What are the two basic types of overlaps in traffic signal phasing?

The correct answer identifies the two basic types of overlaps in traffic signal phasing as independent and parent/child.

In traffic signal systems, overlaps serve to control additional movement phases while other movements are active, thereby contributing to more efficient traffic flow. Independent overlaps allow a movement to occur concurrently with another movement without being dependent on the status of the other signal phases. For example, a left turn could proceed while the main traffic flow is also moving if timed appropriately.

On the other hand, parent/child overlaps are structured such that the child phase (typically an additional movement like a turn) is dependent on the state of the parent phase (the main traffic movement). This ensures that the child phase can only activate in conjunction with the parent phase, helping to simplify the traffic signal logic and reduce the risk of conflicts between movements.

Understanding these two overlap types is crucial for traffic signal technicians, as it affects how traffic signals should be programmed and managed to improve safety and efficiency on the roads.