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Resources on Accessible/Universal Design Principles and Performance Measures
Accessibility addresses access to effective use of a product by all people, including persons with disabilities. Most products have a degree of accessibility, in that they cannot be used successfully and completely by all persons; our R3 (Accessibility Metrics) project is developing measurement tools to determine degrees of accessibility for categories of medical instrumentation. While there is often synergy with usability (extent to which a product can be used by specified users to achieve specified goals in an effective and efficient manner, to the satisfaction of these users; e.g., "ease of use" is desirable), and accessibility is sometimes considered a category of usability, at times making an interface more fully accessible may lower the degree of usability for some people. For instance, an interface may appear more complex when multimodal options are added that make it accessible to more people. Multimodality refers to support for transformations to alternative sensory interface modes for a channel (e.g., between text and speech), such that more than one modality is available to access content.
Accessible design targets removing barriers that prevent individuals from participating in the use of a product, i.e. extending a design to maximize the number of potential customers who can readily use the device or service. There are two basic strategies for enhancing access through design: direct access (direct adaptations to product designs that significantly improve their accessibility) and assistive access (product interfaces that enable an add-on assistive technology to provide the user with full access). Legislation such as Section 508 of the Rehab Act allows either strategy.
There are many resources that address accessible design, including a number on the Web:
U.S. Access Board site and U.S. government's usability.gov site, including research-based usability guidelines
Trace Center site (includes information for accessible
web sites and Section 508 guides)
Resource Guide for Accessible Design of Consumer Electronics (1996), available through TIAaccess site maintained by Electronic Industries Alliance/Electronic Industries Foundation
W3C Web Accessibility Initiative site (W3C is the World Wide Web Consortium; see especially Quick Tips, and Web Content Accessibility Guidelines for HTML and XML)
Enabling Technologies Laboratory (ETL) site
Company sites addressing accessibility
(e.g., Microsoft site , IBM site, SUN site)
See also the RERC-AMI's pages on Usability Analysis Tools for Medical Devices (part of Project R2) and on Multimodal Interfaces (part of Project D3.2)
A good reference from the engineering academic community is Erlandson RF and Babbitt BC (2001), "The Movement of Accessible Design Principles into Mainstream Engineering: Now and Then," in Emerging & Accessible Telecommunications, Information & Healthcare Technologies, Winters JM, Robinson C, Simpson R & Vanderheiden G., eds, pp. 2-18, RESNA Press, Arlington. (Note: if a project design supervisor would like a free copy of this book, which includes many other chapters related to accessibility and design, send an email with mailing address to jack.winters@mu.edu.)
Universal Design is the design of products and environments to be effectively and efficiently usable by people with a wide range of abilities, to the greatest extend possible, without the need for adaptation or specialized design. It clearly relates to usability and accessibility, and converges with the concepts of Universal Usability (usable by all) and Universal Accessibility (accessible by all). Designers should be especially cognizant of the Principles
of Universal Design (available as pdf), as developed
through the Center for Universal Design by a working
group in 1997 (Story, 1998;
Story and
Mueller,
2002):
1. Equitable Use
2. Flexibility in Use
3. Simple and Intuitive Use
4. Perceptible Information
5. Tolerance for Error
6. Low Physical Effort
7. Size and Space for Approach and Use
These principles were developed for both the built environment and product
design. Since our focus is on product design, it is instructive to consider, next
to each principle, more pragmatic performance measures. The
following
table includes both the original consensus
guidelines
from
the working
group (left column)
and
field-tested
usable product
design
concepts, for your consideration. Of note is that many of these cannot always
be fully achieved, and the considerations within the table below often can't be answered with a "yes" or "no" but have a degree of truth on a continuum. But they are worth striving
for.
