- Less reliance on cars, which results in less parking, which results in less traffic... it becomes self-perpetuating.
- Better walkability
- Knowing your corner store clerk or at least having a rapport with them
- Healthier citizens, due to them walking everywhere (Go to NYC and see how few overweight people you see... not many unless they're tourists. I gained like 10lbs after I moved out of NYC, you get exercise constantly in that city)
- Happier citizens, due to them walking everywhere, things are nearby, their life is more integrated...
etc etc.
I think basically all spaces should be residential / light business mixed. This idea of sprawling suburbs with light business being 10 - 30 minutes away is horrifying and bad for everyone health-wise, time-wise and economically.
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Where I live, the city doesn't really hesitate to shut down sections of roads for festivals, farmer's markets, whatever.
Currently we have a bunch of one ways because all of the restaurants took over half the road for outdoor dining... and honestly, it's pretty nice. The traffic is slightly more congested, but meh... don't drive through the center of the city as a transit option, go around.