It is trivially avoided once the kids are old enough, but there's a long period during which kids would be safe enough to roam around in the absence of cars, but aren't in the current environment.

We live a block from the playground, close enough that I can almost see it from our window, but you can't get there without crossing the street. So our kids (7y, 5y) can only go there with a grown up. I've worked on teaching them how to cross the street safely, but they're just not good enough at checking for cars yet.