Warning sign
A warning sign is a type of sign which indicates a potential hazard, obstacle or condition requiring special attention. Some are traffic signs that indicate hazards on roads that may not be readily apparent to a driver.
While warning traffic sign designs vary, they usually take the shape of an equilateral triangle with a white background and thick red border. In the People's Republic of China, they appear with a black border and a yellow background. In Sweden, Serbia, Bosnia and Herzegovina, Greece, Finland, Iceland, North Macedonia and Poland, they have a red border with an amber background. The polar bear warning sign in Svalbard recently changed from displaying a black bear on white background to a white bear on black background. Some countries that normally use a white background have adopted an orange or amber background for road work or construction signs.
Warning signs in some countries have a diamond shape in place of the standard triangular shape. In the United States, Canada, Mexico, Thailand, Australia, Japan, Indonesia, Malaysia, New Zealand, most of South America, and also Ireland use warning signs are black on a yellow background and usually diamond-shaped, while temporary signs are black on an orange background. Some other countries also use these standards for some signage.
The warning signs usually contain a symbol. In Europe they are based on the UNECE Vienna Convention on Road Signs and Signals. In the United States they are based on the MUTCD standard and often contain text only.
History
Some of the first roadside signs—ancient milestones—merely gave distance measures. Hazard warnings were rare though occasional specimens appeared, such as the specific warning about horse-drawn vehicles backing up which was carved in stone in Lisbon's Alfama neighborhood in 1686. The early signs did not have high-contrast lettering and their messages might have been easily overlooked. Signs were written in the local language ; symbolic signs, though long used on certain tradesmen's signs were to be used for traffic only much later in history.Complex signage systems emerged with the appearance of motorcars. In 1908 the automobile association in West London erected some warning signs. In 1909, nine European governments agreed on the use of four pictorial symbols, indicating bump, curve, intersection, and 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 sign system.
As the 20th century progressed, and traffic volume and vehicle speeds increased, so did the importance of road sign visibility. Earlier flat-painted signs gave way to, which in turn gave way to button copy signs—round retroreflective "buttons" helped to achieve greater night visibility. Flat metal signs reappeared in the 1980s with the widespread use of surfaces covered with retroflective sheeting materials like Scotchlite.
In Europe, the 1968 Vienna Convention on Road Signs and Signals tried, among other things, to standardize important signs. After the fall of the Iron Curtain and greater ease of country-to-country driving in the EU, European countries moved toward lessening the regional differences in warning signs.
In modern regulations, U.S. warning signs are classified as Series W signs, such as: W1 Series, W2 Series, W22 Series, et cetera, ending with the W25 Series. Some U.S. warning signs are without category while others like the warning stripes at tunnel portals or plain red End of Roadway signs are classified as Object Markers. In the U.S., Stop and speed limit signs fall under the R Series. Modern U.S. signs are widely standardized; unless they are antique holdovers from an earlier era, oddities like a yellow Stop sign or a red Slippery When Wet sign would typically appear only on private property—perhaps at a hospital campus or in a shopping mall parking lot.
Street sign theft by pranksters, souvenir hunters, and scrappers has become problematic: removal of warning signs costs municipalities money to replace lost signs, and can contribute to traffic collisions. Some authorities affix :File:Streetsign theft warning.jpg|theft-deterrence stickers to the back sides of signs. Some jurisdictions have criminalized unauthorized possession of road signs or have outlawed their resale to scrap metal dealers. In some cases, thieves whose sign-removal lead to road fatalities have been charged with manslaughter. Artistically inclined vandals sometimes paint additional details onto warning signs: a beer bottle, a handgun, or a boom box added to the outstretched hand of the Pedestrian Crossing person, for example.
