What is the role of a yellow change interval in a traffic signal phase?

The role of a yellow change interval in a traffic signal phase is primarily to signal the end of the green light. During this phase, the yellow light serves as a warning indicator that the signal is about to change to red. This alerts drivers that they need to prepare to stop if they can do so safely. The yellow interval is crucial for promoting safety at intersections, as it helps to reduce the likelihood of accidents caused by sudden stops when approaching a traffic signal.

While it might seem that a yellow light could allow for other functions, such as giving extra time for vehicles to accelerate or to enable emergency vehicle passage, its main purpose is to provide clear communication to drivers about the impending change in signal state. This creates an opportunity for drivers either to stop in a controlled manner or, if they are already very close to the intersection, to proceed through the intersection safely before the light turns red.