A mudflap is used in combination with the vehicle fender to protect the vehicle, passengers, other vehicles, and pedestrians from mud and other flying debris thrown into the air by the rotating tire. A mudflap is typically made from a flexible material such as rubber that is not easily damaged by contact with flying debris, the tire, or the road surface.
Mudflaps can be large rectangular sheets suspended behind the tires, or may be small molded lips below the rear of the vehicle's wheel wells. Mudflaps can be aerodynamically engineered, utilizing shaping, louvers or vents to improve airflow and lower drag.
While some flaps are the plain colour of rubber, many contain company logos or other art, or sometimes advertisements. One popular image is cartoon character Yosemite Sam with the words "Back Off!". Another is the mudflap girl, an attractive woman's silhouette, sitting with her hair being blown back in the wind.
In the United States, there are mudflap regulations that vary from state to state.