As a designer or certifier are the “Discrete TGSIS” you are responsible for comply?
What are discrete TGSIs?
Tactile domes that are individually installed.
Discrete TGSIs are not referenced in the deemed-to-satisfy provisions of the BCA. See BCA A0.5(b)
Under BCA Specification A1.3 AS1428, Part 4, 1992, Tactile ground surface indicators for orientation of people with vision impairment, Amdt 1 is referenced. This standard does not reference Discrete TGSIs. Only the unreferenced AS/NZS 1428.4:2002 does.
The key issue with the use of Discrete TGSIs is Luminance contrast, especially with the polished stainless steel type.
Luminance Contrast is the amount of light reflected from one surface or component, compared to the amount of light reflected from the background or base surfaces.
As a reminder the required luminance contrast for TGSIs to the base surface as follows:
Where does this leave us as Designers, Certifies or Access Consultants?
An Alternative Solution for discrete tactiles should be prepared. However to prepare an Alternative Solution testing A certificate must be provided by a NATA laboratory that is “Accredited” to test them that both the required Luminance Contrast and Slip Resistance complies.