Usability and Accessibility: Interplay

Usability

As a simple definition, "usability" measures how well people can understand and successfully use a product, service, or website. Usability issues typically boil down to efficiency, accuracy, and user satisfaction.

Accessibility

"Accessibility" measures how well people with disabilities can use a product, service, or website. The disabilities may be permanent, e.g., blindness, or temporary, e.g., trying to listen to news on a TV in a noisy sports bar.

Interplay between usability and accessibility

An unusable accessible product?

It stands to reason that if a product, service, or website has serious usability problems, making it accessible does not provide much benefit. People with disabilities will find it difficult to use, and they may be reluctant to use it no matter how "accessible" it is.

If the techniques for improving accessibility are poorly chosen, then a previously usable product may be rendered unusable (or less usable). For example, users who are blind may need a device that talks to them, but those who are not blind may become quickly frustrated with the device as it chatters away, because they have no need for the speech output (which becomes noise to them).

Adding accessibility to the detriment of general use is not good business. It may win a contract initially, based on accessibility, but in the long run ease-of-use may be the more important factor for the continued success of the product.

A product with hard-to-use accessibility features?

Accessibility is about more than conformance with technical regulations. A designer might follow all of the accessibility regulations, but still create a solution that the majority of people with disabilities cannot use. For example, in the days before Flash accessibility, many people developed "accessible" web pages but had a Flash intro to their website, which was inaccessible to users who were blind and using screen readers. It would be like having a building with wheelchair-accessible bathrooms but no wheelchair ramps into the building.

Just like any other product feature, an accessibility feature should be tested by users, (i.e., people who have disabilities) or by using a simulation of disabilities.

Benefits of measuring usability and accessibility together

Usability and accessibility are most appropriately measured through user testing, and sometimes in design, accessibility and usability issues must be addressed simultaneously.

It is common for accessibility evaluations to turn up a good number of usability issues in addition to the identification of accessibility issues.

In addition, increasing accessibility for people with disabilities may also help users who do not regard themselves as having disabilities but who have some form of situational limitation. For example, making a cellular phone accessible to people who are blind might increase the usability of the device for users whose visual attention is directed elsewhere (e.g., using a "talking" phone while driving a car).

Summary

Accessibility and usability are intertwined. Your design team, and any accessibility consultants that you hire, should be aware of this interplay. Understanding and solving usability problems may be a prerequisite before attempting to solve accessibility problems.

Learning More

If you want to learn more about usability and accessibility, check out these resources:

• Accessibility and the User-Centered Design Process, from ITTATC, which defines accessibility and usability and explains how accessibility can be incorporated into the user-centered design process.
• The Usability Professionals Association, which supports usability specialists, people from all aspects of human-centered design, and the broad family of disciplines that create the user experience in promoting the design and development of usable products.
• The Human Factors and Ergonomics Society, which promotes the discovery and exchange of knowledge concerning the characteristics of human beings that are applicable to the design of systems and devices of all kinds.
• Special Interest Group on Computer-Human Interaction (SIGCHI), which brings together people working on the design, evaluation, implementation, and study of interactive computing systems for human use.