I've been to Oxford a few times and never found it much worse than any other city to drive round so I'm not sure what problem they're trying to solve.
The trouble with these sorts of ideas is that the law of unintended consequences comes into play. People don't behave as a homogenous whole so trying to form a scheme to control where people do and don't go is, at best, odd behaviour and, at worst, insane. It's why mass transportation systems struggle to work compared to individuals owning a car. Admittedly I don't live anywhere near a city (thank $deity) but I can't imagine a single journey I do that would be feasible using a bus or train. I'm either carrying my own bodyweight in stuff with me or I'm doing unique journeys at odd times.