It's important to be able to immediately understand the information posted on placards along streets or highways.
The color of road indicators signifies what type of information they contain. For example, warning signs have a yellow background with black lettering or symbols. The shape of a placard also conveys information. Most warning signs have a diamond shape for easy and quick recognition. However, there are exceptions, such as the rectangular sharp bend in the road indicator and the pennant-shaped No Passing Zone placard.
They are strategically placed for your protection as well as the protection of others, warning drivers of approaching conditions that may be dangerous. They are there for a reason and are therefore important to heed.