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Discrete TGSIs are tactile indicators that require a minimum of 45% luminance contrast. These are tactiles that consist of individual units, which are installed onto the pedestrian surface one at a time.
Composite TGSI’s are tactile indicators that require a minimum of 60% luminance contrast which are also discrete tactile indicators, however, they are manufactured using two colours or materials.
Integrated TGSIs require a minimum of 30% luminance contrast. These tactiles are a series of tactile indicators that are incorporated on a backing tile that consists of the same material and colour of the tactiles.
Stair nosing and edging are required to have a contrast strip not less than 50 mm and not more than 75 mm deep across the full width of the path of travel with 30% contrast to the tread background.
Tactile Ground Surface Indicators (TGSI’s) are designed to assist pedestrians with vision impairment to navigate the urban environment safely through visual and sensory stimulus. Generally, people with low vision are able to see colour and differentiate between different colours, however, their ability to discriminate colours may also be impaired. A small percentage of vision impaired persons are completely blind and so, the luminance contrast of walkways and tactile indicators allow for people with low vision to distinguish between surfaces and gather information to detect hazards and safe paths of travel. It is essential that the luminance requirements are met so that the contrast in luminance of tactile indicators relative to that of the surrounding surface are distinguishable to allow for safe navigation.
Below are examples that highlight the importance of luminance contrast between the tactile indicators and substrate. The yellow integrated tactile mats provide a clear distinction between the tactiles and asphalt, allowing people with impaired vision to identify that there is a tactile surface present so that they can determine if a hazard or safe path of travel is present. However, the black integrated tactile mats are very similar in colour to that of the asphalt and provide poor luminance contrast as they both reflect light similarly.
Some other minimum luminance contrast requirements specified in the BCA and Disability (Access to Premises – Buildings) Standards include;
Find out more about luminance contrast requirements for tactiles and stair nosings and how it is calculated.