Shapes and colors: how to read a sign you have never seen

Road signs in the United States follow one federal rulebook, the Manual on Uniform Traffic Control Devices. Every state adopts it. That is why a sign in Maine and the same sign in Arizona are the same shape, the same color and the same size.

It also means the signs are systematic — and a system can be learned in an evening, while a hundred pictures cannot.

Shape tells you the category

Shape is the strongest signal on the road, because you can read it in fog, in the dark, or from behind snow that covers half the face of the sign.

• Octagon — stop. Nothing else on an American road is an octagon. Ever.
• Upside-down triangle — yield. Also unique.
• Diamond — warning. Something about the road ahead changes: a curve, a merge, a dip, a crossing.
• Pentagon, point up — school zone or school crossing.
• Round — railroad crossing ahead. The round yellow sign with the black RX is the advance warning; the white X-shaped crossbuck stands at the crossing itself.
• Pennant, a long horizontal triangle — no-passing zone. It sits on the left side of the road, which is the giveaway.
• Vertical rectangle — regulatory: what you must or must not do. Speed limit, no turn, one way.
• Horizontal rectangle — guide: distances, directions, route numbers.

Two of these deserve extra attention because the test loves them: the pennant and the pentagon. They are the shapes drivers cannot name even after twenty years behind the wheel.

Color tells you the intent

• Red — prohibition or a mandatory stop: stop, yield, wrong way, do not enter, no turn.
• Yellow — general warning. The road is about to do something.
• Orange — work zone. Same warning, but there are people out there and the fines usually double.
• Fluorescent yellow-green — pedestrians, bicycles, school zones. The brightest color on the road, reserved for the most vulnerable people on it.
• Green — guidance. Where you are, where the exit is, how far.
• Blue — motorist services: food, fuel, lodging, hospitals.
• Brown — parks, recreation and cultural sites.
• White with a black legend — regulatory. Speed limit signs are the everyday example.

Put shape and color together and most signs decode themselves. A diamond you have never seen, in orange, means "warning, work zone ahead" before you have read a single word on it.

The three the test asks about most

The crossbuck. The white X at a railroad crossing carries the legal force of a yield sign. If a train is coming, you stop. Where there is more than one track, a small plate underneath says how many.

The pennant. No-passing zone, mounted on the left. Its partner on the right is the black-and-white regulatory DO NOT PASS sign; the pennant is the advance warning of the same thing.

The pentagon. School zone, in fluorescent yellow-green since the MUTCD adopted that color for schools and pedestrians. When it carries a speed limit, that limit applies during the posted hours and is enforced ruthlessly.

How to practice this

Do not flip through sign flashcards front to back. Go the other way: cover the picture, read the meaning, and name the shape and color it must have. That is the direction the test asks in, and it is the direction that works on a road you have never driven.

Then check yourself against the full chart — shape, color, official name and MUTCD code for every sign that turns up on the written test.