Vienna Convention on Road Signs and Signals

The Convention on Road Signs and Signals, commonly known as the Vienna Convention on Road Signs and Signals, is a multilateral treaty to standardize the signing system for road traffic (road signs, traffic lights and road markings) in use internationally.
This convention was agreed upon by the United Nations Economic and Social Council at its Conference on Road Traffic in Vienna 7 October to 8 November 1968, was concluded in Vienna on 8 November 1968, and entered into force on 6 June 1978. This conference also produced the Vienna Convention on Road Traffic, which complements this legislation by standardising international traffic laws.
The convention revised and substantially extended the earlier 1949 Geneva Protocol on Road Signs and Signals, itself based in turn on the 1931 Geneva Convention concerning the Unification of Road Signals. Amendments, including new provisions regarding the legibility of signs, priority at roundabouts, and new signs to improve safety in tunnels were adopted in 2003.
Both the Vienna Convention and the Geneva Protocol were formed according to consensus on road traffic signs that evolved primarily in 20th century continental Western Europe. In order to make it as universal as possible, the convention allows some variations, for example danger warning signs can be triangular or square diamond in shape and road markings can be white or yellow. Though most UN members have not ratified the full treaty, the signs and legal principles enshrined in it form the basis of traffic law in a majority of places.
An alternative convention called the SADC-RTSM, provided by the Southern African Development Community (SADC), is used by ten countries in southern Africa. Many of the rules and principles of the SADC-RTSM are similar to those of the Vienna Convention.
In the United States, signs are based on the US Federal Highway Administration's Manual on Uniform Traffic Control Devices. Signs in the MUTCD are often more text-oriented, though some signs do use pictograms as well. Canada and Australia have road signs based substantially on the MUTCD. In South America, Ireland, several Asian countries (Cambodia, Japan, Thailand, Malaysia and Indonesia) and New Zealand, road signage is influenced by both the Vienna Convention and MUTCD. In Central America, road signs are heavily influenced by MUTCD and based on the Manual Centroamericano de Dispositivos Uniformes para el Control del Transito, a Central American Integration System (SICA) equivalent to the US MUTCD.
In article 2 the convention classes all road signs into a number of categories (A–H):
The convention then lays out precise colours, sizes, and shapes for each of these classes of sign:
May be written in English or the national language
It also specifies the symbols and pictograms which may be used, and the orientations in which they may be used. When more than one is available, the same one must be used nationally. All signs, except for those that do not apply at night, must be reflective enough to be seen in darkness with headlights from a distance.
The convention also specifies road markings. All such markings must be less than 6 mm high, with cat's eye reflectors no more than 15 mm above the road surface. The road markings shall be white or yellow.
The length and width of markings varies according to purpose, although no exact figures for size are stated; roads in built up areas should use a broken line for lane division, while continuous lines must only be used in special cases, such as reduced visibility or narrowed carriageways.
All words painted on the road surface should be either of place names, or of words recognisable in most languages, such as "Stop" or "Taxi".
The Convention specifies the colours for traffic lights and their meanings, and places and purposes lights may be used for, like so:
Red flashing lights may only be used at the locations specified above; any other use of the lights is in breach of the convention. Red lights must be placed on top when lights are stacked vertically, or on the side closest to oncoming traffic if stacked horizontally.
The convention has 71 state parties and 35 signatories (including acceding members) as of October 2022: Albania, Armenia, Austria, Azerbaijan, Bahrain, Belarus, Belgium, Benin, Bosnia and Herzegovina, Brazil, Bulgaria, Burundi, Central African Republic, Chile, Costa Rica, Côte d'Ivoire, Croatia, Cuba, Cyprus, Czechia, Democratic Republic of the Congo, Denmark, Ecuador, Estonia, Finland, France, Georgia, Germany, Ghana, Greece, Guyana, Holy See, Hungary, India, Indonesia, Iran, Iraq, Italy, Kazakhstan, Kuwait, Kyrgyzstan, Latvia, Liberia, Liechtenstein, Lithuania, Luxembourg, North Macedonia, Madagascar, Mexico, Moldova, Mongolia, Montenegro, Morocco, Myanmar, Netherlands, Nigeria, Norway, Pakistan, Paraguay, the Philippines, Poland, Portugal, Qatar, Romania, Russia, San Marino, Saudi Arabia, Senegal, Serbia, Seychelles, Sierra Leone, Slovakia, Slovenia, Spain, Sri Lanka, Suriname, Sweden, Switzerland, Tajikistan, Thailand, Tunisia, Turkmenistan, Uganda, Ukraine, United Arab Emirates, United Kingdom, Uzbekistan, Venezuela and Vietnam.
The only countries in Europe that are not parties to the convention are Andorra, Ireland, Iceland, Malta and Monaco.
Countries in Asia that are not parties to the convention are Afghanistan, Bangladesh, Malaysia, People's Republic of China (including Hong Kong and Macau), Republic of China (Taiwan), Israel, Japan, Jordan, Lebanon, North Korea, Oman, Palestine, Syria and Yemen. Cambodia, Laos, and South Korea are all signatories, but have yet to ratify the convention.
Other countries have not signed the convention; however, some have voluntarily adopted some Vienna convention signs.