That sounds like a very painful way to go. Car crashes aren't always fatal, even if done deliberately. If you end up surviving, you'd have very heavy, permanent injuries that make it even more painful to keep on living.
I urge you to seek more peaceful methods in CTBing. You owe it to yourself to pass away peacefully, after all the suffering you've had in your life. Please, think about this. If your goal is to have a successful CTB, you need to ensure that you have little to no chance of survival. Also - you have to consider the peacefulness factor too. Unless, that is, you don't care about pain, and you just want to quickly rid yourself of your own existence. I should also add that impulsive CTBs tend to bear rather adverse results.