Please help! Reoccurring nightmare affecting my day to day life?

Dreams do not predict the future. I want you to know that. They are only a convenient window into the inside of your mind. It probably just represents a lingering fear of car accidents, which probably has some root in your judgment of your proneness to a car accident. It never happens due to your failure, only the aspects you can't control and you hate thinking that even though you drive well, you are still at risk. If not this then my next best guess is that you are just a nervous driver and the dreams come from that.