The standardisation of road signs, signals and markings is a matter that has received a great deal of attention over the years. For instance, in the 2005–6 session of the United Nations, Resolution A/RES/60/5 implored nations to adhere to the UN Convention on Road Signs and Signals. The most significant progress towards this end has come in the shape of the Vienna Convention on Road Signs and Signals. The convention was signed in over 70 countries, mostly in Europe but also in Asia and Africa, and ratified in over 65 countries, including Albania, Bahrain, Belarus, Belgium, Bosnia and Herzegovina, the Central African Republic, Chile, Côte d’Ivoire, Cuba, Cyprus, Czech Republic, the Democratic Republic of the Congo, Estonia, Finland, Georgia, Greece, Guyana, Hungary, India, Iran, Iraq, Italy, Kazakhstan, Kuwait, Kyrgyzstan, Latvia, Liberia, Lithuania, Macedonia, Moldova, Mongolia, Montenegro, Morocco, Netherlands, Nigeria, Norway, Pakistan, Paraguay, Philippines, Poland, Romania, Russia, San Marino, Senegal, Serbia, Seychelles, Sierra Leone, Slovakia, Slovenia, Sri Lanka, Tajikistan, Tunisia, Turkey, Turkmenistan, Ukraine, the United Arab Emirates, Uzbekistan and Vietnam.
The story of the Vienna Convention can be traced back to the 1909 International Convention on Motor Traffic in Paris. This dealt with all aspects of roads and traffic, but gave significant attention to the problem of the international standardisation of road signage and signals. Among the documents presented at the International Convention on Motor Traffic was the League of Nations Special Committee of Enquiry on Road Traffic. Another International Convention on Motor Traffic was held in 1926, but the problem of road signs and signals was not fully addressed on that occasion, so another special convention on the Unification of Road Signs was held in Geneva in 1931. One reason why America is not currently part of the Vienna Convention lies in the response to the 1926 and 1931 conventions. Rather than accept these, the Pan American Union in Washington instead issued their own Convention on the Regulation of Inter-American Automotive Traffic. In 1948 resolution 147 B (VII) of the United Nations Economic and Social Council was passed in response to the latter convention. It called for a new United Nations Conference on Road and Motor Transport to be convened. This in turn led to the 1949 Convention on Road Traffic and a Protocol on Road Signs and Signals.
In 1966 the United Nations Economic and Social Council issued resolution 1129 (XLI). Certain important points of detail in this document were, however, supplemented and replaced in resolution 1203 (XLII). Also two draft conventions were prepared as a basis for a new conference (E/CONF.56/1 and Addendum.1 and Correction.1 and E/CONF.56/3 and Addendum.1 and Correction.1). This very important convention was scheduled by the Economic and Social Council for the months of October and November in 1968. It was held in Vienna, which is why the resulting convention is called the Vienna Convention on Road Signs and Signals.
The Convention categorises road signs and signals into specific categories. These are: danger warning signs, priority signs, prohibitory or restrictive signs, mandatory signs, information, facilities or service signs, direction, position or indication signs and, finally, any additional panels that might be required in order to communicate information to drivers and other users of vehicles. Examples of danger warning signs include yield signs, stop signs, specific types of priority signs, end priority signs, priority for oncoming traffic signs and priority over oncoming traffic signs. Examples of prohibitory signs include standard prohibitory signs, parking prohibitory signs and end of prohibition signs.