Understanding accessibility challenges – PB Docs 2017

When designing and developing software applications and Web pages
that you want to make accessible to people with disabilities, there are
four general types of impairments you need to consider:

Visual impairments

Application users who are blind require text equivalents for all
graphic images and videos available to the sighted user. The text needs to
convey content that is conceptually equivalent to the information provided
in graphical form, so that assistive technologies such as screen and
braille readers can make the information fully accessible. All user
interface (UI) elements must have text or menu equivalents, and blind
users need keyboard equivalents for entering input that a sighted user
would enter with a mouse.

To accommodate users who are color blind, you should avoid using
color as the sole means of conveying information. Using fill patterns in
addition to colors in graphs and other images is one strategy for
supplementing information conveyed by color. Auditory cues can serve as an
alternative way of presenting warnings or other content signaled by color
only.

By enabling high contrast support, you can allow color-blind users
and users with low vision to adjust default system colors and fonts to
make areas of a window or Web page easier to distinguish. Users with low
vision also use hardware or software magnifiers to enlarge the pixels on a
display, and they depend on alternate text to get some of the information
presented in images.

Hearing impairments

Users who are deaf or hard of hearing require visual representations
of auditory information. You might need to provide alternate visual cues
in your application for audible warnings, for example. Blinking text is
one alternative, though the blink rate must be within a certain range to
avoid causing problems for users with seizure disorders. Audio tracks
require transcripts, and videos might require closed captioning.

Technology to assist with hearing impairments includes voice
recognition products that can convert auditory information to text or sign
language. Important also are TTY/TDD modems that connect computers with
telephones and convert typed ASCII text output to Baudot code, which is
what deaf individuals commonly use to communicate over the
telephone.

Limited mobility

Users with limited mobility often have difficulty handling hardware
and media, but input is typically their biggest challenge. Depending on
the disability, mobility-impaired users might need to use voice
recognition or an on-screen keyboard with an electronic switch, tracking
ball, or joy stick. They might enter input at a slower pace, which means
that timers and response times should be adjustable. Systems with built-in
intelligence can provide cues to cut down the amount of input required.
For Windows applications, the FilterKeys feature is available to slow the
keyboard repeat rate, and the Windows StickyKeys feature allows users to
enter multiple keystrokes such as Ctrl/Alt/Delete as key sequences.

Cognitive impairments

Reading difficulties, an inability to process visual or auditory
information, problems with text input, and short-term memory problems can
all affect a user’s access to the content of software and Web
applications. Use of clear, simple language, enforcement of consistent
design, and presentation of the same information in redundant format, such
as both audio and video, can all help users with cognitive impairments to
access information. Providing adjustable response times is important to
those whose comprehension is slower than normal. Making content available
to screen readers to reinforce visual representation is another strategy
for aiding comprehension of people with cognitive impairments.

General suggestions

For Web display, it is important to use elements for all markup
instead of manipulating text features such as font size directly. Visual
appearance should not be the only indicator of function for text elements.
Element markup allows assistive technologies such as screen readers to
announce text elements such as headings by their function.

Good design for accessibility benefits not only those with
disabilities, but users in general. By enforcing a consistent interface
design, using simple language, ensuring ease of navigation, and providing
the same information in a variety of ways, you can make your applications
more usable for everyone.

For more information

For general information about making Web sites accessible, see the
World Wide Web Consortium Web site at http://www.w3.org/ and the Utah
State University WebAim Web site at http://www.webaim.org.

For information on how your users can adjust various browsers for
better legibility, and for ways to accommodate vision impairments in
general, see the Lighthouse International Web site at
http://www.lighthouse.org/.