Overview
ISO 11428:1996 - "Ergonomics - Visual danger signals - General requirements, design and testing" specifies safety and ergonomic criteria for visual danger signals so they can be perceived, discriminated and acted on within a defined signal reception area. The standard covers design intent, required physical measurements (luminance/illuminance/contrast), subjective visual checks and recommendations for signal behaviour (colour, temporal pattern, location and duration). It excludes written/pictorial indicators, data display units and special public-transport/public-disaster regulations.
Key topics and requirements
- Detectability
- Distinguishes luminous area vs point sources (visual angle criteria given).
- For area sources, required luminance ratio (contrast): visual warning ≥ 5× background; visual emergency ≥ 10× background (i.e., emergency ≥2× warning).
- For point sources, detectability is based on pupillary illuminance relative to background luminance (measurement guidance provided).
- Flashing is required for emergency signals; recommended flash frequency ~2–3 Hz.
- Discriminability
- Use at least two distinguishing characteristics (colour, location, temporal pattern, shape).
- Colour assignment: warning = yellow/yellow‑orange, emergency = red. If colours alone are insufficient, emergency intensity must be ≥2× warning.
- Relative position: red above yellow when vertically stacked; two red lights horizontally aligned.
- Location & field of vision
- Signals should be placed within the field of vision of people in the signal reception area; multiple signals may be required so at least one is visible from any point.
- Glare, distance & duration
- Avoid impairment by glare and limit signal self‑glare.
- Keep observer distance as short as practicable (illuminance falls with distance squared); consider transmissivity reductions (fog, smoke).
- After action, downgrade or switch off signals; use an ALL CLEAR signal per ISO 11429.
- Verification
- Physical measurements (luminance/illuminance/contrast) recommended.
- Subjective visual check with representative users (include persons >45 years, acuity
