Driving safety of low-position lighting in highway tunnels based on visual performance

To evaluate the lighting environment quality and driving safety of low-position lighting in highway tunnels, this study simulated three lighting schemes (high-position, low-position, and low-position with auxiliary LED strips on maintaining road) using DIALux software for a two-lane unidirectional tunnel. Key parameters for low-position luminaires were optimized, and drivers' obstacle recognition reaction times, gaze distribution patterns and pupil diameter dynamics were tested by visual performance experiments. The results indicate that the optimal parameters for low-position lighting, when using flat light technology luminaires better adapted to low-position lighting, are as follows: lamp spacing of 6–7 m, mounting height of 1.1–1.3 m, staggered arrangement, and auxiliary lighting power of 1 W/m. Compared to high-position lighting, low-position lighting reduced the threshold increment by 47.1%, increased small target visibility by 569%, and shortened drivers’ reaction times for near-roadway obstacles by 25%, significantly enhancing obstacle recognition. The pupil diameter variation rates across different lighting configurations all below 10% indicate that low-position lighting did not induce psychological states of tension or discomfort during driving. Although low-position lighting exhibited slightly lower longitudinal uniformity and longer reaction times for elevated targets, these limitations were effectively resolved by auxiliary LED strips. Overall, low-position lighting substantially improves driving safety and comfort in highway tunnels.