An alternative & arguably easier setup is using the Park & Ride option in NAM's Traffic Simulator Configuration Tool. It forces the sims to find an actual parking facility if they want to travel to work by car, the ones "included" in commercial and industrial growables don't count, only the ones you plop yourself, so a town without parking facilities and neighbor connections by road will be completely car-free (excluding the ones that spawn from civic lots of course).
It'll also enable you to make the center of a city virtually car-free by placing all parking facilities and high capacity roads outside of it and making extensive use of basic streets, busses, light rail transit, subways and ped malls in the center, similar to a lot of cities in Europe and the Taiheiyo Belt.
