I don't understand the question. Maybe I just am missing something.
How is a gun going to be helpful if one's car breaks down? Don't get me wrong, I can see how having a gun in the car on your person can prove useful in general, it's why I have a CHL, after all. What I don't quite get is, how it would prove useful specifically if your car craps out? My previous car crapped out on me on two occasions, and on neither of these occasions do I recall thinking, "I sure wish I had a gun in the car."
Are we talking like, you're driving down some desolate, unpaved wilderness road with no one around for hundreds of miles, the car fails, and you need a gun for survival?