What happens when vehicles pass each other while traveling in opposite directions?

When vehicles pass each other while traveling in opposite directions, the scenario involves maintaining safety and following traffic regulations to prevent accidents. The correct choice indicates that vehicles can pass when it is safe. This means that drivers must assess the road conditions, visibility, and the behavior of the other vehicle.

Safe passing involves ensuring that there is enough space to do so without encroaching on the other vehicle's lane. It also requires observing road signs and markings that may indicate designated passing zones. When both vehicles are aware of their surroundings, the exercise of passing safely minimizes the risk of collisions, making it an essential aspect of driving etiquette and traffic safety.

The other choices represent incorrect directives that do not align with standard driving practices. For instance, the notion that vehicles must stop unnecessarily impedes traffic flow and is not practical in most scenarios. Saying vehicles may pass only when signaled lacks the consideration for independent judgment drivers must take while on the road. Similarly, the idea that vehicles are required to maintain speed does not account for the need to adapt to changing conditions, such as the presence of oncoming traffic or roadway obstacles.