Tactile Ground Surface Indicators
Tactile Ground Surface Indicators (TGSIs) warn people who are blind or vision impaired that they're approaching a hazard: a set of stairs, a ramp, or an overhead obstruction under 2 metres.
The BCA references TGSIs at D3.8, calling up AS 1428.4 for stairs, escalators, travelators, ramps and overhead hazards.
Getting it right
TGSIs need to be set back 300mm (±10mm) from the hazard, run the full width of the approach, sit at the specified depth, and carry sufficient luminance contrast against the surrounding surface. The two failures we see most often on site: not enough luminance contrast, and indicators placed incorrectly on landings rather than at the top and bottom of the actual hazard.