Hmm, that's interesting.
Well, I've heard native speakers refer to the "quiet street" in the following two situations as "off the main street":
In this one "quiet street" is a continuation of "another street", which is off 5th Avenue.
In this one "quiet street" is off "unnamed street 2" which is off "unnamed street" 1.
This is what I meant by "not directly connected".
What do you think about those two?
What about this one?
Here "quiet street" is off 5th Avenue.
Come to think of it, I now also use "off", because the little street is kind of branching off
. Ok, in this case the off-street directly connects.
Let's say the "quiet street" doesn't connect to Fifth Avenue at all like this
Then the "quiet street" is still off Fifth Avenue, right? No, it's off whatever street it connects to.
Can a street actually be "on" another street? No.
What if we weren't speaking of streets but just lines - would it be correct to say that the thin line is on the thick one in the third figure?
No, it's connected to it.
Prepositions can be so treacherous:-(