The most unintelligent thing about my car is .....
I always heard it as "..... the nut holding the steering wheel". ;-)
My wife has a Focus Vignale and its speed limiter system is even more sophisticated than mine. If you drive a Focus, then I’m amazed that you had to ask how the speed limiter would cope with the varying speed limits on your journey into town. Even if you don’t want to use the various driver assist functions, I would have thought that sheer curiosity would have made want to find out how they work. Such an outmoded attitude to the benefits of modern technology surprises me, given your scientific background.