I don't have any insider knowledge, but if I were writing the FSD system, I'd use the neural network that connects every Tesla back to the Tesla FSD cloud to obtain information about each of the little byways all over the world. I'd get the network to collect information about how previous Teslas have driven down each and every byway, either driven by the driver or by the car, as long as each drive didn't end in a crash. Then, I'd send said information about a particular locality back down to each Tesla that happens to be in that locality. Each car gets advanced knowledge about its own area of operation, but it also gets general information about how to deal with new roads not previously known to the network. If the car can't decide what to do, it gives control back to the driver and records what the driver does and how well that works. Eventually, the network gets so good at driving that it never needs to give control back to the driver. It also knows to avoid little roads that it can't understand. Usually, there's an alternate route.