve mouse actions from the keyboard).
• Avoiding controls that require twisting or complex motions (e.g., push and turn). (Note: there are rotating knobs that do not require twisting.)
• Spacing, positioning and sizing controls to allow manipulation by individuals with poor motor control or arthritis.
• Where many keys must be located in close proximity, providing an option that delays the acceptance of input for a preset, adjustable amount of time (i.e., the key must be held down for the preset amount of time before it is accepted) helps some users who would otherwise bump and activate keys on the way to pressing their desired key. Note: this option must be difficult to accidentally invoke and be provided on request only, as it can have the effect of making the keyboard appear to be "broken" to naive users.
• Making keyboards adjustable from horizontal. (0-15 degrees is standard.)
• Providing an optional keyguard or keyguard mounting for keyboards.
• Providing optional (redundant) voice control.
• Providing textured controls (avoid slippery surfaces/controls).

Additional Information:

• Accessibility is somewhat less important for those input devices and controls needed only for periodic adjustment, maintenance, set-up, or materials replacement aspects of the product (e.g., changing ribbons or paper). Where possible, however, it is still recommended.
• In some instances the force required to operate controls gives feedback to the user (e.g., a typist knows when a key is pushed by the force that the key generates against the finger). In such cases, this feedback should not be removed entirely or substitute cues provided when force requirements are minimized.
• Use of a keypad is a common technique for providing an alternate mechanism to fine motor control. "MouseKeys," which allows the user to drive a mouse cursor around the screen (or move it one pixel at a time) by using the keypad on a keyboard, is an example of this.
• StickyKeys is a function which when built into a keyboard allows users to operate all of the modifier keys (Shift, Control, etc.) with only a single finger, mouthstick or headstick. Once it is turned on, you can press the shift key and release it, THEN press any other key to get the shifted value of the key. Pressing the shift key twice "locks" the shift key down until it is pressed a third time. When StickyKeys is turned off it does not affect normal typing in any way. As a result it can be installed on standard public access keyboards and remain unnoticed until needed by a user with a disability (who can quickly invoke it by tapping the shift key 5 times in a row to wake it up). StickyKeys (as well as MouseKeys) is provided as a standard feature on all Macintosh and Apple II computers shipped. Microsoft and IBM also provide StickyKeys (as well as MouseKeys and other keyboard enhancements) as a part of an optional access package of extensions for Windows 3.0 and DOS respectively.
• Key design: 25-150 grams of force, preferably adjustable with tactile and audible feedback, 2-5 mm of travel, 12-15 mm surface dimensions, 18-20 mm spacing.
• Keyguards for standard computer keyboards are available from several suppliers.
• Adjustments of time interval should have five or more increments which vary the time interval.
• One alternative to time dependent input methods is the use of a keypad which allows direct entry of the desired setting.
• Larger controls are, in general, easier to operate. Large round controls that have good traction surfaces and turn easily can often be operated with the side of one's hand.
• If you can attach a post to a twist knob it becomes a crank and can be operated more easily and without a twisting motion. If the knob is large, a post might be positionable within the circumference of the knob. For smaller knobs, an optional extension rod would provide additional leverage if there is enough room between knobs.

Comments on some common types of controls: (controls towards top of list are generally more accessible)

• Rocker switches (concave)
  + good example of push-push switch
  + good feedback for visually impaired users
• Controls all operable from a single keyboard/keypad
  + good, especially if keyboard is repositionable
• Pushbutton controls
  + good for head/mouthstick operation (preferably concave button requiring less than 100 grams of pressure)
• Double-acting pushbutton controls
  + Push-push controls better than push-pull
  - difficult for blind users to tell status unless button locks in
• Up/down (integrating) control buttons (e.g., volume control buttons)
  + requires little manipulation
  + best if light action and concave button
  - requires monitoring of some other output to determine setting

  - hard for visually impaired users if setting values are displayed visually
  - hard for deaf or hard of hearing users to judge volume (to others)

  - requires person be able to hold hand in place
  - requires timing/reaction time
• Sliding or edge-operated controls
  + good for users with physical disabilities
  - problem for users who are blind
  - may be difficult for users who cannot stabilize their hands to make fine adjustments (especially sliding)
• Light action
  + low effort, low fatigue
  - can cause multiple activation problems if too close together
• Touch sensitive
  - very difficult for person who are blind to locate without activating.
  - must provide some other (auditory or tactile) feedback for blind users to be able to tell they have activated it.
  - heat or capacitive based touch switches may not react to mouth or headsticks

NOTE: Some diseases such as diabetes and "white finger" can cause loss of sensation in the fingertips. Therefore, controls that are dependent on tactile feedback should not rely on fine tactile sensation.

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D

Figure I-5-a: Individuals with arthritis, artificial hands, hooks, disabilities which restrict wrist rotation, or disabilities which cause weakness, have difficulty with knobs or controls that require twisting. Also difficult for people with loss of upper body strength, range of motion and flexibility as is common with elderly persons. Really should be avoided in bathrooms where soap and water create slippery environment. (Lever handles, now required in many building codes, facilitate access.)

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Figure I-5-b: Concave and non-slip buttons facilitate the use of manipulation devices, artificial hands, hooks and mouthsticks. This is especially true where pressure is required.

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I-6. Maximize the number of people who can ... understand how to operate controls and other input mechanisms.

Problem:

The layout, labeling or method of operating controls and other input mechanisms can be confusing or unclear.

Examples:

• People with reduced or impaired cognitive function:
  • may be confused by complex, cluttered control layouts, with many and/or many types of controls.
  • may have difficulty making selections from large sets.
  • may have trouble remembering sequences (see also M-4).
  • may be confused by dual-purpose controls.
  • may not relate appropriately to controls settings indicated solely by notches/dots or numbers.
• People with reduced or impaired cognitive function, language impairments, illiteracy, or for whom English is a second language:
  • may have difficulty relying solely on textual labels, especially where abbreviations are used, and sometimes have difficulty making associations between label and control.
  • may have trouble with timed responses involving text.

Design Options and Ideas to Consider:

Reducing the number of controls.

• Limiting the number of choices where practical.
• Using layering of controls where only the most frequent or necessary controls or commands are visible unless you open a door or ask for additional levels of commands.(e.g. hiding less frequently used controls, or at least grouping the most frequently used controls together and placing them prominently.)
• Where possible, make products automatic or self adjusting, thus removing need for the controls (e.g., TV fine tuning and horizontal hold).

Simplify the controls.

• Minimizing dual purpose control