History

Roman milestone

The earliest road signs were milestones, giving distance or direction; 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 with retroreflective sheetings of various types for nighttime and low-light visibility.

New generations of traffic signs based on big electronic displays can also change its symbols and also provide intelligent behavior by means of sensors or by remote control. In this sense, “road beacons” (RBS) based in the use of RFID special transponders buried in the asphalt arise as an innovative evolution for on-board signalling.

Yet another "medium" for transferring information ordinarily associated with visible signs is RIAS (Remote Infrared Audible Signage), e.g. “Talking Signs” for print-handicapped (including blind/low-vision/illiterate) people. These are infra-red transmitters serving the same purpose as the usual graphic signs when received by an appropriate device such as a hand-held receiver or one built into a cell phone.

Europe

In 1968, the European countries signed the Vienna Convention on Road Traffic treaty, the aim of which was to standardize traffic regulations in participating countries in order to facilitate international road traffic and to increase road safety. Part of the treaty was the Vienna Convention on Road Signs and Signals, which defined the traffic signs and signals. As a result, in Western Europe the traffic signs are well standardized nowadays, although there are still some country-specific exceptions in many countries, mostly dating from the pre-1968 era. The convention has been adapted to allow variations when countries weren’t expected to follow the main standard.

The basic principle of the European traffic sign standard is that usage of certain shapes and colours are to be used systematically for indicating the same purposes. Triangular shapes (white or yellow background) are used in warning signs. Additionally, the Vienna convention allows an alternative shape for warning signs, a diamond shape, which is rarely used in Europe. The prohibition signs in Europe are round with a red border. Informative and various other secondary signs are of rectangular shape. With the animal warning signs, one can notice national flavour quite often, with symbols of moose, frog, deer, cow, etc., even Polar bear in Svalbard and monkey in Gibraltar, and the Convention allows any animal to be used.

Directional signs have not been harmonised under the Convention, at least not on ordinary roads. As a result, there are substantial differences in directional signage throughout Europe. Differences apply in typeface, type of arrows and, most notably, colour scheme. The convention however specifies a difference between motorways and ordinary roads, and that motorways use white-on-green (e.g. Italy, Switzerland, Denmark, Sweden, Finland, Slovenia, Croatia, Czech Republic, Slovakia) or white-on-blue (e.g. Germany, the Republic of Ireland, France, United Kingdom, Spain, Netherlands, Belgium, Austria, Luxembourg, Poland, Portugal).

Differences are greater for non-motorways: white-on-blue in Italy, Switzerland, Sweden, Slovakia, Finland and Netherlands (in this case the same as motorways), white-on-green in France, United Kingdom, Poland and Portugal, black-on-yellow in Germany, Luxembourg, Norway, Slovenia and Croatia, red-on-white in Denmark (though white-on-blue on motorway exits), and black-on-white in Spain. Other nations split among the non-motorways.

Secondary roads are different from primary roads in France, United Kingdom, Finland, Republic of Ireland, Switzerland and Portugal, always signposted in black-on-white. In Italy and Sweden, black-on-white indicates only urban roads or urban destinations.

Signposting road numbers differs greatly as well. Only the European route number, if signposted, will always be placed in white letters on a green rectangle.

The languages to be used are according to the convention the language(s) of the individual country. Some signs like “STOP”, “ZONE” etc. are recommended to be in English, but the local language is also permitted. If the language uses non-Latin characters, the names of cities and places should also be in Latin transcription.

European countries use the metric system on road signs (distances in kilometres or metres, heights/widths in metres) with the notable exception of the UK, where distances are still indicated in miles. For countries driving on the left, the convention stipulates that the traffic signs should be mirror images of those used in countries driving on the right. This practice, however, is not systematically followed in the two European countries driving on the left, the Republic of Ireland and the United Kingdom. The convention permits the usage of two background colours for danger and prohibitory signs, white or yellow. Most countries use white with a few exceptions like Sweden, Finland, Iceland and Poland, for instance, where the yellow colour was chosen.