Answer:
Step-by-step explanation:
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 stop 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 stop 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 (30", 36" or 48"), according to sign location and traffic speeds.[2][3]
In the United States, stop signs are 30 inches (76 cm) across opposite flats of the red octagon, with a
-inch cm) white border. The white uppercase stop legend is 10 inches (25 cm) tall.[4][5] Larger signs of 35 inches (89 cm) with 12-inch (30 cm) legend and 1-inch (2.5 cm) border are used on multi-lane expressways. Regulatory provisions exist for extra-large 45-inch (110 cm) signs with 16-inch (41 cm) legend and 1+
-inch border for use where sign visibility or reaction distance are limited, and the smallest permissible stop sign size for general usage is 24 inches (61 cm) with an 8-inch (20 cm) legend and
-inch (1.5 cm) border.[6] The metric units specified in the US regulatory manuals are rounded approximations of US customary units, not exact conversions.[5][7] The field, legend, and border are all retroreflective.
Some modern stop signs have flashing LEDs around the perimeter, which has been shown to substantially reduce crashes.[8]