Universal Design: Principles
& Performance Measures
[adapted from Story and Mueller (2002)] |
|
Performance Measures for Products
|
| Principle One - Equitable Use: The design is
useful and marketable to people with diverse abilities |
| Provide the same means of use for all users; identical whenever
possible; equivalent when not. |
All potential users could use this product in essentially
the same way, regardless of differences in personal capabilities. |
| Avoid segregating or stigmatizing any users. |
Potential uses could use this product without feeling segregated or stigmatized
because of differences in personal capabilities. |
| Make provisions for privacy, security, and safety equally available
to all users. |
Potential users of this product have access to all features of privacy,
security, and safety, regardless of personal capabilities. |
| Make the design appealing to all users. |
This product appeals to all potential users. |
| Principle Two - Flexibility in Use: The design accommodates a wide range
of individual preferences and abilities |
| Provide choice in methods of use. |
Every potential user can find at least one way to use this product effectively. |
| Accommodate right- or left-handed access and use. |
This product can be used with either the right or left had alone. |
| Facilitate the user's accuracy and precision. |
This product facilitates (or does not require) user accuracy and precision. |
| Provide adaptability to the user's pace. |
This product can be used at whatever pace (quickly or slowly) the user
prefers. |
| Principle Three - Simple and Intuitive Use: The design is easy to understand,
regardless of the user's experience, knowledge, language skills, or current
concentration level |
| Eliminate unnecessary complexity. |
This product is as simple and straightforward as it can be. |
| Be consistent with user expectations and intuition. |
An untrained person could use this product without instructions. |
| Accommodate a wide range of literacy and language skills. |
Any potential user can understand the language used in this product. |
| Arrange information consistent with its importance. |
The most important features of this product are the most obvious. |
| Provide effective prompting and feedback during and after task completion. |
This product provides feedback to the user. |
| Principle Four - Perceptible Information: The
design communicates necessary information effectively to the user, regardless
of ambient conditions or
the user's sensory abilities. |
| Use different modes (pictorial, verbal, tactile) for redundant presentation
of essential information. |
This product can be used without hearing. |
| Maximize "legibility" of essential information. |
This product can be used without sight. |
| Differentiate elements in ways that can be described (i.e., make it easy
to give instructions or directions). |
The features of this product can be clearly described in words (e.g.,
in instruction manuals or on telephone help lines). |
| Provide compatibility with a variety of tech niques or devices used by
people with sensory limitations. |
This product can be used by persons who use assistive devices (e.g.,
eyeglasses, hearing aids, sign language, or service animals). |
| Principle Five - Tolerance for Error: The design minimizes hazards and
the adverse consequences of accidental or unintended actions. |
| Arrange elements to minimize hazards and errors: most used elements,
most accessible; hazardous elements eliminated, isolated, or shielded. |
Product features are arranged according to their importance. |
| Provide warnings of hazards and errors. |
This product draws the user's attention to errors or hazards. |
| Provide fail safe features. |
If the use makes a mistake with this product, it won't cause damage or
injure the user. |
| Discourage unconscious action in tasks that require vigilance. |
This product prompts the user to pay attention during critical tasks. |
| Principle Six - Low Physical Effort: The design can be used efficiently
and comfortably and with a minimum of fatigue. |
| Allow user to maintain a neutral body position. |
This product can be used comfortably (e.g., without awkward movements
or postures). |
| Use reasonable operating forces. |
This product can be used by someone who is weak or tired. |
| Minimize repetitive actions. |
This product can be used without repeating any motion enough to cause
fatigue or pain. |
| Minimize sustained physical effort. |
This product can be used without having to rest afterward. |
| Principle Seven - Size and Space for Approach & Use: Appropriate size
and space is provided for approach, reach, manipulation, and use regardless
of user's body size, posture, or mobility. |
| Provide a clear line of sight to important elements for any seated or
standing user. |
It is easy for a person of any size to see all the important elements
of this product from any position (e.g., standing or seated). |
| Make reach to all components comfortable for any seated or standing user. |
It is easy for a person of any size to reach all the important elements
of this product from any position (e.g., standing or seated). |
| Accommodate variations in hand and grip size. |
This product can be used by a person with hands of any size. |
| Provide adequate space for the use of assistive devices or personal assistance. |
There is enough space to use this product with devices or assistance
(e.g., wheelchair, oxygen tank, or service animal). |
| |
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Story, M.F. (1998) Assessing usability: The principles of universal design. Assistive Technology, 10:4-12.
Story, M.F. and Mueller, J., (2002) Universal Design Performance Measures for Products: A Tool for Assessing Universal Usability, in Emerging and Accessible Telecommunications, Information and Healthcare Technologies (Winters, J.M., Robinson, C.J., Simpson, R.C. and Vanderheiden, G.C., eds.), pp. 19-28, RESNA Press, Arlington.
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