Most countries place signs, known as traffic signs or road signs, at the side of roads to impart information to motorists and other road users. Since language differences can create barriers to understanding, international signs using symbols in place of words have been developed in Europe and adopted in most countries and areas of the world. Annexe 1 of the Vienna Convention on Road Signs and Signals of November 8, 1968 defines eight categories of signs:
- 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 signs
- H. Additional panels
However, countries and areas categorize road signs in different ways.
The earliest road signs gave directions, for example the Romans erected stone columns throughout their empire giving the distance to Rome. In the Middle Ages multidirectional signs at intersections became common giving directions to cities and towns.
Traffic signs became more important with the development of automobiles. The basic patterns of most traffic signs were set at the 1908 International Road Congress in Rome. Since then there have been considerable change. Today they are almost all metal rather than wood and are coated in a thin film filled with small glass particles that make them highly reflective (see retroreflection).
United States of America
North America and Australia
In North America and Australia, signs generally adhere to the following colours:
- green with white letters for informational signs, such as directions, distances, and places
- brown with white for signs to parks, historic sites , ski areas, forests, and campgrounds
- blue with white for rest areas, food, gasoline or petrol, and lodging
- white with red or black letters for regulatory signs, such as speed limits or parking
- yellow with black letters and symbols for warning signs, such as curves and school zones
- orange with black letters for construction zones and detours
Regulatory signs are also sometimes seen with white letters on red or black signs. In Quebec, the usage of blue and brown is reversed, and many black-on-yellow signs are red-on-white instead. Many U.S. states now use fluorescent orange for construction signs, and fluorescent yellow-green (FYG) for school zone and crosswalk signs.
Every state and province has different markers for its own highways, but use standard ones for all federal highways. Many special highways, such as the Queen Elizabeth Way or Trans-Canada Highway, or originally on U.S. highways like the Dixie Highway, have used unique signs. Counties in the U.S. sometimes use a pentagon-shaped blue sign with yellow letters for numbered county roads, though the use is inconsistent even within states.
American road signs measure distances in miles rather than kilometres. Traffic signs in the United States have been standardized through the Manual on Uniform Traffic Control Devices (MUTCD), though they sometimes still vary from state to state, particularly on older signs.
Signs in most of Canada, the U.S. and Australia are written in English . Quebec uses French , while New Brunswick uses both English and French. Mexico uses Spanish . Within a mile of the U.S.-Mexico border, road signs are often in English and Spanish.
Despite efforts to devise pan-European standards, the European Union has not yet standardised road signs across member states, with non-member states also differing in road signage. All EU members currently use the metric system for road signs, with the exception of the UK
- Main article: Roads in Ireland
Until the partition of Ireland in 1922 and the independence of Southern Ireland (now the Republic of Ireland) British standards applied across the island. Some time after independence, road signs in the south were changed to differ from the UK standard, most visibly in the adoption of US-style "diamond" signs for many road hazard warnings (junctions, bends, railway crossings, traffic lights). Some domestic signs were also invented, such as the stay-left sign (a black curved arrow pointing to the upper-left), while some other signs are not widely adopted outside Ireland, such as the no-entry sign (a black arrow pointing ahead in a white circle with a red slashed circumference).
In general, the UK's signage is largely similar to that in the rest of Europe, though it has a large number of signs that are unique to the UK. In addition, the system and style of signage employed for route information is specific to the UK. Signs which predate WW2 are also still found, and these have a different standard again. Also, the UK is the only European Union member to use a system other than the metric system, i.e. imperial.
Pictured on the right is a road sign near Bristol in England, giving directions to Parkway railway station (red symbol), motorways (blue backgrounds) and A roads (major roads). The red outline is used for military establishments (the Ministry of Defence at Abbey Wood).
Central and South America
Road signs in Central and South America vary from country to country. For the most part, conventions in signage tend to resemble North American signage conventions more so than European and Asian conventions. For example, warning signs are typically diamond shaped and yellow rather than triangular and white. Some variations include the "No Parking" sign, which uses a letter 'E' instead of 'P' (the Spanish word for 'Parking' is 'Estacionar'). Notable exceptions include speed limit signs, which follow the European conventions.
People's Republic of China
Mainland China uses simplified Chinese characters for its traffic signs. It is gradually moving toward internationally-accepted signs; it abandoned, for example, a localised version of the "no parking sign" (with a Hanzi character) and used the blue-red cross sign as of the late 1990s.
In larger cities and on expressways of China, both English and Chinese are used.
Hong Kong Special Administrative Region
Although the mainland uses simplified Chinese characters, traditional Chinese characters are still used in Hong Kong (as the policy of "one country, two systems" allows Hong Kong to maintain most affairs, including road traffic regulations, the way they were prior to the handover).
Most, if not all, of Hong Kong's signs are bilingual, as English and Chinese are considered official languages. English often appears on top of text in traditional Chinese.
See also: Street sign theft