I think a good applciation of drones for car safety would be to incorporate drone systems into emergency vehicles. As an example I think of an ambulance that could send a drone further to recognize which roads are more busy, to give the alarm sound so that cars clear the way faster for the ambulance, and even to give a first visual of the emergency situation before the ambulance even gets there. Additionally, ambulance drones have already been used to quickly deliver automated defibrillators to an emergency scene so that care can be applied to the patient before the ambulance arrives. That would be possible also for epinefrine pens or other drugs that need to be administered quickly in life or death situations.
A similar thing could happen with fire trucks. Having a drone which leaves the truck and goes ahead to assess the situation before they get there could save some very valuable time and even give information from a different point of view, helping the fireman response. If this were combined with a drone strong enough to rescue people from tall buildings, that would be amazing.
In the case of police drones are and will continue to be used for surveilance, but specialized drones for catching subjects (maybe with a taser or a net incorporated to them) could be interesting. I've seen racing drones perform incredible acrobatics so it shouldn't be difficult to outrun and reduce a suspect on the run using one of those.