|If driving with your manager is driving you crazy, it is time to put the brakes on this practice. You don't want to drive with him any longer, and he needs to know it right now.|
The best way to approach him is to be honest, open, and kind. Open the discussion by telling him that you are concerned about his driving. You can then mention some specific incidents that were almost accidents, and let him know that you are mentioning this out of concern for him as well as for yourself.
Suggest that you drive to the next few meetings and see how things go from there. In this way, you are not suggesting a long-term change that might be quite threatening to him. This trial approach is far more palatable.
The next step is to be quiet. He may react with appreciation, defensiveness, or even an explanation. But, no matter what he says, have your keys ready for the next ride. You owe this to yourself, as well as to your family, friends, manager, and the company at large.