when I was learning to drive I was going down hill on a dirt road and the car shut off and it wouldn't get the brakes, I panicked and put in in reverse and than on park, the car made all sorts of noises and it finally stopped, after having a mechanic check the car I ended up bending some kind of pin that was part of the tranny and it was replaced. so i guess some cars do have some kind of safety feature to prevent this :dunno: