Tactile Ground Surface Indicators (TGSIs) require a luminance contrast against their ground background surface to help people visually identify the TGSIs and be warned that they are approaching a potential hazard (i.e. a roadway, step, overhead obstacle) or the commencement of a ramped accessway. This document explains each type of TGSI and the minimum luminance contrast requirements from AS/NZS 1428.4.1.