Traffic warning sign

[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 (excluding Macau and Hong Kong) and North Korea, they appear with a black border and a yellow background.

In Sweden, Greece, Finland, Iceland, Poland, Cuba, Nigeria, South Korea and Vietnam, they have a red border with an amber background.

In the United States, Canada, Mexico, Australia, Japan, Liberia, Sri Lanka, New Zealand,[2] most of Central and South America, some countries of Southeast Asia, 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.

In 1909, nine European governments agreed on the use of four pictorial symbols, indicating bump, curve, intersection, and railroad crossing.

As the 20th century progressed, and traffic volume and vehicle speeds increased, so did the importance of road sign visibility.

Flat metal signs reappeared in the 1980s with the widespread use of surfaces covered with retroflective sheeting materials like Scotchlite.

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.

Some jurisdictions have criminalized unauthorized possession of road signs or have outlawed their resale to scrap metal dealers.

[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.

Warning signs can indicate any potential hazard, obstacle or condition requiring special attention.

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.

Steep hills may also feature "Runaway truck escape" or "Emergency stop" areas with corresponding signs.

Another type of sign is used to indicate central "two-way" left turning lane in center of roadway.

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.

In California, United States near the Mexican border, there were warning signs showing a running family.

(Note that some "high water" signs are posted to alert drivers of a flood-prone area and do not actually mean that there is a flooded section of road ahead.)

Some countries also have signs warning of signals for ramp meters, fire stations, and airfields.

These signs may be used to warn people of oncoming traffic; shown when a motorway becomes a dual carriageway or a normal road without a central reservation or median.

In the United States the warning of all types of railway crossings is made using a circular yellow sign.

Flying socks, as indicated in Poland by a windsock on red triangle or yellow diamond signs, indicate locations where a strong side wind may cause the trajectory of the moving vehicle to change drastically, perhaps even "flying" across lanes, causing an accident.

These signs warn of approach to where firefighters may be entering the road with fire engines or other emergency apparatus, where other drivers will have to stop and wait until they pass.