No, but you can run a natural experiment: look at towns of similar size (let's say 30k-50k) that had shops downtown and competition from big box stores on the o

No, but you can run a natural experiment: look at towns of similar size (let's say 30k-50k) that had shops downtown and competition from big box stores on the outskirts, but did not block cars from the downtown stores, and see what happened there. Answer: there are a few towns that retained or have regrown a vibrant downtown (I live in one), but not many. Most small cities have a downtown that is either functionally a ghost town, or that has been converted to low-traffic uses (like lawyers' offices). Though not a certainty, it's a pretty fair conclusion that the bricked pedestrian mall is not what killed Richmond's downtown.