In Maine a lot is left up to the discretion of the Departments Chief. As a volunteer EMT we were allowed one flashing red light on or below dashboard level. One woman complained to the local police, asking "do we have to let them pass?" The officers response was "Why would you not want to?"
The local fire chief was more lenient. VFD members were pretty much allowed to do as the pleased with lights. One member had an old rusted Honda that lit up like a carnival ride (or "Tijuana Taxi" if you will). Strobes added into every existing light fixture on the car. When we make first contact with life from other planets, I've no doubt they'll land in South coastal Maine.
If that's the invisible man at the door, tell him I can't see him!