Traffic signs and their specific shapes have special meanings to convey messages to travelers; typically, the more sides a sign has, the more critical the sign is. Each sign is designed so travelers can react quickly on the road to the sign's shape and color.
A circular traffic sign is designated for advanced warning of a railroad. These signs are yellow to get the attention of travelers and notify them that a railroad crosses the roadway ahead.
Another sign used for railroad crossings is the crossbuck sign. This X-shaped sign is only used for railroad crossings. It has a retro-reflective white color with black lettering.
An octagonal sign is always a stop sign and is red in color.
Pentagonal signs represent advance warnings for schools or county route markers. School signs are typically yellow, while county signs are usually blue.
Diamond-shaped signs give travelers warnings about conditions ahead. For example, the signs can signal that curvy roads, divided highways, crosswalks, dead ends and work zones are ahead. Speed bump warnings and low clearance signs are among the other signs that use a diamond warning shape.
Rectangular signs have different meanings depending on whether the sign is horizontal or vertical. A vertical rectangle is used for regulatory signs, such as speed limits, while a horizontal rectangular sign is used for guide signs for expressways and freeways, warning signs for road work, and temporary traffic controls.