A somewhat related question....
For those of you who have had experience riding in ambulances, what does it mean when the lights are on but the sirens are not? I heard it means that the patient in the ambulance is deceased and they are transporting them to the hospital, but also that as long a the sirens are not on, it doesnt mean anything - could just be paramedics trying to get through traffic. Any truth to this?
Running with lights and siren is called, "Code" or "Upgraded" and lights only is often referred to as "Downgraded", no lights and sirens is usually referred to as "No-code" Many (mostly law enforcement) refer to driving like a banshee with no lights and siren as "Stealth Mode." The slang term used for running L&S is "running hot."
Getting to your question. It varies on protocol for each state, region, or medical director. But, in general I usually drove with lights only to a scene at night when I didn't want to wake people up as I drove by their houses. Mostly, because there isn't much traffic at 2AM and so, it's not worth waking up people to get to a nursing home for a person that fell and hurt her hip last week.
I also rode lights only on highways and interstates quite alot. The reason here is quite simple: The dang siren gets annoying after about 5 minutes, it'd drive you crazy. Once, I left it one for a 2 hour drive because traffic was bad and the thing overheated and shorted out (It was pretty hilarious sounding when it was overheating
😀 ) Eventually, I got to the point where I'd drive "No-code" on the highway except when there was heavy traffic or I really needed to get somewhere. It turns out this is usually safer because people do really stupid things when they see the lights and sirens (another tale for another time).
Ambulances drive no code when they have a patient that is either stable or dead, so they shouldn't have lights on at all. There is no justification in this case for putting lives in danger (Yes, as I alluded to earlier, driving with Lights and sirens is dangerous). Sometimes, on long transports, they will go code or downgraded also.
Anytime you see lights or sirens, you should yield. If the lights are on, it's for a reason.
Edit: One more time, when you use lights only is when you are backing up an emergency vehicle (that may just be a state law though).