Evaluating the Degree of Visibility Deterioration Perceived by Drivers during Snowstorms

Road closures and multi-vehicle collisions often result from poor visibility caused by snowstorms in cold snowy regions. It is therefore important to grasp visibility conditions in snowstorms. Currently, visibility meters are used to determine visibility based on the MOR (meteorological optical range) value calculated from atmospheric extinction coefficients or scatter coefficient measurements. However, in road traffic environments, delineators and various other visual guides are installed along routes, and the visibility perceived by drivers in snowstorms may vary even for the same MOR value. Despite this, no parameter has yet been devised to support comprehensive evaluation of visibility deterioration. Accordingly, this study investigated the relationship between MOR values measured using a visibility meter and visibility/driving difficulty as perceived by drivers, and also examined a method for the rating index of visibility deterioration.