what is the shape of mandatory traffic signs
circular
title: Traffic sign text: international protocols. Such signs were first developed in Europe, and have been adopted by most countries to varying degrees. Various international conventions have helped to achieve a degree of uniformity in Traffic Signing in various countries. Traffic signs can be grouped into several types. For example, Annexe 1 of the Vienna Convention on Road Signs and Signals (1968), which on 30 June 2004 had 52 signatory countries, defines eight categories of signs: In the United States, Canada, Ireland, Australia, and New Zealand signs are categorized as follows: In the United States, the categories, placement, and graphic standards for traffic signs title: Mandatory sign text: can be as little as 30 cm (0.98 ft) in diameter. The mandatory sign group is not used in Australia, Ecuador, or the United States, none of which are signatories to the Vienna Convention. Canada has developed its own style using a green circle, which is not used in any other country. The U.S. and Australia instead uses black arrows and border on taller-than-wide rectangular white signs, often with the word ONLY below the arrow. Below is a chart comparing some of the most common mandatory signs. Mandatory road signs can be used to allocate certain areas to specific vehicles title: Mandatory sign text: Convention on Road Signs and Signals of 1968, and are often seen not just on their own, but used in conjunction with other signs, traffic lights and bollards as a form of visual shorthand within these objects. In Vienna Convention signatories, the mandatory sign is either a light blue circle with a white border (Type A) or a white circle with a red border (Type B). The sign must be at least 60 cm (1.96 ft) across on rural roads, or 40 cm (1.31 ft) in built-up areas, although mandatory signs incorporated in traffic lights, bollards or larger road signs title: Traffic sign text: somewhat more pictorial than their American counterparts. This is also true for Canadian signage. Regulatory signs also follow European practice, with a white circle with a red border indicating prohibitive actions, and a blue circle indicating mandatory actions. White rectangular signs with a red border indicate lane usage directions. Information and direction signs are rectangular, with a green background indicating a state highway, a blue background for all other roads and all services (except in some, where directional signage is white), and a brown background for tourist attractions. Before 1987, most road signs had black backgrounds – diamonds indicated warnings, title: Stop sign text: a black cross. The red octagon with "STOP" in the English language has become the most common version of the stop sign used around the world because STOP is the international standard. However, many countries use different variations. Stop sign A stop sign is a traffic sign to notify drivers that they must come to a complete stop and make sure no other road users are coming before proceeding. 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