Correlation between visibility and traffic safety visual distance in foggy areas during the daytime.

OBJECTIVE: Traffic safety is closely related to the driver's ability to obtain visual information. Low visibility would result in traffic accidents. This study aimed to explore the difference between meteorological visibility and traffic safety visual distance in foggy areas in the daytime, and analyze the difference between dynamic visual ability and static visual ability, so as to calculate the maximum acceptable speed limit that meets the driver's safety visual distance requirement. METHODS: Visual distances under different visibility conditions were collected for 12 passenger car drivers through static and naturalistic driving visual recognition experiments. The power function relation model between driver's static visual distance and meteorological visibility was established, and the attenuation rates of dynamic visual distance at different driving speeds were obtained. RESULTS: Traffic safety visual distance (TSVD) gradually grows with the increase of visibility and finally tends to be stable due to the vision limitation of the human eyes under good weather conditions. The drivers' visual ability decreased while driving dynamically, and dynamic TSVD was shorter than static TSVD. CONCLUSIONS: Traditional meteorological visibility is different from drivers' actual TSVD, but there is a correlation between them. According to the relationship between visibility and dynamic TSVD, the maximum recommended speed limit values under different visibility levels are provided. The calculation of the maximum acceptable speeds under specific visibility conditions can provide a technical basis for road construction and traffic management.