Experimental study on human visual response to safety signage under emergency lighting conditions

Reliable recognition of evacuation signage under low-visibility conditions is vital for occupant safety. This study investigates the impact of chroma differences (Δ C *) on visual recognition and introduces a perception-based model tailored for supra-threshold tasks. Through psychophysical testing, recognition performance was quantified using Color Visual Acuity (CVA) across varying brightness, chroma, and hue conditions. Results reveal that CVA decreases with increasing chroma due to perceptual saturation and varies significantly with hue, particularly reduced near yellow (90°) due to S-cone sensitivity limitations. Brightness ( L *) consistently enhances CVA across all conditions. A novel P erceived C olor D ifference (PCD) model was developed, based on spectral radiance differences weighted by human chromatic sensitivity. The model exhibits a robust logarithmic correlation with CVA, outperforming traditional ΔE metrics, which are optimized for near-threshold color discrimination rather than recognition. A dual-threshold criterion, CVA ≥ 4.0 and PCD ≥ 0.0005, is recommended to ensure effective recognition in safety-critical environments. The findings support the design of more effective evacuation signage by linking human visual responses to lighting conditions in low-visibility environments.