A stop sign is a traffic sign that tells the driver to make sure no cars come in and slow down before moving on.

Parking signs originated in 1915, Michigan. The first stop sign, with black letters on a white background, is 24 x 24 inches (61 cm x 61 cm) long and smaller than the current stop sign. With the popularity of parking signs, a committee supported by the National Association of Highway Officials (AASHO) met in 1922 to standardize them and chose the octagonal shape that has been used in the United States since. The unique octagon shape of the sign allows the driver to face the back of the sign to identify the approaching driver with a stop sign and prevent confusion with other traffic signs. It was also chosen so that it can be easily identified at night because the original logo is not reflective. The National Conference on street and road safety (ncshs), which competes with AASHTO, promotes the use of smaller pink yellow parking signs.