Final answer:
A yellow square sign with a stated speed on it is known as a speed limit sign, representing the maximum legal speed for that road section. The displayed speed is the de jure limit, while the de facto limit is the threshold for possible law enforcement action.
Step-by-step explanation:
The yellow sign shaped like a square with a given speed on it is known as a speed limit sign. These signs indicate the maximum legal speed at which vehicles are allowed to travel on a particular stretch of road. In many places, the speed displayed on the sign is the de jure speed limit, meaning the legally enforced speed.
However, the actual, de facto speed limit can be different, as this is the speed at which law enforcement is likely to pull you over. Factors such as visibility, traffic, and weather conditions can also influence drivers' speed regardless of the posted speed limit.
If a vehicle goes over the top at a speed faster than what is indicated on the sign, the driver may be at risk of receiving a traffic citation. Conversely, if a car goes over the top at a speed slower than the posted limit, it could potentially interfere with the flow of traffic, although this is usually less penalized than speeding.