INFO1111 Chap.11 Accessibility and Human-Centred Design
Accessibility and Human-Centred Design
This chapter draws on the guest lecture about working with people with different abilities, which links communication, collaboration and ethics.
It opens with interfaces that misled capable users: a transport-card top-up machine whose last step is easy to miss, the Three Mile Island control panel whose light showed an electrical signal rather than the state of a valve, and Air Inter Flight 148, where a descent angle was taken as a descent rate in a different mode.
It defines human-computer interaction, traces how the field widened as computers moved from technical specialists to everyone, and separates user experience, accessibility and universal design. It lists the lecture's accessibility examples, from captions to simple language, and shows how a single fix often helps several groups.
It ends with the ethics of research and design with people with disabilities: informed consent, privacy, secure data, consultation with families and ethical clearance.
What this chapter covers
- 01
Interfaces that mislead capable users
- 02
Signal versus state in safety-critical displays
- 03
Mode confusion and the Flight 148 redesign
- 04
Human-computer interaction and its widening scope
- 05
User experience, accessibility and universal design
- 06
Accessibility examples that help several groups
- 07
Ethics of designing and researching with people with disabilities
Worked example · free
An accessibility check for a lecture-recording player
- +1No captions: excludes students with hearing difficulties and anyone watching in a noisy place; add captions to every recording.
- +1Small, low-contrast controls: hard for students with low vision and for anyone skimming quickly; enlarge them and raise contrast.
- +1Hidden shortcuts: students who cannot use a mouse depend on the keyboard; document the shortcuts and make every control reachable by keyboard.
Key terms
- Human-Computer Interaction
- The discipline concerned with designing, evaluating and implementing interactive computing systems for human use.
- User Experience
- All aspects of an end user's interaction with a company, its services and its products.
- Accessibility
- Designing so that people with different abilities can use a product, service or space by removing barriers.
- Universal Design
- Designing for the widest range of people from the start instead of adding special fixes later.
- Mode Confusion
- An error in which a user believes a system is in one mode while it is in another, as on Flight 148.
- Informed Consent
- A participant's agreement to take part in research after understanding what it involves.
Accessibility and Human-Centred Design FAQ
What is the difference between accessibility and universal design?
Accessibility removes barriers so people with different abilities can use something. Universal design aims, from the start, for something usable by as many people as possible, avoiding special fixes added later.
What went wrong at Three Mile Island from an interface point of view?
A control-panel light showed that power to a valve's solenoid had been cut, which operators read as the valve being closed. The valve was stuck open, so the problem was diagnosed hours late.
What is mode confusion?
Believing a system is in one mode when it is in another. On Air Inter Flight 148 a 3.3 degree descent angle was taken as 3,300 feet per minute, and the aircraft struck a mountain.
How does accessible design help people without disabilities?
Captions also help people in noisy places, ramps help parents with prams and travellers with luggage, and large high-contrast text helps people reading quickly. That second group is the core of the universal-design case.
What ethical issues arise when designing with people with disabilities?
The lecture lists a sensitive area needing a careful approach, informed consent, consultation with family members, participant privacy, securely stored data and ethical clearance. Its findings add respect for empathy, dignity and privacy.
Exam move
Learn the three opening cases as one-line lessons: the forgotten final step, signal versus state, and mode confusion. Then test any interface you use this week against them: does it show the real state, make modes distinct and confirm the last step? Learn the definitions of HCI, user experience, accessibility and universal design as a set, since a question may ask you to separate two of them.
For the accessibility examples, memorise each with both groups it helps. Link the chapter to the ACS Code: Respect for Others asks for fairness and inclusivity in system design, and Trustworthiness asks for user-friendly systems, so an accessibility failure is an ethics question as well as a usability one. If your Skills assignment aspect is usability, use these checks to write requirements a tester could verify.
Try one assistive feature on your own phone or laptop for ten minutes, such as a screen reader, captions or high-contrast mode, and note what a familiar app gets right or wrong. Concrete observations of that kind make an exam answer about accessibility far more convincing than a list of principles.
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