- Traffic sign
Most countries post signage, known as traffic signs or road signs, at the side of
roads to impart information to road users. Since language differences can create barriers to understanding, international signs using symbols in place of words have been developed in Europeand adopted in most countries of the world.
Anexe 1 of the
Vienna Convention on Road Signs and Signalsof November 8 1968defines eight categories of signs:
*C. Prohibitory or restrictive signs
Special regulation signs
*F. Information, facilities, or service signs
Direction, position, or indication signs
*H. Additional panelsHowever, countries and areas categorise road signs in different ways. In the U.S., the type, placement, and graphic standards of traffic signs and pavement markings are legally defined — the
Federal Highway Administration's " Manual on Uniform Traffic Control Devices" is the standard.
A rather informal distinction among the directional signs is the one between advance directional signs, interchange directional signs and reassurance signs. Advance directional signs will appear at a certain distance from the interchange, giving information for each direction. A number of countries do not give information for the road ahead (so-called pull-through signs) though, and only for the directions left and right. Advance directional signs enable drivers to take precautions for the exit (i.e., switch lanes, double check whether this is the correct exit, slow down). They will often not appear on lesser roads, but are more or less mandatory on expressways and motorways, as drivers would be missing exits without them. While each nation has its own system, the first approach sign for a motorway exit is mostly placed at least 1000 m from the actual interchange. After that sign, one or two additional advance directional signs would typically follow before the actual interchange itself.
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 Agesmultidirectional signs at intersections became common, giving directions to cities and towns.
Traffic signs became more important with the development of automobiles. One of the first modern-day road sign systems was devised by the Italian Touring Club in 1895. By 1900, a Congress of the International League of Touring Organizations in Paris was considering proposals for standardization of road signage. The basic patterns of most traffic signs were set at the 1908
International Road Congressin Rome. In 1909, nine European governments agreed on the use of four pictorial symbols indicating "bump," "curve," "intersection" and "grade-level railroad crossing." The intensive work on international road signs that took place between 1926 and 1949 eventually led to the development of the European Road Signs system. The United States developed its own road signage system, which was also adopted by several other nations. Beginning in the 1960s, North American signage began adopting international symbols and signs into its system.
Over the years, change was gradual. Today signs 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 their symbols and provide intelligent behavior by means of sensors or by remote control. These "road beacon systems" (RBS) are based on the use of RFID transponders buried in the asphalt to allow for on-board signalling and interaction between the car and the road.
Yet another "medium" for transferring information ordinarily associated with visible signs is
RIAS (Remote Infrared Audible Signage), e.g., [http://www.talkingsigns.com "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.
North America and Australia
* Guide signs
**Route marker signs
Recreationand cultural interest signs
Emergency management( civil defense) signs
Temporary traffic control( constructionor work zone) signs
Railroadand light railsigns
North American, Australian and New Zealandcolours normally have these meanings:
redwith white for stop signs, yield, and forbidden actions (such as No Parking)
greenwith white letters for informational signs, such as directions, distances, and places
brownwith white for signs to parks, historic sites, ski areas, forests, and campgrounds
bluewith white for rest areas, food, gasolineor petrol, hospitals, lodging, and other services
blackwith whitefor commercial, exempt, special, and signs were used in the past
whitewith black(or redletters) for regulatory signs, such as speed limits (or parking)
yellowwith black letters and symbols for warning signs, such as curves and school zones
*orange with black letters for temporary traffic control zones and
detours associated with road construction
Regulatory signs are also sometimes seen with white letters on red or black signs. In
Quebec, blue is often used for tourist attractions and brown public services such as rest areas; many black-on-yellow signs are red-on-white instead. Many U.S. statesand Canadian provinces now use fluorescentorange for construction signs, and fluorescent yellow-green for school zone, crosswalk, pedestrian, and bicycle warning signs. Fluorescentpink signs are sometimes used for incident management warning.
Highway symbols and markers
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 Wayor 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.
Most U.S. road signs measure distances in miles rather than kilometers although the federal Department of Transportation has developed metric standards for all signs. United Kingdom signs also display distances in miles. Generally, elsewhere, distances are in metric.
Signs in most of Canada, the U.S., Australia, and New Zealand are written in English. Quebec uses French, while
New Brunswickuses both English and French and a number of other provinces such as Ontarioand Manitobause bilingual French-English signs in certain localities. Mexicouses Spanish. Within a few miles of the U.S.-Mexico border, road signs are often in English and Spanish, and indigenous languages, mainly Nahuatlas well as some Mayan languages, have been used as well.
