Which scenario is an example of an authorized emergency vehicle?

An example of an authorized emergency vehicle is a private vehicle of a volunteer firefighter responding to a fire alarm. This scenario is correct because, in many jurisdictions, volunteer firefighters are often permitted to use their personal vehicles to respond to emergencies when they receive an alarm. These vehicles are typically equipped with emergency lights or sirens to alert other road users of their presence and urgency. Consequently, such vehicles are granted certain privileges under traffic laws to facilitate their quick response to emergencies.

In contrast, a regular sedan driving under the speed limit does not fall under the category of an authorized emergency vehicle, as it does not possess any special status or equipment that indicates it is responding to an emergency. Similarly, a delivery vehicle on a scheduled route is also not classified as an emergency vehicle, as its purpose is purely commercial and does not involve responding to emergencies. An off-duty police officer's car parked on the street may not be actively engaged in law enforcement duties, and without its emergency lights or siren being utilized, it wouldn’t be recognized as an authorized emergency vehicle in operation at that moment.