Sign shapes and colours

A sign you have never seen before is still readable, because three things carry meaning independently: its shape, its colour, and the message printed on it. Get the first two right and you can usually act correctly before you finish reading the words.

Shapes worth knowing on sight:

• Octagon — stop.
• Downward-pointing triangle — yield the right-of-way.
• Diamond — a warning about what is ahead.
• X-shape at a track — railway crossing.
• Circle with a slash — the action shown is not permitted; a plain green circle means it is permitted.

Colours carry a second layer. Yellow warns of a hazard ahead. Orange means construction or maintenance work. Green gives distance and direction. Blue points to motorist services such as fuel or a hospital. Fluorescent yellow-green is reserved for school and school crosswalk signs, so it stands out from ordinary warnings.

Red is the one to read carefully rather than quickly: it appears on both the stop sign and on prohibition signs, and in both cases it is telling you what you may not do.