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There’s plenty wrong with turn-by-turn navigation, so here’s a completely different solution: boil the route down into the most simple set of rules possible, and leave the user to it.
There are plenty of systems that can be described far more simply than they initially appear — and directions are one of them. So instead of just describing which left and right to take based on distances travelled, an algorithm could boil down instructions to a simple set of logical rules which can be used to navigate to the same destination. If nothing else, it’d keep you mentally alert during the journey. [XKCD]
Of course, in reality this is stupid, since it requires you to know the name of the streets and highways in advance. If you knew the road layout that well already, why would you need to ask directions?
Surely you’d simply read the street signs as you went and only turn in the absence of presidents or prime numbers?
Of course the hours spent memorising the all the (presumably US)presidents and prime numbers up to a thousand might be better spent purchasing a tomtom.
Plus this really relates to America and Americans memorising anything is worthy of it’s own joke