I preface my post by saying that I do not drive one of these cars that use touch screens to input car actions. So maybe what I am describing below is already done.

I reject the idea of touch screens for car functions because it takes more than one level of navigation to reach the active button. If the UI designers would change the design so that when the car starts moving the touch screen would change and lock to a display where all driving-related buttons (heating/wipers/car stereo/gears) are close by, highly visible and activated with a single touch I could see myself using a touch screen in a car.

My main reservation is taking my eyes and attention of the road to focus on navigating a touch screen UI put together by 5 teams and 3 different committees.