Signs are divided into three basic categories: regulatory, warning and guidance signs. The signs:
- Warn you of hazards ahead that would otherwise be difficult to see;
- Guide you to your destination by clearly identifying the route;
- Regulate traffic speed and movement.
The signs are manufactured in different shapes and colors to convey a particular message.
The background color of traffic signs helps identify the type of information provided:
- Red signs are used to inform the driver of requirements that must be followed and that constitute an Immediatee threat to traffic safety if not followed, e.g. "STOP," "YIELD," "DO NOT ENTER," "WRONG WAY."
- Yellow or Fluorescent yellow-green signs warn drivers of specific road conditions and dangers ahead.
- White signs provide important information regarding traffic regulations that you must obey such as state highway markers, maximum speed limits and other helpful information.
- Orange signs warn drivers of special dangers ahead due to highway construction and maintenance projects.
- Green signs indicate directions, highway exit signs and mileage signs.
- Blue signs impart traveler information to motorists.
- Brown signs indicate nearby parks and recreational areas.
The shape of a sign also gives an indication of the information. There are eight common shapes used:
- Octagonal ("STOP") Sign: The eight-sided red stop sign is a common sign indicating the requirement to stop and yield the right-of-way at an intersection.
- Triangular ("YIELD") Sign: The three-sided red and white yield sign informs the driver that he or she must slow down when approaching an intersection and be prepared to come to a complete stop.
- Square (Regulatory) Sign: The red and white square regulatory signs convey regulations that the driver must follow. Signs indicating prohibitions often will have a symbol inside of a red circle with a red diagonal bar. When you see a red circle with the red diagonal bar it always means "NO."
- Circular (Railroad) Sign: The yellow circular sign is designated to provide information to the driver of an impending railroad crossing.
- Pentagonal (School Zone) Sign: The yellow or the new fluorescent yellow-green five-sided sign indicates the presence of a nearby school and an area in which children will be crossing traveled roads.
- Diamond (Warning) Sign: The four-sided, diamond-shaped signs warn drivers of specific road conditions and dangers ahead. Example shown: Divided Highway Ends
- Pennant-Shaped Sign: The yellow pennant-shaped sign is used exclusively to warn drivers of impending no-passing zones. These pennant-shaped signs are placed on the left-hand side of two-way roads to aid the driver who may be trying to pass a vehicle on the left.
- Rectangular (Regulatory) Sign: In conjunction with pennant-shaped sign you might see a regulatory sign indicating do not pass or pass with care. The white rectangular sign also provides important regulations that drivers must obey, such as maximum speed limits, or contains useful information such as state highway markers.