Do not walk lights typically begin flashing how many seconds before the green signal turns yellow?

The correct duration for when do not walk lights typically begin flashing is 15-30 seconds before the green signal turns yellow. This time frame is crucial for ensuring pedestrian safety. The flashing do not walk signal serves as a clear warning to pedestrians that they should not begin to cross the intersection, as the light will soon change.

From a safety standpoint, this advance warning allows pedestrians to clear the crosswalk if they are already crossing, or gives those waiting at the curb a signal that they should not enter the crosswalk. This timing helps to reduce potential accidents between pedestrians and vehicles that will soon be entering the intersection as the light changes.

The other options suggesting longer or significantly shorter durations do not align with standard traffic signal operations and regulations, which maintain a balance between allowing enough time for pedestrian and vehicle movements while ensuring overall traffic flow. Thus, the 15-30 second range effectively meets the needs of traffic safety protocols.