The typefaces predominantly used on signs in the U.S. and Canada are the FHWA alphabet series (Series B through Series F and Series E Modified). Details of letter shape and spacing for these alphabet series are given in "Standard Alphabets for Traffic Control Devices," first published by the
Bureau of Public Roads(BPR) in 1945 and subsequently updated by the Federal Highway Administration(FHWA). It is now part of Standard Highway Signs(SHS), the companion volume to the MUTCD which gives full design details for signfaces.
Initially, all of the alphabet series consisted of uppercase letters and digits only, although lowercase extensions were provided for each alphabet series in a 2002 revision of SHS. Series B through Series F evolved from identically named alphabet series which were introduced in 1927.
Straight-stroke letters in the 1927 series were substantially similar to their modern equivalents, but unrounded glyphs were used for letters such as B, C, D, etc., to permit more uniform fabrication of signs by illiterate painters. Various state highway departments and the federal BPR experimented with rounded versions of these letters in the following two decades.
The modern, rounded alphabet series were finally standardised in 1945 after rounded versions of some letters (with widths loosely appropriate for Series C or D) were specified as an option in the 1935 MUTCD and draft versions of the new typefaces had been used in 1942 for guide signs on the newly constructed
Pentagon road network.
The mixed-case alphabet now called Series E Modified, which is the standard for destination legend on freeway guide signs, originally existed in two parts: an all-uppercase Series E Modified, which was essentially similar to Series E except for a larger stroke width, and a lowercase-only alphabet. Both parts were developed by the California Division of Highways (now
Caltrans) for use on freeways in 1948-50.
Initially the Division used all-uppercase Series E Modified for button-reflectorized letters on ground-mounted signs and mixed-case legend (lowercase letters with Series D capitals) for externally illuminated overhead guide signs. Several Eastern turnpike authorities blended all-uppercase Series E Modified with the lowercase alphabet for destination legends on their guide signs.
Eventually this combination was accepted for destination legend in the first manual for signing Interstate highways, which was published in 1958 by the American Association of State Highway Officials (AASHO) and adopted as the national standard by the BPR.
Uses of Non-FHWA Typefaces
National Park Serviceuses NPS Rawlinson Roadway, a seriftypeface, for guide signage (typically, but not always, on a brown background). Rawlinson has replaced Clarendon as the official NPS typeface, but some states still use Clarendon for recreational signage.
Georgia, in the past, used uppercase Series D with a custom lowercase alphabet on its freeway guide signs; the most distinctive feature of this typeface is the lack of a dot on lowercase "i" and "j". [http://www.gribblenation.com/gapics/gallery/i20w-exit60-natsiatka.jpg] More recent installations appear to include the dots. [http://www.gribblenation.com/gapics/gallery/albany-exit2-3-natsiatka.jpg]
A new typeface family titled "Clearview" has been developed by U.S. researchers in recent years to provide improved legibility, and is permitted for light legend on dark backgrounds under FHWA interim approval. Clearview has only seen widespread use by state departments of transportation in
Arkansas, Illinois, [ [http://www.dot.state.il.us/press/r101106.html Illinois Department of Transportation ] ] Michigan, Pennsylvania, Texasand Virginia. In Canada, the Ministry of Transportation for the Province of British Columbiaspecifies Clearview for use on its highway guide signs, [ [http://www.th.gov.bc.ca/popular-topics/faq.htm#general 2006 Internet Templates ] ] and its usage has shown up in Torontoon the Don Valley Parkwayand Gardiner Expressway, as well as major city streets (white on blue). The Clearview font is also being used on newer signs in Manitoba.
It is common for local governments, airport authorities, and contractors to fabricate traffic signs using typefaces other than the FHWA series;
Helveticaand Arialare common choices.
1935-11-01, six blue-white danger warning signs. They were supplanted after 1939-11-01with red-white-black signs.] In 1968, the European countries signed the Vienna Convention on Road Traffictreaty, with the aim of standardizing 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 standardised, although there are still some country-specific exceptions, mostly dating from the pre-1968 era.
The principle of the European traffic sign standard is that shapes and colours are to be used for indicating 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. Animals shown on warning signs include moose, frogs, deer, ducks, cows, sheep, horses,
polar bears (on Svalbard), and monkeys (in Gibraltar). The Convention allows any animal image 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, Greece, Cyprus, Romania, Slovakia, Serbia) or white-on-blue (e.g., Germany, the Republic of Ireland, France, United Kingdom, Spain, Netherlands, Belgium, Austria, Luxembourg, Poland, Portugal, Latvia). Hungaryswitched from white-on-green to white-on-blue in the early 2000s during the reconstruction of existing and construction of new motorways, although the first section of the M5 motorway built in the early 90s still has white-on-green signes.
