Any solution to self-driving cars (that purports to be a universal solution) that requires specific modifications to the roads is doomed to failure. Even leavi

Any solution to self-driving cars (that purports to be a universal solution) that requires specific modifications to the roads is doomed to failure. Even leaving aside all the gravel and dirt roads, and the many places where, at any given time, there's construction moving a lane 5 to 15 feet to one side temporarily, do you know how many miles of road there are in the US alone? I sure don't, but I know it's a staggering amount, a hell of a lot of it is rural (and some seasonal), and getting all of it retrofitted with even the most simple and low-tech self-driving guidance assist tech like your magnetic nails would cost vast amounts of money and either take a decade or three or cost about ten times as much.