Concept
A stop sign is a traffic sign designed to notify drivers that they must come to a complete stop and make sure the intersection is safely clear of vehicles and pedestrians before continuing past the sign. In many countries, the sign is a red octagon with the word STOP, in either English or the national language of that particular country, displayed in white or yellow. The Vienna Convention on Road Signs and Signals also allows an alternative version: a red circle with a red inverted triangle with either a white or yellow background, and a black or dark blue STOP. Some countries may also use other types, such as Japan's inverted red triangle stop sign. Particular regulations regarding appearance, installation, and compliance with the signs vary by some jurisdiction. The 1968 Vienna Convention on Road Signs and Signals allows for two types of stop sign as well as several acceptable variants. Sign B2a is a red octagon with a white legend. The European Annex to the convention also allows the background to be "light yellow". Sign B2b is a red circle with a red inverted triangle with either a white or yellow background, and a black or dark blue legend. The Convention allows for the word "STOP" to be in either English or the national language of the particular country. The finalized version by the United Nations Economic and Social Council's Conference on Road Traffic in 1968 (and in force in 1978) proposed standard stop sign diameters of 600, 900 or 1200 mm (24", 36" or 48"). The United Kingdom and New Zealand stop signs are 750, 900 or 1200 mm (about 30, 36 or 48 inches), according to sign location and traffic speeds. In the United States, stop signs are across opposite flats of the red octagon, with a 3/4-inch (2 cm) white border. The white uppercase legend is tall. Larger signs of with legend and border are used on multi-lane expressways. Regulatory provisions exist for extra-large signs with legend and 1 3/4-inch border for use where sign visibility or reaction distance are limited, and the smallest permissible stop sign size for general usage is with an legend and 5/8-inch (1.
