Regulatory Signs
Regulatory Signs
Regulatory signs tell you what the law requires, prohibits, or limits. On the Guam written test, expect questions that separate a legal command from a warning, and that test whether you can read a sign’s color, shape, and plaque together. Guam follows the national MUTCD system, so the meanings below apply on Marine Corps Drive, Route 1, and local roads alike.
Core rules
- Most regulatory signs use a white background with a black legend; red is reserved for prohibitions and for STOP/YIELD.
- STOP is the only octagonal sign. YIELD is the only downward-pointing triangle. Both require you to give way; YIELD does not require a full stop unless traffic, a stop line, or a sign makes it necessary.
- A red circle with a diagonal slash means “do not.” A left-turn arrow under that symbol prohibits left turns; a time plaque such as “7–9 AM” limits the prohibition to those hours.
- Speed limit signs are white rectangles with black numerals. The number is the maximum for normal conditions, not a target. Lower speeds are required in rain, fog, or heavy traffic.
- Lane-use signs and pavement arrows can require a turn; a white arrow in a white-background sign is regulatory, not a suggestion.
- Parking signs are literal: “No Parking” allows stopping briefly to load or unload where safe; “No Stopping” forbids stopping at all.
Worked example
You approach an intersection and see a white rectangular sign with a black left-turn arrow crossed by a red circle and slash, with a plaque reading “7–9 AM MON–FRI.” At 8 AM on Tuesday, the sign prohibits a left turn. At 10 AM, the same sign does not prohibit the turn, but you still must obey the traffic signal, yield to pedestrians, and turn only from the proper lane. At 8 AM on Saturday, the time plaque is not active.
Traps that cost marks
Do not treat every yellow sign as a law; yellow warns. Do not read a prohibition plaque as applying all day when it lists hours. Do not assume a green light cancels a “No Turn on Red” sign. Do not confuse “No Parking” with “No Stopping.” Finally, a posted speed limit is not permission to drive that speed when conditions are poor.