If the yellow light is flashing, which vehicles are required to stop?

When a yellow light is flashing, it typically indicates caution and requires specific actions from drivers. In the context of the question, designated vehicles 1 and 2 are the ones that must stop, as they are likely specified in regulations or guidelines concerning the flashing yellow light situation. This could include school buses, certain types of emergency vehicles, or vehicles that are required to follow specific protocols when certain traffic signals are in operation.

Flashers generally ask other vehicles to be vigilant and prepared to stop, but only designated vehicles have the obligation to halt completely. This reflects an important understanding of traffic laws that are put in place for safety, particularly in scenarios involving pedestrians, school zones, or other sensitive areas.

The other options do not align with this requirement, as stopping is not mandated for all vehicles or just specific types without a clear designation, which would lead to unnecessary congestion or confusion on the road. Understanding the specific designations for stopping ensures compliance with traffic laws and enhances safety for all road users.