Roads are the biggest limitation on mobility for our older kids, now that we're using walkie-talkies. Anna (5y) can't cross the street on her own, because she is not quite reliable enough at checking for cars. For her, the neighborhood is a collection of islands:

With assistance she can move between them, but otherwise she's pretty limited.

Lily (7y) is better at crossing streets, and we let her cross specific low-traffic intersections. Here they are, in red:

You can see that this opens up the neighborhood dramatically. She can walk to school (reduces conflict when Anna is slow to get ready) and visit friends (~8 of them).

On the other hand, there are still many nearby places they really want to go and can't, because the streets involved are too dangerous. I think the next stage will be learning how to cross at the crosswalk marked below, which opens up the community path, park, and more friends:

Right now we deal with this by just being pretty willing to help them cross that street. It's also possible that some of this will get better with the speed humps they are planning to install in our neighborhood soon.