Do visual guiding facilities in freeway tunnels affect drivers’ perception of longitudinal safety distance? A simulation experiment

The safety perception of longitudinal distance by drivers in tunnels is critical for road safety. However, existing studies mainly focus on the effects of visual guiding facilities on speed perception and vehicle position, with limited research on their impact on longitudinal distance perception. This study aims to evaluate the effect of different types of visual guiding facilities on drivers’ safety perception of longitudinal distance in freeway tunnels. The experimental design considered the type of facility, including dot-shaped, linear, and ring-shaped visual guiding facilities. The linear visual guiding facilities are further categorized by length. The inter-facility spacing is treated as a variable parameter. Forty participants are involved in simulated experiments, during which subjective perceptions of longitudinal distance and perception reaction time data are collected. The impact of facility variables on safety perception of longitudinal distance is assessed. Dot-shaped visual guiding facilities do not improve drivers’ judgment of longitudinal distance. Ring-shaped visual guiding facilities have the most significant positive impact on drivers’ safety perception of longitudinal distance. The effectiveness of linear visual guiding facilities increases with their length; shorter lengths are less effective. To enhance drivers’ perception of longitudinal distance in tunnel mid-sections, retroreflective rings with a spacing of no more than 200 meters should be installed. Additionally, longer vertical retroreflective stripes can be used to supplement this, with spacing ranging from 50 to 100 meters.