Being aware of what standard highway signs mean will make you a better driver. If you know what shape of sign you are looking for, you can find it easier in poor visibility conditions. You will also be able to tell what kind of sign is coming up even when it is still quite a distance away.
There are eight different shapes of standard highway markers: octagon, circle, rectangle, diamond, triangle, trapezoid, pentagon and shield-shaped signs.
Standard highway signs fall into six categories: warning, construction, regulatory, service, guide and interest.
Octagon signs indicate "stop"; circle signs indicate railroad crossing warnings and civil defence markers (such as hurricane evacuation routes); a rectangle sign, if standing on end (shorter side at top and bottom) indicate a regulatory marker, and if lying on its sides, it indicates a guide sign; and diamond signs indicate a warning.
Triangle sings, if pointing down, indicate a yield, and if pointing to the side (called a "pennant"), indicate "no passing"; a trapezoid sign (looks like a drawing of a flower pot) indicates a recreational area; a pentagon sign (looks like a child's drawing of a house) indicates a school zone; and a shield sign (looks like a policeman's badge) marks highways and routes.
Colours go hand-in-hand with shapes to pinpoint a sign's meaning. Yellow is for warning; red is for stop or yield, or spells out certain restrictions (such as a "No Parking" sign); green often indicates a guide of some type, such as an exit sign or a mile marker; blue signs are often service signs (pointing to the nearest petrol station, hotel or restaurant); orange means construction ahead.