A bit south of SF, the city of San Mateo has kept downtown B street, their main downtown road, closed to all traffic (https://cityofsanmateo.org/4448/B-St-Pedestrian-Mall-Improve...). That area seems just as popular as before. You still park in the same garages.

Note that San Mateo closed off the street to all traffic and turned it into a pedestrian walking/eating area. So it's used for events. Market Street still allows traffic so people can't wander around in it.