Not a firearms related suggestion, but I would look into taking an evasive driving course.
If you are in a car, then that is your best bet of getting out of a situation. By all means have a firearm up to the job, (I was going to suggest 10mm, 357SIG or the Tokarev: I was beaten to it), I feel that if you have to resort to a gun, then you're already on the back foot.
Using your car as a means of defense with a repertoire of evasive/offensive techniques would possibly give you results without needing to draw
When the right to effective self-defence is denied, that right to self-defence which remains is essentially symbolic.
Freedom: Please enjoy responsibly.
Any idea that relies on murder for its survival in intrinsically weak.