Final answer:
When you see an emergency vehicle with flashing lights and a siren, you should immediately pull over to the side of the road and stop to allow the vehicle to pass.
Step-by-step explanation:
When encountering an emergency vehicle with flashing lights and siren, the appropriate action is to pull over to the side of the road and stop. This allows the emergency vehicle to pass by quickly and safely, ensuring that it can get to where it is needed as soon as possible.
Other actions, such as ignoring the emergency vehicle, continuing at the same speed, or increasing your speed, can obstruct the emergency vehicle and are against traffic laws. Remember, the Doppler effect can help in identifying when an ambulance is approaching or moving away from you, but regardless, you should always pull over and stop when you see flashing lights and hear sirens.