Differences are greater for non-motorways: white-on-blue in
Italy, Switzerland, Sweden, Czech Republic, Greece, Cyprus, Slovakia, Romania, Latvia, Finlandand Netherlands(in this case the same as motorways), white-on-green in France, United Kingdom, Republic of Ireland, Polandand Portugal, black-on-yellow in Germany, Luxembourg, Norway, Slovenia, Serbiaand Croatia, red-on-white in Denmark(though white-on-blue on motorway exits and all overhead gantries), and black-on-white in Spain.
Secondary roads are different from primary roads in
France, United Kingdom, Finland, Republic of Ireland, Switzerlandand Portugal, always signposted in black-on-white. In Germany, Italy, Romaniaand 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. European route numbers are not signed at all in the United Kingdomand are signed only on one recent scheme in the Republic of Ireland.
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.Road signs in the
Republic of Irelandare bilingual, using Irish and English. Walesis also the same, with bilingual Welsh-English signs; some parts of Scotlandalso have bilingual Scottish Gaelic-English signs. Also Finlanduses bilingual signs, in Finnish - Swedish.
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, and on remaining finger post signs in the
Republic of Irelanderected before 1977, where distances are also indicated in miles (which were formally used for all directional signage in the Republic of Ireland prior to 1977 and on speed limits prior to 2005). 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 four European countries driving on the left, Cyprus, the Republic of Ireland, Maltaand the United Kingdom. The convention permits the use of two background colours for danger and prohibit signs, white or yellow. Most countries use white with a few exceptions like Sweden, Finland, Icelandand Poland.
The European traffic signs have been designed with the principles of
heraldryon mind; i.e., the sign must be clear and able to be resolved with one single glance. Most traffic signs conform to heraldic tincture rules, and rather use symbols than written texts for better semiotic clarity.
Traffic signing in the UK conforms broadly to European norms, though a number of signs are unique to Britain and direction signs omit European route numbers. The current sign system, introduced on
1 January 1965, was developed in the late 1950s and early 1960s by the Anderson Committee, which established the motorwaysigning system, and by the Worboys Committee, which reformed signing for existing all-purpose roads. ( For illustrations of most British road signs see the [http://www.highwaycode.gov.uk/signs_index.htm Highway Code website] )
Britain remains the only
European Unionmember nation and the only Commonwealth country to use non-metric (Imperial) measurements for distance and speed, although metric "authorised-weight" signs were prescribed in 1981 and there is now a dual-unit (imperial first) option for restriction signage, used on safety grounds where foreign drivers may use the routes so that they may better understand the restriction and / or advice about a hazard ahead.
Three colour schemes exist for direction signs. A road may be a motorway (white on blue), a primary route (white on dark green with yellow route numbers), or a non-primary route (black on white). Most
trunk roads, which carry most of the vehicular traffic and are owned by and maintained by the Highways Agency, other roads are maintained by local authorities, for example county or borough councils (borough councils are still subservient to the county in regards to highway matters but act as their agents in maintenance)
typefaces are specified for British road signs. Transport "medium" or Transport "Heavy" are used for all text on fixed permanent signs and most temporary signage, depending on the color of the sign and associated text color, white text on a dark background is normally "heavy" so that it stands out better. This is except for route numbers on motorway signs for which a taller limited character set typeface called Motorway is used.
Signs are generally in English although
bilingual signs are used in Wales(English/Welsh) and are beginning to be seen in parts of the Scottish Highlands(English/Scottish Gaelic), some translate very questionably see [http://www.threecockshotel.com/findus.htm]
All signs and their associated regulations can be found in "The Traffic Signs Regulations and General directions "2002" (currently) " also known as TSRDG, this can be found at [http://www.opsi.gov.uk/si/si2002/20023113.htm] and also other rules / regulations apply from the Highways Act, related to the
Road signs in The Netherlands follow the Vienna Convention. Directional signs (which have not been harmonised under the Convention) always use blue as the background colour. The destinations on the sign are printed in white. If the destination is not a town (but an area within town or some other kind of attraction), that destination will be printed in black on a separate white background within the otherwise blue sign.
The Netherlands always signpost European road numbers where applicable (i.e., on the advance directional signs, the interchange direction signs and on the
reassurance signs). Dutch national road numbers are placed on a rectangle, with motorways being signposted in white on a red rectangle (as an Axx) and primary roads in black on a yellow rectangle (as Nxx). When a motorway changes to a primary road, its number remains the same, but the A is replaced by the N. So at a certain point the A2 becomes N2, and when it changes to a motorway again, it becomes A2 again.
