Ooh, I didn't even think about hackers. Was thinking more about reliability. One way to do it is to make roads for automated cars only and have them all communicate with each other and a central router. Peds and cyclists would need a separate routing system. Even then, hackers become a problem.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"