Tyrer Accessibility Scale

The Tyrer Accessibility Scale classifies civilisations by the proportion of environmental information accessible to every perceiving being, regardless of sensory modality. It is the map of the Tyrer Framework: if Tyrer's Law explains why inaccessibility grows, the scale shows where a civilisation stands and where it could stand.

It is modelled on the Kardashev Scale, which ranks civilisations by the energy they harness, and it is independent of it. "A society that can harness the energy output of its star but cannot ensure that a blind citizen can safely cross a street has mastered one dimension and failed at the other."

Terms

• Environmental information: all the state describing the geometry, dynamics and meaning of a physical or social environment.
• Perceptual channel: any biological or technological route by which that information reaches a conscious observer.
• Information casualty: information failing to arrive in time.

Type 0: Visual Dominance Civilisation

Information is encoded visually first, and accessibility is retrofitted translation, losing something at every step. Screen readers interpret layouts never designed to be read in sequence; alt text describes images never designed to carry meaning in words. Full WCAG compliance is the best this paradigm offers: "The floor holds, but the ceiling is fixed." Human civilisation in the early twenty-first century is Type 0.

Type I: Structured Information Civilisation

Systems carry explicit semantic structure, and every interface, visual, spoken or for an agent, is generated from the same data as an equal, native expression. Accessibility becomes an engineering requirement rather than an accommodation. The line is crossed "when the accessible interface stops being a retrofit and starts being a native sibling generated from shared source data". See generative accessibility.

Type II: Environmental Metadata Civilisation

The physical world becomes an information network: objects, buildings and streets broadcast machine-readable descriptions of their geometry, state and purpose. A door announces itself; a shop declares its contents. "Mute objects cease to exist." Casualties become infrastructure failures, not personal misfortunes.

Type III: Perceptual Sovereignty Civilisation

No observer's access to reality depends on which senses they happen to have. Description and direct perception merge, and "the concept of a sensory disability, in its current meaning, has no referent". The probability of a casualty approaches zero: the Zero Information Casualty condition.

A note on register

Types 0 and I are engineering claims that can be tested now; Types II and III are the philosophical extension. "The near end is a measurement; the far end is a direction." Moving from Type 0 to Type I needs no exotic technology, only discipline, information architecture and the political will to treat perceptual access as infrastructure. "The question is not capability but priority."

Behind the scenes

A real idea, from The Tyrer Framework, by Charli-Jo Tyrer (Carrados, 2026), Part Two, which includes a diagram of the scale. This entry summarises it; the paper is the authority.