Modern traffic warning sign shapes and colors
Warning signs can indicate any potential hazard, obstacle or condition requiring special attention. Some of the most common warning signs are the following.General caution
General warning signs are used in instances in which the particular hazard, obstacle or condition is not covered by a standard sign. In Europe, they usually comprise an exclamation mark on the standard triangular sign with an auxiliary sign below in the local language identifying the hazard, obstacle or condition. In Sweden, the general warning sign has only a vertical line instead of exclamation mark; this model was used also in many other European countries until the 1990s. In the United States and other countries using diamond-shaped signs, the explanatory language is often written directly on the diamond-shaped sign, although it may contain only a general warning such as "Caution", and pictograms may also be used.Obstacles
Warning signs can be placed in advance of, next to or on a specific obstacle. Obstacles such as railway level crossings may have several warning signs beforehand, while bridge ramparts typically have reflective signs placed directly on them on either side. These signs can be specific to the shape requirements of the obstacle, for example, bridge rampart signs are often tall and skinny so as not to intrude into the lane.Animals crossing the roadway
These signs warn of wild animals or farm animals that may stray onto the road. In the United States, a "share the road" plaque is sometimes placed below these warning signs when used in this manner.Unusual vehicles in roadway
These signs are found where road users could encounter slow, large or non-typical vehicle such as tractors, forklifts, snowmobiles, Amish buggies etc. They are more common around quarries, airports, industrial zones and rural areas.Road work or construction
These signs are often temporary in nature and used to indicate road work, poor roads, or temporary conditions ahead on the road including: flagmen, survey crew, single-lane, detour, bridge out, utility crew ahead, blasting area, bump, dip, frost heaves, flooding, soft shoulder, uneven pavement, freshly oiled road, loose gravel, smoke on road, trucks entering, etc. In France, Italy, Spain, Norway etc., warning signs connected with road work have a yellow background in place of the usual white background on signs. In America and Ireland, signs connected with road work have an orange background.Curves and corners
These signs indicate that dangerous or unexpected bends in the road are ahead. Signs typically indicate whether the curves are to the right or to the left, the angle of the curve and whether it is one curve or a series of curves.Chevrons and arrows
-shaped symbols or arrows on rectangular signs may be placed at the actual location of the bend or curve to further mark the location of the curve and to assist in the negotiation of the curve. They may also be used to indicate "merge" with other traffic, as for an on-ramp of a limited-access highway.An unusual occurrence of the rectangular arrow sign appears on the eastbound approach to Dead Man's Curve in Cleveland, Ohio, USA, a curve so sharp that in places an arrow's stem is printed on one sign and the arrow's point is printed on another larger sign further down the road; from the driver's perspective at a distance the two signs visually blend together to form one large arrow image.
Tunnels
These signs are used to indicate tunnels, where lights are usually required, and a general change in the light level. May also indicate low ceiling clearance. Truck drivers should also watch for prohibited cargo signs upon approach to tunnels.Bridges
These signs are used where traffic may be constricted to a narrow bridge, or where the bridge may have a movable span closed to vehicles while boats pass. They may also be used for underpass to indicate low overhead clearance.Traffic signals
These warning signs indicate that traffic lights are ahead, and are often used when it is difficult to see that a traffic light may already be showing red, to warn a driver to prepare to slow down. They may be supplemented with flashing light or lighted sign when light is red or turning red. Some countries also have signs warning of signals for ramp meters, fire stations, and airfields.Warning signs for regulatory signs
As for traffic signals, above, some "stop" or "yield" signs may require additional warning or reminder, especially in dense areas or where the sign has been added recently.Intersections
These signs warn of road crossings at. They may also indicate "hidden driveway" intersecting the road ahead..Lane starts and ends
These signs indicate when a multilane highway is being narrowed, when a passing lane is ending, or where the road is widening or a passing lane starting. Another type of sign is used to indicate central "two-way" left turning lane in center of roadway. Warning signs may also warn of "Highway ends", where the road changes class or type.Merge to stay with through traffic
In the United States and Canada, there is special signage for lanes that are about to exit, so that drivers who wish to remain on the main road have adequate time to merge. Such lanes are sometimes indicated by special striping and the sign, "Through Traffic Merge Left". On freeways, the green directions sign for the exit ramp may have the additional notation, "Exit Only," and should have black letters on a yellow background for emphasis.Roads with one entry point
Roadways that only have one entry/exit point - "dead end", "not a through street" or "no outlet".End of roadway
Signs indicating the end point of a roadway.Pedestrian crossings
These signs are used to warn drivers of people walking in the street. They may also be used to warn of children playing, playgrounds, bicycle area, deaf child, blind pedestrians, and thickly settled zones where pedestrians may enter the road.In California, United States near the Mexican border, there are warning signs showing a running family. This is to warn motorists to look out for illegal immigrants who try to escape authorities by running through freeway traffic. The symbol was created by California Department of Transportation employee John Hood in the late 1980s.