Textbook of Usability

Universal design is the design of products and environments to be usable by all people, to the greatest extent possible, without the need for adaptation or specialised design. The term was coined by architect Ronald Mace, who established the Center for Universal Design at NC State University.

The seven principles of universal design (Connell et al., 1997):

1. Equitable use — useful and marketable to people with diverse abilities
2. Flexibility in use — accommodates a wide range of preferences
3. Simple and intuitive use — easy to understand regardless of experience
4. Perceptible information — communicates effectively regardless of sensory abilities
5. Tolerance for error — minimises hazards and consequences of accidents
6. Low physical effort — usable efficiently with minimum fatigue
7. Size and space for approach and use — appropriate for any body size or mobility

Universal design is the architectural parallel to digital accessibility, and the principles map cleanly onto software usability:

• "Simple and intuitive use" ↔ Norman's conceptual models
• "Tolerance for error" ↔ error prevention and recovery heuristics
• "Perceptible information" ↔ redundant multimodal encoding

Universal design differs from accessibility in emphasis: accessibility focuses on meeting the needs of people with specific disabilities; universal design aims for solutions that serve everyone without segregating or stigmatising any group. A ramp replacing stairs serves wheelchair users, parents with strollers, delivery workers with carts, and travellers with luggage — one design for many needs.