Alternative Interfaces for Accessibility


This is a recent article on Jakob Nielsen's web site.



Jakob Nielsen's Alertbox, April 7, 2003:

Alternative Interfaces for Accessibility

Summary:  The key difference between user interfaces for sighted users
and blind users is not that between graphics and text; it's the
difference between 2-D and 1-D. Optimal usability for users with
disabilities requires new approaches and new user interfaces.

The typical advice for making websites accessible is to create a single
design for all users, then ensure that it complies with additional
guidelines for use by people with disabilities. This is also the
approach we take in our own guidelines for accessibility: They aim at
improving usability for users with disabilities by tweaking traditional
websites and intranets to take special needs into account.

The main reason for this single-design-for-multiple-audiences approach
is the assumption that most companies are unable to keep two different
designs up-to-date. Thus, if they optimized a separate design for users
with disabilities, they'd risk it rapidly becoming out of synch with the
"main" website.

For most websites, this assumption is probably true. The average company
allocates very limited resources to serving users with disabilities, so
their best approach is to use these resources to improve the main
design, rather than to design, implement, and maintain a separate site.

However, perfect usability for users with disabilities requires separate
designs optimized for each of the main access modalities. An interface
for blind users, for example, should be designed for auditory
presentation. Such a design is inevitably better than simply reading out
loud something designed for screen-based visual presentation, even if
that presentation is modified to take blind users into account. Of
course, in an ideal world, separate and equally targeted designs would
also be available for low-vision users, users with motor skills
challenges, and so on.

Optimize for Linear Access

The biggest potential gains reside in creating a special design
optimized for auditory presentation. A good 1-D audio design not only
serves blind and low-vision users, but will also help users in cars and
other settings as auditory access to Internet content increases.
There's a fundamental difference between visual and auditory
presentations in terms of dimensionality: screens are 2-D and depend on
layout for presentation, and audio is 1-D and relies on sequence for
presentation. Linearizing a 2-D layout is simply not as usable as having
a good designer create a targeted 1-D layout.

In a 2-D layout, a good graphic designer organizes blocks of information
to provide a visual of the website's structure and to prioritize the
most important tasks by their relative size and 2-D location. For
example, designers typically place the most important Web page elements
in the center of the top screenfull, since that's where sighted users
tend to look first. Although a targeted 1-D audio presentation should
start with the most important information, most audio translations
simply read a 2-D page aloud, starting at the top left, which mainly
contains information that sighted users typically skip. Also, simply
reading aloud eliminates size distinctions, which are key elements in
2-D designs.

The fundamental difference between user interfaces for sighted users and
blind users is thus not the distinction between graphics and text, but
that between 2-D and 1-D. Unfortunately, we don't know much about good
1-D layout for interaction design (we know how to produce good radio
shows, but they are not interactive forms of audio content). However,
it's quite likely that an optimal linearized presentation would make
more use of hypertext than we find in 2-D layouts that benefit from
visual scannability. Thus, a design for auditory use might end up being
more N-dimensional than purely 1-dimensional.

Blind users might also benefit more from a 3-D user interface than
sighted users. I imagine a gestural interface, where users are
surrounded by different types of information located at different spots.
They'd access this information by poking at points in space. Thus,
designers could "park" search results and other key pieces of
information in particular locations, where users could retrieve them
with a gesture. For sighted users, such an interface would be useless:
There would be no words floating in space -- unless they used a clumsy
VR helmet. For blind users, however, gestures and unseen (but easily
remembered) 3-D locations might beat linear read-outs.

Expanded Possibilities

Just as optimal 1-D design benefits sighted users needing hands-free
content access, so, too can designs for users with other disabilities
expand other users' options. Users with low vision, for example, can
only see small amounts of information at any given time. Optimizing the
design to suit their needs also benefits users of mobile devices or
other small-screen devices, who essentially have the same limitations.
Regardless of the targeted user group, all designs must offer the same
functionality and provide access to the same content. A good content
management system will be necessary to ensure that all versions are kept
in synch and no one misses out on updates.

Of course, the approach I advocate here is overly Utopian. I doubt at
present that companies will spend enough money on users with
disabilities to create sufficiently good alternative designs --
especially when such designs will require a completely new set of
usability guidelines. However, the future is more promising: Once
auditory access to Internet content becomes more mainstream, I expect
that resources to create optimal audio designs will be more readily

Accessibility Tutorial

Full-day tutorial on making the web easy to use for people with
disabilities at Lighthouse International in New York City, May 5, 2003.
Based on several usability studies.

Received on Tuesday, 8 April 2003 01:17:57 UTC