Luminous Performance and Quantity Optimization of Exit Signs in Buildings: Balancing Visibility and Emergency Evacuation Efficiency

Emergency evacuation signage, particularly exit signs installed along building corridors and evacuation routes, is critical for life safety during emergencies. Traditional signage design generally prioritizes maximizing visibility and spatial coverage. However, excessive sign installation may introduce visual clutter and interference among overlapping guidance cues, thereby limiting further improvements in evacuation performance. Therefore, a two-stage method is proposed to explore the optimal balance between luminous performance, installed quantity, and spatial distribution of exit signs for efficient evacuation guidance. First, a controlled experiment involving 30 participants was conducted to establish a U-shaped psychophysical relationship between achromatic contrast and the maximum recognition distance (MRD). The relationship is largely independent of both ambient illumination and observer gender. Second, the MRD data were integrated into Pathfinder to systematically assess how occupant density and sign quantity jointly influence evacuation efficiency. The results demonstrate that the optimal signage configuration shows significant density dependence. In the tested corridor scenario, three signs yield the shortest evacuation time at high occupant density, whereas fewer signs achieve comparable or better evacuation performance at medium and low densities. Moreover, a saturation effect is identified in the benefits of MRD improvement. Once the threshold is exceeded, further increases in MRD yield little or no additional improvement in evacuation efficiency. These findings are discussed in terms of hypothesized interference from overlapping guidance cues and congestion from overlapping signs. The study suggests that future signage design guidelines may benefit from incorporating density responsive and performance-based evaluation. Further experimental and field validations are needed to support broader standardization.