The vehicle side structure includes a fender having an outer opening at an upper portion thereof, a fender liner disposed inside the fender and covering an upper portion of the front wheel and having a liner opening at an upper portion thereof, and a duct connecting the liner opening and the outer opening and guiding air from the liner opening to the outer opening. The outer opening has first to fifth fender vanes and the duct has first to fifth duct vanes. The surfaces of the first to fifth fender vanes and the surfaces of the first to fifth duct vanes are disposed so as to be continuous in the flow direction.

Mud flaps having one or more decorative and functional accessories attached to the mud flaps, mud flap kits for forming decorative and functional mud flaps, and mud flap accessories suitable for use with and attachment to mud flaps are provided. Methods of making decorative and functional mud flaps, mud flap kits for forming decorative and functional mud flaps, and mud flap accessories are also provided. Methods of using decorative and functional mud flaps, mud flap kits for forming decorative and functional mud flaps, and mud flap accessories on mud flaps, for example, on a truck having 18 wheels, are also provided.