There appear to be some hidden presumptions here, including in my own post: Are you in the car, or out of it?
Is the car moving, or stopped? Can you move the car?
What direction is the attack coming from - front, rear, drivers side, passenger side?
Can you drive out of the kill zone, or are you truly blocked in? Could you get out by driving on the sidewalk?
And most important:
Are you the target of a dedicated attack, or just blocking someone's escape?
All of them change the potential answers. First, as always, we must define our terms and frame of reference.