[max8539]

With a knob, you always could stop what you are doing and look back at the road and then continue. With a touch screen, you need to find a button and touch it without looking at the road, or you need to do it from the start again.

[wvenable]

I have this knob and I don't understand your point. With the knob or the touch screen, you need to look at the screen to see what you're doing. The knob merely controls a cursor.

I find the knob considerably more distracting. First you have translate the motion of the knob to the cursor moving on the screen. Secondly, you have to cycle through all the options so you have to spend even more time looking at the screen. It's significantly faster and less distracting to just reach out and tap the button you want.

Other physical buttons are great but the knob is a terrible UI.

[max8539]

Yes, you still need to look at the screen but could pause this in any position of the selected item and continue after looking back at the road. I was driving an F150 with just a touch screen and it was much worse when I needed to find an item on the screen and try to touch it on a far-located screen in a shaking car.

[wvenable]

In my experience, there is no advantage to pausing on some random icon I don't want. I always have to re-orient anyway. Tapping an icon on the screen is instantaneous. There's also some extra complexity in what grid of icons you currently have selected and how to move between them.

But that advantage goes away for any element that isn't currently on the screen. So navigating between pages or submenus or slide up drawers is much more fiddly than the dial and much more susceptible to the "car shake" issue.