Sometimes you need to call the council or the road authority for your state, not to report them, but to find out what the law is regarding how they are parked. Nothing worse than being wrong when approaching a neighbour, as they may have every right to be there (doubt it, but it pays to check).

Frankly though, if there is even the slightest concern that an emergency vehicle would not be able to make it up the street due to how they are parked, then the authorities need to be notified. Lived in street with bad parking and an ill husband, it was always a stress if we had to call an ambulance at night.