There are two concrete, real examples, of a routing UX that anyone can just try out - just grab an android phone or an iphone and directly copy the experience. Just sit down and try the most basic goal of using a nav system - enter and address and start and do it on your car system and on either phone.
Oh, wait, differing goals. I, as a user, want a usable system. The maker of these awful nav systems have an entirely different goal. They are trying to sell an "option" upgrade to car makers who then include it in "option packages" with the car... usability is way way down the list after bells/whistles/marketing/subscription sales