I think it is uncontroversial that touchscreens do (can do, on some models do, ...) more things than physical buttons could, without having so many buttons as to be un-navigatable.<p>Maybe the solution would be:<p>1) physical buttons for the most common and critical while-driving tasks<p>2) Physical buttons with little screens showing context dependent meanings, aligned on the side of a big screen, for quick selections beyond (1).<p>The button screens do most the work of providing options-for-current-context, with the screen adding more helpful context.<p>3) Touch buttons on screen for unimportant but high-option tasks, such as selecting a song, album or artist. Or changing settings that largely keep stable values.<p>In other words, get the most out of every mode. Maximize the utility of physical buttons with the de-cluttering effect of a touch screen.