Optimization of tunnel entrance lighting under dynamic visual conditions based on perceived contrast threshold and recognition time analysis

Accurate determination of perceived contrast threshold C min is essential for optimizing the design and evaluation of tunnel entrance lighting. However, conventional methods often fail to adequately capture the C min requirements under dynamic driving conditions. This study analyses the interactive effects of tunnel external luminance ( L e ) and tunnel entrance road surface luminance ( L b ) on drivers’ obstacle recognition ability. Under both positive and negative luminance contrast conditions, the C min required to achieve reliable recognition (80% perception probability) and the associated recognition time ( T r ) were determined across various luminance combinations. The results indicate that compared to the result from the fixed value stimulation involving static visual targets, the C min required for drivers to reliably recognize a fixed obstacle under simulated dynamic driving conditions increased by up to 35% ( L e = 4000 cd m −2 , L b = 75.8 cd m −2 ). The required L b rises in a nonlinear and accelerated manner as L e increases, to maintain the same visual recognition efficacy. Visual recognition performance under negative luminance contrast conditions is significantly better than under positive contrast, which is characterized by smaller C min and shorter T r . Luminance combination models for general safety and high safety recognition time are established. A comparison with existing standards revealed the limitations of current specifications for tunnel entrance luminance design.