The Kōreisha mark (高齢者マーク, elderly car mark) is a statutory sign that is set up in the Road Traffic Law of Japan to indicate "aged person at the wheel". Its official name is "aged driver sign" (高齢運転者標識, kōrei untensha hyōshiki).
The law decrees that when a person who is aged 70 and over drives a car and if his/her old age could affect the driving, he/she should endeavor to display this mark on both the front and rear of the car. Drivers aged 75 and over are obliged to display the mark.
Conversely, the green and yellow shoshinsha mark or wakaba mark denotes new drivers. Both marks are designed to warn other drivers that the marked driver is not very skilled, either due to inexperience or old age.
The system was instituted in 1997; until January 2011, its shape was an orange and yellow teardrop-shaped, and it was accordingly also called "momiji mark" (紅葉マーク, autumn leaf mark). Some people call it "kareha mark" (枯れ葉マーク, dried leaf mark) or "Ochiba mark" (落葉マーク, fallen leaf mark), but this is a more informal title, and considered less polite.
From 1 February 2011, the shape changed to the new, 4-leafed form.
Outside Japan, owners of Japanese classic cars have adopted this symbol, regardless of the driver's age. Japanese car enthusiasts overseas also use the Koreisha mark to indicate that they are an experienced driver as opposed to the Wakaba mark which indicates that they are new or a learner type driver.