Question

You must yield for police cars, fire engines and ambulance vehicles _______.

1) never
2) when you see a flashing red or blue light or hear a siren
3) only when other vehicles yield
4) none of the above

Answer 1

You must yield for emergency vehicles when you see flashing lights or hear a siren, as it's vital for the safety and efficiency of their response. The observed frequency of a siren matches its actual frequency when the ambulance is directly in front of you, and the Doppler effect causes pitch changes as the emergency vehicle moves closer or further away.

Step-by-step explanation:

You must yield for police cars, fire engines, and ambulance vehicles when you see a flashing red or blue light or hear a siren. This requirement ensures the safety of both the emergency responders and all other road users. It also allows emergency vehicles to reach their destinations as quickly as possible, which could be crucial in a life-threatening situation.

Regarding the GRASP CHECK, the frequency you observe most closely matches the actual frequency of the siren when the ambulance is directly in front of you. When it is coming towards you or going away from you, the frequency changes due to the Doppler effect, which causes a shift in the pitch of the sound as the source of the sound moves relative to the observer.

Lastly, the pitch of a siren will change as an ambulance drives around a park with a circular road. As the ambulance moves closer to you, the pitch will be higher due to the compression of sound waves. As it moves away, the pitch will lower due to the stretching of sound waves.