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.^[1]

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 (except for Macau and Hong Kong), 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 (both signs are triangular with a red border). Some countries (like France, Norway and Spain) 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,^[2] most of South America, and also Ireland (diverging from the standards of the rest of Europe) warning signs are black on a yellow background and usually diamond-shaped, while temporary signs (which are typically construction 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 (example); symbolic signs, though long used on certain tradesmen's signs (like the pawnbrokers' tri-ball symbol) 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 signs with embossed letters, 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, 1968 Vienna Convention on Road Signs and Signals (which became effective in 1978) 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 (curves and turns), W10 Series (railroads), et cetera, ending with the W25 Series (concerning extended green traffic lights). 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 (OM Series). In the U.S., Stop and speed limit signs fall under the R Series (Regulatory). 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 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.^[3][4][5] 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

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