Signs intended for bike-riders always go on white signs with red or green letters.
The Dutch typeface, known as ANWB-Ee, is based on the US typeface. A new font, named ANWB-Uu (also known as Redesign), has been developed in 1997 and appears on many recent Dutch signs. The language of the signs is typically Dutch, even though bilingual signs may be used, when the information is relevant for tourists.
The road signs in Sweden mostly follow the Vienna Convention with a few adaptations, however, allowed within the convention:
* the background of warning and propitiatory signs is yellow
* the warning signs of moose and reindeer
* the background of direction signs is blue with white text
* the background of motorway direction signs is green with white text
* when applicable, the language of text is Swedish in Sweden.
The signage typeface
Tratexis used exclusively in Sweden and is available as freeware. [ [http://www.vv.se/templates/page3____2789.aspx Teckensnitt på vägmärken / Vägverket ] ]
Traffic signs in
Croatiaare the same as traffic signs in the rest of the former Yugoslavia. Croatian road signs appear to follow the Vienna convention. The most common signs are yellow and black signs "for direction", blue and white signs "for information" and white-on-green signs are used on the highways.
Until the partition of
Irelandin 1922 and the independence of Southern Ireland(now the Republic of Ireland) British standards applied across the island. In 1926 road sign standards similar to those used in the UK at the time were adopted. [ [http://www.irishstatutebook.ie/ZZSI55Y1926.html S.I. No. 55/1926: Road Signs and Traffic Signals Regulations, 1926] - Irish Statute Book] Law requires that the signs be written in both Irish and English .
In 1956, road signs in the Republic were changed to markedly differ from the UK standard with the adoption of US-style "diamond" signs for many road hazard warnings (junctions, bends, railway crossings, traffic lights). [ [http://www.irishstatutebook.ie/ZZSI284Y1956.html S.I. No. 284/1956: Traffic Signs Regulations, 1956] - Irish Statute Book] Some domestic signs were also invented, such as the keep-left sign (a black curved arrow pointing to the upper-left, although some are similar to the European "white arrow on blue disk" signs), 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).
Directional signage is still firmly based on the United Kingdom standard, however, with the basic design of directional signs remaining the same as the UK in most cases. The same colours are used for directional signs in Ireland as in the UK, and the UK Transport and Motorway fonts are used. However, signage in the Republic of Ireland is bilingual, with the Irish text in mixed case italics, while the English text is in all upper-case.
This also mostly refers to all the former republics of the USSR.
In January 2005 Ireland adopted metric speed limits. Around 35,000 existing signs were replaced and a further 23,000 new signs erected bearing the speed limit in kilometres per hour. To avoid confusion with the old signs, each speed limit sign now has "km/h" beneath the numerals. Also, since the adoption of signs based on the "Warboys Committee" standard in 1977, Irish directional signs have used the metric system, however, unlike with the later speed limit change over, there was no effort made to change the existing signage, and
as of 2007many finger posts still remain on rural roads with distances in miles, although the numbers continue to decline as roads are improved.
Road signs in Iceland mainly follow the
Vienna Convention, but use a variant of the colour scheme and minor design changes.
Road signs in Latvia mainly of
Vienna Conventionregulations, only the design is different from many other European countries. The signs have many design issues common with Russian road signs since the times of USSR.
outh and Central America
Road signs in South America and Central 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 'Estacionamiento'), as well as the Stop sign, which usually reads "Pare" or "Alto". Notable exceptions include speed limit signs, which follow the European conventions, and the "No Entry" sign, often replaced with a crossed upwards arrow.
Traffic signs in Colombia are classified into three categories. These are Warning signs, Mandatory signs and Information signs.
Warning signs are very similar to warning signs in United States. They are yellow diamond shaped with a black symbol (the yellow color is changed to an orange color in areas under construction). In certain cases, the yellow color is shifted to fluorescent yellow (in the School area sign and Chevron sign).
Mandatory signs are similar to European signs. They are circular with a red border, a white background and a black symbol. Stop sign and Yield sign are as European, except the word “Stop” is changed for “Pare” and the Yield sign has no letters, it is a red triangle with white center.
Information signs have many shapes and colors. Principally they are blue with white symbols and in many cases these signs have an information letter below the symbol.
[http://www.mintransporte.gov.co/Servicios/Biblioteca/documentos/Manual_senalizacion/index.htm Colombia traffic signs manual]
New Zealandroad signs pull in two directions, following both American and European practices.
