It is futile to try to evade the issue of unsafe city streets by attempting to make some other features of a locality, say interior courtyards, or sheltered play spaces, safe instead. By definition again, the streets of a city must do most of the job of handling stangers for this is where strangers come and go. The streets must not only defend the city against predatory strangers, they must protect the many, many peaceable and well-meaning strangers who use them, insuring their safety too as they pass through. Moreover, no normal person can spend his life in some artificial haven, and this includes children. Everyone must use the streets.
-from The Death and Life of Great American Cities, page 35-36.