Failure Mode

In accessibility evaluation, any hindrance caused by a product or web site that prevents a user with a disability from achieving a goal with the same effectiveness, efficiency or safety as a non-disabled user. The term is borrowed from reliability engineering and is used to distinguish accessibility problems (which affect real users in real contexts) from mere guideline non-conformances, which may or may not cause an actual user-facing problem. Identifying failure modes typically requires scenario-based analysis such as a Barrier Walkthrough or user testing with assistive technology.