Warning signs are diamond shaped with a yellow background for permanent warnings, and an orange background for temporary warnings. They are somewhat more pictorial than their American counterparts. Regulatory signs follow European practice, with a white circle with a red border indicating prohibitive actions, and a blue circle indicating mandatory actions. White rectangular signs with a red border indicate lane usage directions.Information and direction signs are rectangular, with a green background indicating a
state highway, a blue background for all other roads and all services (except in some, where directional signage is white), and a brown background for tourist attractions.
Before 1987, most road signs had black backgrounds - diamonds indicated warnings, and rectangles indicated regulatory actions (with the exception of the Give Way sign (an inverted trapezium), and Stop sign and speed limit signs (which were the same as today)). Information signs were yellow, and direction signage was green on motorways and black everywhere else.
Opel Insigniawill be the first production carto feature a dual-function frontal camera with traffic sign recognition.
Off-network tactical diversion route
Rules of the road
Street sign theft
Public signage typefaces
Comparison of European traffic signs
* [http://www.funnysign.com A gallery of strange signs from around the U.S.]
* [http://www.trafficsign.us/ Manual of Traffic Signs] – information on United States signs
* [http://mutcd.fhwa.dot.gov/HTM/2003r1/part2/part2-toc.htm Part 2: Signs] from the
Manual on Uniform Traffic Control Devices
* [http://www.quia.com/quiz/865512.html Traffic & Road Sign Test] – test your knowledge on U.S. traffic signs
* [http://www.mtqsignalisation.mtq.gouv.qc.ca Government of Quebec traffic control devices library] - Extensive list of all road signs and signals from the Quebec Transport Ministry "(in French and English)".
* [http://www.mto.gov.on.ca/english/traveller/signs/index.html Road Signs in Ontario] , from the Ontario Ministry of Transportation.
* [http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/Signsandmarkings/index.htm Signs and markings] British traffic signs from the
* [http://www.trafikken.dk/wimpdoc.asp?page=document&objno=14646#Danske_faerdselstavler Danish traffic signs]
* [http://www1.securiteroutiere.gouv.fr/signaux/default.asp Official French Government guide to road signs and signals] ("in French")
* [http://europa.eu.int/comm/transport/road/publications/trafficrules/countryreports/chapter7.htm Signs and signals in the European Union]
* [http://www.indiandrivingschools.com/road-traffic-signs-signals.html Indian Traffic Rules and Signals]
* [http://www.td.gov.hk/road_safety/road_users_code/index/chapter_8_the_language_of_the_road/ The Road User's Code: The Language of the Road] by the Transport Department of the Government of the Hong Kong SAR
* [http://www.mycrazyhobby.com A collection of street signs and traffic lights]
* [http://www.brombeer.net/signs Photos of directional signage on motorways]
* [http://www.nn.hr/clanci/sluzbeno/2003/0450.htm Traffic signs in Croatia]
Wikimedia Foundation. 2010.
Look at other dictionaries:
traffic sign — noun A sign for the control of traffic or the information of drivers. The traffic signs on motorways are particularly clear and well lit at night … Wiktionary
traffic sign — signpost, road sign, sign for directing traffic … English contemporary dictionary
traffic sign — noun : a sign usually on the side of a street or highway bearing symbols or words of warning or direction to motorists or pedestrians and often having a characteristic shape compare stop sign … Useful english dictionary
Traffic sign recognition — is a technology by which a vehicle is able to recognise the traffic signs put on the road e.g. slow or school ahead or turn ahead . This is part of the features collectively called ADAS. The idea is to improve road safety by assisting the driver … Wikipedia
Traffic sign design — Any tasks involved in the process of designing a traffic sign. Traffic signs give you important information about the law, warn you about dangerous conditions and help you find your way. These signs vary depending upon their use; they use… … Wikipedia
Prohibitory traffic sign — Prohibitory traffic signs Prohibitory traffic signs are used to prohibit certain types of manoeuvres or some types of traffic. Contents 1 Prohibitory traffic signs … Wikipedia
Traffic — on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel. Traffic laws are the laws which govern traffic and regulate… … Wikipedia
Traffic code — (also motor vehicle code) refers to the collection of local statutes, regulations, ordinances and rules that have been officially adopted in the United States to govern the orderly operation and interaction of motor vehicles, bicycles,… … Wikipedia
sign post — traffic sign, guidepost … English contemporary dictionary
Sign — A sign is an entity which signifies another entity. A natural sign is an entity which bears a causal relation to the signified entity, as thunder is a sign of storm. A conventional sign signifies by agreement, as a full stop signifies the end of… … Wikipedia