example of an exception - my buddy and I have been working on a route from downtown to his house for 5 years.
There are only a couple of places to cross under a major N/S highway, only a few places to cross a major drainage creek (think LA River), and the choices crossing the last E/W highway are kind of critical, because the 6 blocks south of there is generally the most dangerous riding in town (shopping district).

Think we finally worked it out this year, the bug was crossing the creek and getting us west to safe neighborhoods to cross the last highway.
It's a really nice route, with a significant climb out of the Olmos basin, and we ride by some houses with 3 addresses - but that street gets us west across the 3 main and dangerous n/s thoroughfares, and far enough west to our safe underpass at the highway and right into his neighbornood.