Objects and environments should be designed to be usable, without modification, by as many people as possible
Many people means, people of diverse abilities. It is not just for people who are physically challenged.
Four characteristics of accessible designs:
Perceptibility:
- It is achieved when everyone can perceive the design, regardless of the sensory abilities.
- Present information using redundant coding methods (e.g., textual, iconic, and tactile)
- Provide compatibility with assistive sensory technologies( ALT tags for images on the internet)
- Position controls and information so that seated and standing users can perceive them.
Operability:
- It is achieved when everyone can use the design, regardless of the physical abilities.
- Minimise repetitive actions and the need for the sustained physical effort.
- Facilitate use of controls through good affordances and constraints
- Provide compatibility with assistive sensory technologies( ALT tags for images on the internet)
- Position controls and information so that seated and standing users can perceive them.
Simplicity:
- It is achieved when everyone can easily understand and use the design, regardless of experience, literacy or
concentration level - Remove unnecessary complexity, clearly and consistently code and label controls and modes of operation - Simplification of information, Amplification through simplification
- Use progressive disclosure
- Provide clear prompting and feedback for all actions
- Ensure reading levels accommodate a wide range of literacy.
Forgiveness:
- It is achieved when design minimises the occurrence and consequences of Errors.
- Affordances and Rules and Constraints
- Use confirmations and warnings to reduce the occurrence of errors
- Include reversible actions and safety nets to minimise the consequence of errors(Undo button)
Example:
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An elevator with wide doors permit easy access including for wheelchairs.
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Handrails help people maintain a standing position.
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Two sets of control for seated position and standing position.
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Controls are redundantly code with numbers, icons and braille.
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Feedback is provided aurally and visually.
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Emergency phone system for special assistance.