Using the standard dual-ring phase numbering convention, which two phases could be displayed simultaneously?

Using the standard dual-ring phase numbering convention, phases that are displayed simultaneously must be spaced such that they do not conflict with the operational needs of the signalized intersection.

The dual-ring system organizes phases into two rings. Phases in the same ring cannot operate at the same time due to their sequential nature. For instance, phases 1, 2, 3, and 4 typically represent one ring, while phases 5, 6, 7, and 8 represent the other ring.

When considering the choice of phases 1 and 5, these phases are from different rings of the system, allowing them to be displayed simultaneously. Phases 1 and 5 can operate concurrently because they are on opposite sides of the dual-ring system, which prevents any conflict in their operation.

This ability to operate different phases simultaneously without conflict is a vital feature of the dual-ring design, as it maximizes efficiency and safety at intersections. Other combinations presented in the options group phases from the same ring or cause operational conflicts, making them unsuitable for simultaneous display.