ABSTRACT
In-service safety signs can be damaged beyond the point of usefulness due to natural degradation. This study investigated recognition threshold for discolored safety signs in terms of white pixel concentration and CIELUV color difference. Fifteen safety signs were chosen for study and discoloration was simulated with bandpass filters (Photoshop CS® software). Fifty Hong Kong Chinese familiarized themselves with all the sign referents first, and then the signs were presented in random order with each sign shown progressively from the most deteriorated to the complete version in the recognition task. It was revealed that deteriorated safety signs with white pixel concentration difference and CIELUV color difference higher than the grand mean recognition threshold of 19.34 and 4.30, respectively, might not be accurately recognized and should be restored for use immediately. The lifespan of a safety sign in future could be determined through consideration of the estimated prescribed level of recognition threshold for damaged signs.
