...ambulance, or fire engine or police? The law states you must pull as far over to the side to make way for emergency vehicles, and I see emergency vehicles waiting constantly for ignorant people to move, and they never do.
People don't move over probably because they're pre-occupied with loud music going on with closed windows. maybe they have no room to move. Ya some could also be jerks...as long as your vehicle is not impeding their path, you'll be fine. Usually this means staying close to the side of the road as possible whether it be the shoulder side or median side. I notice that emergency vehicles like to "part waters" by going between lanes of cars. Better chance of getting through, I suppose.