For2: placard A traffic warning sign is a type of traffic sign that indicates a hazard ahead on the road.

In most countries, they usually take the shape of an equilateral triangle with a white background and a thick red border. However, there are color of the background and the color and thickness of the border varies from country to country.

In the People's Republic of China, warning signs appear with a black border and a yellow background. In Sweden, Serbia, Bosnia and Herzegovina, Croatia, Greece, Finland, Iceland, the Republic of Macedonia and Poland, they have a red border with an amber background. This is due to the weather, as it is easier to see a red/amber sign in the snowy weather than a red/white sign. 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 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, Philippines, and Malaysia 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. Ireland also adopted these standards, diverging from the standards of the rest of Europe. Some other countries also use these standards for some signage.

Image:Signmedian.svg|Diamond shaped with yellow background Image:Highway-Rail_Grade_Crossing_Advance_Warning_sign.svg|Circular with yellow background Image:Advisory_Curve_Speed_English_25.svg|Rectangular shape with yellow background Image:1 1 54.svg|Triangular with orange-yellow background Image:Znak A-30.svg|Triangular with yellow background Image:Zeichen 101.svg|Triangular with white background

History

In 1908 the automobile association in West London set the first warning signs.

Warning signs

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

A general warning signs are used in instances in which the particular hazard, obstacle or condition is not covered by a standard sign. 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 countries using diamond-shaped signs, the explanatory language is written directly on the diamond-shaped sign, although it may contain only a general warning such as "Caution", and a auxiliary signs may also be used. Image:Zeichen 101.svg|Germany caution sign. Image:1 1 54.svg|Sweden caution sign. Image:Znak A-30.svg|Poland caution sign.