Unraveling the impact of fog on driver behavior in highway tunnel entrances: A field experiment.

Objectives: This research aims to (1) study the visual and psychological characteristics of drivers in foggy tunnel entrances, (2) compare driver behavior inside and outside foggy tunnels, and (3) propose improvement ideas based on the study results.

Methods: A realistic vehicle trial was conducted. Eight participants completed trials in both foggy and clear zones on the same roadway. Drivers' physiological and psychological properties were analyzed using gaze, saccade, pupil, and heart rate as primary indicators. Pupil area change rate and heart rate variability (HRV) were used as secondary indicators.

Results: Visibility and tunnel area had a significant impact on drivers' visual and psychological traits. For instance, drivers in the foggy zone exhibited longer fixation duration, larger pupil area, faster heart rate, and greater HRV. Moreover, the foggy zone inside the tunnel heightened drivers' visual discomfort and psychological tension.

Conclusion: The study suggests a high risk associated with driving in the entrance area of highway tunnels during foggy conditions, particularly after entering the tunnel. This situation significantly increases drivers' visual and psychological load. Furthermore, the effectiveness of retro-reflective facilities diminishes. Therefore, employing more self-illuminated or actively illuminated visual guiding facilities is recommended to aid drivers in acquiring traffic information.