How many phases does a three-phase signal provide?

A three-phase signal typically includes three distinct electrical phases that provide a balanced and efficient means of distributing power. This system is often utilized in traffic control because it allows for the coordination of signal timing and traffic flow in multiple directions, especially in scenarios where turns need to be accommodated.

In the context of traffic signals, option B presents a logical interpretation of how a three-phase signal operates. Specifically, it indicates that each of the three phases can represent one of the possible movements at an intersection, which includes the through movements (straight) in both directions and permits a left turn phase. This arrangement allows traffic signals to manage and alternate between these movements effectively, ensuring safety and fluid traffic flow.

The specification of one phase for each axis of travel addresses the need for clarity in traffic signal timing, particularly at busy intersections, where vehicles may need to turn left or proceed straight. This configuration not only helps in reducing the chances of accidents by providing dedicated phases for these movements but also aids in optimizing the use of traffic lights to minimize waiting times.

Balancing this system is crucial for proper intersection function, and understanding it helps in designing more efficient traffic signal systems that cater to different flows of traffic.