Car behavior isn't one that people have used very often in the past, so I believe it may have been a little neglected as far as features go. It might be worth it to try creating your own car movement from Custom Movement behavior, then you'll have more control over collisions and crashes.
At any rate, I recall that Guyon
recently found a solution to stopping the car on collision, you could ask him about it. I'm not terribly familiar with the behavior myself, and I'm not on my Construct computer at the moment.