Final answer:
At the crest of a hill, be prepared to slow down and yield to oncoming traffic for safety. Stay alert for pedestrians, and be aware of the actual frequency of emergency vehicle sirens, indicating it's time to yield. Traffic signals also regulate vehicle speeds and help pedestrian crossings.
Step-by-step explanation:
At the crest of a hill, you should always be prepared to slow down and yield to oncoming traffic. This is crucial for maintaining safety on hilly roads where visibility is limited. When approaching the crest of a hill, drivers may not be able to see vehicles coming from the other direction, pedestrians, or obstacles in the roadway. Slowing down enables you to react promptly to unexpected situations. Additionally, yielding to oncoming traffic is important because the path of both vehicles intersects, creating a potential for collisions if the right-of-way is not respected.
Furthermore, it is imperative to be ready for scenarios such as pedestrians crossing, emergency vehicles passing by, or the necessity to stop. When you encounter an ambulance with its siren blaring, the sound's frequency you observe will most closely match the actual siren's frequency when it is in front of you, due to the Doppler effect.
Road safety measures like traffic signals also play a significant role in controlling vehicle speeds and ensuring pedestrian safety, as they enforce drivers to stop at intersections and allow pedestrians to cross at designated times.