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1991 ADA Standards for Accessible Design

Note: This document, portion of document or referenced document was published prior to the 2010 ADA Standards, and is no longer applicable.

A4.29 Detectable Warnings.

A4.29.2 Detectable Warnings on Walking Surfaces. The material used to provide contrast should contrast by at least 70%. Contrast in percent is determined by:

Contrast = [(B1 - B2)/B1] x 100

where B1 = light reflectance value (LRV) of the lighter area and B2 = light reflectance value (LRV) of the darker area.

Note that in any application both white and black are never absolute; thus, B1 never equals 100 and B2 is always greater than 0.

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