"One of the biggest benefits of Sat Navs IMHO, is that they tend to concentrate all the traffic onto trunk roads, thus leaving the secondary routes nice and clear for those of us fortunate enough to be able to read a map. It's an ill wind as the old saying goes....."
One of the big problems in the cities here (especially in Southern California) is that the routing programs are now monitoring live traffic conditions, to the second. The freeways will tend to be completely clogged, taking hours to get anywhere.
So the programs are now routing rush-hour traffic through little neighborhood streets, some of them MILES out of the way. So if a freeway jam means that it will take two hours to get from Rancho Cucamonga to downtown Los Angeles, but only an hour and a half through an obscure network of neighborhood streets, the satnav will route all its cars THAT way. So now, village streets miles from the freeway are ALSO clogged with cars, making it difficult for people to even get out of their driveways, much less walk the dog ...
I don't live in that world, but that's what friends who DO live there tell me .....