necessity or not, is it not the drivers responsibility to drive safely and alertly enough to avoid running into the back of someone? i mean, they should have been paying enough attention to see it coming. its not like they just jumped out in front of the other car and they had zero time to react. its on the fuckin freeway for gods sake. you're not supposed to be staring at the ass end of the car in front of you, you are supposed to be looking as far ahead as you possibly can. hitting a parked vehicle IMO is like hitting a building or something. its there, its not moving. you should be able to see that, and maneuver around it.