<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (April 2016) (Learn how and when to remove this template message) </Td> </Tr> <P> A stop sign is a traffic sign to notify drivers that they must make sure no cars are coming and stop before proceeding . </P> <P> The 1968 Vienna Convention on Road Signs and Signals allows for two types of stop sign, as well as three acceptable variants . Sign B2a is a red octagon with the inscription "STOP" in white . Sign B2b is a red circle with a red inverted triangle with either a white or yellow background, and the inscription "STOP" in either black or dark blue . 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 the standard stop sign diameters of 600, 900 or 1200 mm . </P>

What kind of sign is a stop sign
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