A Study on the Visual Behavior Characteristics of Drivers at the Entrance Area of Freeway Tunnels in Foggy Weather

The tunnel entrance area and foggy environments significantly impact drivers' vision, causing changes in drivers' visual behaviors that lead to alterations in driving behaviors, thus affecting traffic safety. To investigate the influence of fog on characteristics of drivers' visual behavior at the tunnel entrance area, a real-vehicle test is conducted in Sanhu Tunnel and Hankou Tunnel in Henan Province, and 24 participants are recruited to analyze the differences in drivers' visual behavior characteristics inside and outside the tunnels under foggy and clear weather, with drivers' fixation and saccade behaviors as the main objects of the study. The results indicate significant differences in drivers' visual behavior characteristics between foggy and clear weather. ①Before entering the tunnel in foggy weather, fixation distribution becomes more concentrated, the percentage of fixation durations exceeding 1 000 ms increases, with foggy conditions at night reaching 29%, average fixation duration increases, the frequency of fixation decreases, the range and efficiency of visual search decrease, and saccades within the range from 0° to 5° accounting for 88.89%, drivers pay less attention to the environments on both sides and try to search for the tunnel portal, demonstrating more cautious driving behavior. ②After entering the tunnel in foggy weather, the range of fixation points expands to varying degrees, average fixation time and average saccade duration increase, the range and efficiency of visual search improve, and drivers pay more attention to the tunnel sidewalls and contour. ③In foggy weather, nighttime has a greater impact on drivers' visual behaviors than daytime, and the level of driving caution increases further. ④During the daytime, fog reduces the visibility of the visual-guiding facilities at the tunnel portal, leading to poor recognition of the tunnel portal, drivers experience a dramatic change in their visual environment, which increases visual load and psychological pressure, significantly increasing driving risk.