Disclaimer: I am not a lawyer (or a cop) this is not legal advice. My opinion only.
When you are in your car, you are wearing bogu (armor). It is both a help and a hindrance with regard to self-defense.
Some folks have a belief that they are not allowed to intentionally hit someone with their car. While this is normally true, when we're talking about self-defense, it's just another deadly weapon. Like a gun or a knife. It can and will maim and kill other people. However, there is nothing in the self-defense laws that says you can't use it for legal self-defense against a deadly threat (in places and circumstances where deadly force is permitted in self-defense at all, that is).
A car is a dangerous place to be if you are approached by attackers. If a person or people manage to make it to your door, they can keep your door closed quite easily, denying you the ability to escape the vehicle. If they have a gun, well, you have heard the term 'like shooting fish in a barrel,' haven't you? You're the fish, in this case, and your car is the barrel.
If they block your car in, once again, you typically can't easily escape.
Therefore, do not allow this to happen to you.
Remember that your car is armor. It can trap you, but it can also protect you. You can use it as a battering ram. You can use it to escape at high speed.
My personal opinion is this: I would never allow an obviously-angry road-rage type driver to exit his vehicle and step up to my car door with me inside.
Exiting the vehicle puts me in a dangerous situation. Now I am going to have to fight mostly likely and I don't know if he has friends in his car, if he's armed, or if he was actually just planning to steal my car (a common tactic in Detroit, FYI). Staying in my car is equally dangerous, for reasons stated above.
Therefore, I am going to use my car to escape if I can. I will back up at high speed if possible, spin my car around, and drive in the opposite direction at a high rate of speed. What if a cop sees me? I hope a cop DOES see me!
I'll drive up on the curb. I will drive into the oncoming lane (if safely possible). I don't give a dang, this is a life-threatening situation and I am LEAVING.
And if I think I have no other choice to protect my life as well as the lives of anyone who might be in my vehicle, I will drive over the person who is approaching me in a threatening manner. I'll smush him between my car and his, I don't care.
Here's the thought-pattern behind this.
First, he has done something to convince me he's a road-rager and not someone who merely wants to tell me my taillight is out. Maybe he's been cutting me off, swerving at me, following me with his middle finger extended, etc, etc. In any case, I am fully aware of his hostile nature and intent.
Second, he has either followed me as I stopped or he has forced me to stop by cutting me off and slamming on his brakes. He has me cornered.
Third, he has exiting his vehicle and is advancing towards my car in a menacing manner. I don't know what he intends to do, but I am scared (in the legal sense) that he intends to kill me or do me great bodily harm. And it won't be hard to do - he could pull a gun and just murder me right there in the driver's seat, and I could do nothing to stop him. I could get out and run and he could shoot me before I got ten steps away.
Given the circumstances, I am in what the courts call "the reasonable person" description of fear of my life.
That allows me legally to defend myself, even using deadly force. Even before I have seen a gun. The law does not require you to get hit before you hit back. It doesn't require you to get shot at before you shoot back. It requires that a so-called 'reasonable person' would be in legitimate fear of their life. And that definition has been met.
I drop the car into gear, gun it, and escape if I can. Again, if there is no other way for me to leave, I'm going to drive right over that bastich.
Again, I am not a lawyer, this isn't legal advice. Read up on the laws of self-defense and use of deadly force in the location where you are; pay an attorney for advice if you are still unclear. This is my opinion only. But my advice is this - remember that your car is a weapon, and a legitimate one to use if you must in a self-defense situation.