You could make them like these soaring vultures and put them over every intersection. You could even tether them so that they're powered and then you just have them, circle around and monitors situations.
Or if they were untethered when an accident happens the drone could go and over say 300 or 400 feet around the incident so that if it were to fall it wouldn't fall on top of the scene but you could still get a relatively instant information about what's going on and who's involved.
