Final answer:
A driver should pull over to allow an emergency vehicle with its siren activated to pass. Understanding the Doppler shift can help determine the vehicle's approach.
Step-by-step explanation:
Upon hearing a siren of an emergency vehicle, a driver must pull over to the side of the road and stop if necessary to allow the emergency vehicle to pass. This is taught as a part of road safety and is critical to ensure that emergency services can reach their destination as quickly as possible without hindrance. An understanding of the Doppler shift can indeed help a driver to determine when an emergency vehicle's siren is getting closer or moving away, which can guide their actions on the road. The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. In practical scenarios, such as the one described, the pitch of the siren would seem higher as the ambulance approaches and lower as it moves away, because of the Doppler shift.