Minimum number of signal faces (bulbs) needed for a signal head?

• A. 3
• B. 2
• C. 4
• D. 1

Answer: (A)

Three signal faces are required because each standard color conveys a distinct action and must be visible on its own face. Red tells drivers to stop, yellow signals prepare to stop or clear the intersection, and green means go. If a signal head had fewer than three faces, one of these colors wouldn’t be available to display, leading to confusion and unsafe interpretations for approaching traffic. By using three faces, typically arranged vertically (red at the top, then yellow, then green), the signal clearly communicates the intended state from different angles and distances.