Road signs1 of 3
What shape is reserved for stop signs?
The answer
Answer: D. The octagon is reserved for stop signs, and a stop sign means you must come to a complete stop. A triangle means you must yield the right-of-way to cross traffic or to merging traffic, and rectangular signs regulate traffic and direct the driver's speed and direction.
Source: Arizona Driver License Manual — Traffic signs, Regulatory signs (p. 32)