How are road traffic signs classified?

　　Road traffic signs are divided into two major categories: main signs and auxiliary signs.

　　The main logo is further divided into:

　　Warning signs, prohibition signs, directional signs, tourist area signs, and road construction safety signs.

　　Warning sign: A sign that alerts vehicles and pedestrians to dangerous locations. It is shaped like an equilateral triangle, with a yellow background, black border, and black graphic design.

　　Prohibition signs are used to indicate that certain vehicle or pedestrian traffic activities are prohibited or restricted. These signs are typically circular in shape, though some may be octagonal or equilateral triangles with their apex pointing downward. The standard color scheme for these signs is white background with a red circle, a red diagonal bar, and black symbols. The "No Parking" sign, however, features a blue background, a red circle, and a red diagonal bar.

　　Directional signs are signs that provide information about road directions, locations, and distances. With the exception of location identification signs, milestone signs, and merge/diverge signs, these signs typically have a rectangular or square shape. As for their colors, signs on ordinary roads feature a blue background with white markings, while signs on expressways have a green background with white markings.

　　Auxiliary signs are signs positioned immediately below the main sign, serving to provide supplementary information. They are rectangular in shape, with a white background, black text, and a black border. These signs are used to convey information that cannot be fully expressed by the main sign itself—such as time periods, vehicle types, reasons for warnings and prohibitions, areas, or distances.