The Convention on Road Signs and Signals, commonly known as the Vienna Convention on Road Signs and Signals, is a multilateral treaty that establishes an international standard for signing systems for road traffic, such as road signs, traffic lights and road markings. The Convention was agreed upon by the United Nations Economic and Social Council at its Conference on Road Traffic in Vienna, Austria from 7 October to 8 November 1968. Thirty-one countries signed the Convention on the final day of the conference, and it entered into force on 6 June 1978. This conference also produced the Vienna Convention on Road Traffic, which provides complementary standardising of international traffic laws.
History The origins of the Convention may be traced back to the International Convention on Motor Traffic concluded in Paris on 11 October 1909, which concerned motor vehicle construction, admission of international motor traffic, and road signs and signals. Commensurate with growing motor vehicle traffic, the 1909 convention was amended and expanded by two more treaties that were concluded in Paris on 24 April 1926: The International Convention relating to Road Traffic and the International Convention relating to Motor Traffic. As neither convention dealt exhaustively with road signs and signals, a Convention concerning the Unification of Road Signs was concluded in Geneva on 30 March 1931, which was expanded upon by the 1949 Convention on Road Traffic and a Protocol on Road Signs and Signals, likewise agreed upon in Geneva. Amid calls for greater international uniformity in road signing systems, the Vienna Convention on Road Signs and Signals was called to revise and substantially extend the earlier 1949 Geneva Protocol,. 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 U.S. 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, several Asian countries (Cambodia, Japan, Thailand, Malaysia and Indonesia) and New Zealand, road signage is influenced by both the Vienna Convention and MUTCD. Road signs in Central America 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 2025, the Global Forum for Road Traffic Safety (WP.1) adopted an amendment proposal, which will replace the entire text of the Convention. The proposal will also affect the European Supplement Agreement and the Protocol on Road Markings. Some major changes in the amendment are:
a new numbering scheme for the road signs the abolishment of the variant B, 2b for stop signs the abolishment of the variant for mandatory signs with red rim and black symbols the inclusion of the signs from the European Supplement Agreement into the convention some new signs (e.g. G-25.0) updated example images for all road signs The amendment will enter into force on 12 November 2026, except for Chile and the Netherlands, which rejected it.
Rules
Road signs In article 2 the convention classes all road signs into a number of categories (A–H):
A: Danger warning signs B: Priority signs C: Prohibitory or restrictive signs D: Mandatory signs E: Special regulation signs F: Information, facilities, or service signs G: Direction, position, or indication sign H: Additional panels The convention then lays out precise colours, sizes, and shapes for each of these classes of sign:
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.
Road markings 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".
Traffic lights 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.
Contracting parties As of 2026, 75 states are party to the Vienna Convention. This includes 35 of the original 37 signatories, 8 states which succeeded to the treaty following the dissolution of two of the signatories, and 44 states which acceded to the treaty after it was signed.
Signatory parties These states negotiated and signed the Convention between 1968 and 1969:
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