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Tactile Ground Surface Indicators (TGSI’s)

  • August 22, 2018
  • Bruce Bromley

TGSI’s & Luminance Contrast

Tactile Ground Surface Indicator’s (TGSI’s) are designed to assist people with a vision impairment to safely navigate the built environment by the visual and sensory stimulus. It is often mistaken that people who are legally blind are in total darkness. Though it can mean that, it is more likely that legally blind individual can still detect changes and differences in colours. For this very reason, it is essential that TGSI’s meet the minimum allowable luminance contrast ratios.

All TGSI manufacturers should be able to produce official documentation that states their products LRV’s. With these in hand it is possible to calculate luminance contrast ratios and for assistance with this please feel free to use our Contrast Calculators.

As a guide Australian Standard AS1428.4.1 – 2009 has a table in Appendix E that shows the required Y values for lighter and darker surfaces. Please note that the Y value is not the LRV.

Luminance contrast table