Which factors are considered when determining the duration for an all-red clearance?

The duration of an all-red clearance is primarily influenced by the type of vehicular traffic and pedestrian activity at the intersection. This factor is crucial because different types of traffic, whether heavy trucks or light vehicles, have varying stopping distances and acceleration capabilities. Additionally, the volume and behavior of pedestrian activity—such as the presence of crosswalks, the likelihood of pedestrians waiting to cross, and peak pedestrian hours—are also significant.

Understanding these dynamics ensures that the all-red phase is sufficient for all vehicles to clear the intersection and for pedestrians to safely cross without the risk of being in the way of incoming traffic.

While weather conditions and time of day can affect traffic behavior, they do not directly determine the duration required for the all-red phase. Similarly, the location of intersections is a broader contextual factor that may influence overall signal timing but does not specifically dictate the duration of the all-red phase. Lastly, the availability of traffic monitoring systems provides data that can enhance timing effectiveness but does not, in itself, determine clearance duration. Hence, type of vehicular traffic and pedestrian activity remain the core considerations for establishing an appropriate all-red clearance duration.