Slightly different but related:
I'd like to point out that I've seen increased construction and use of skyways* in more recent times, in downtown city areas near where I live. If the trend continues and spreads, they might become common in urban areas, something to think about.
*"skyway" refers, in this case, to an indoor (covered by a roof and walls with windows) corridor that connects two multi-level city buildings, and connects levels above the ground level, going over streets, so people can walk across from one building to the other while staying indoors and not have to bother crossing a street with traffic.
(I'm afraid I don't have a link or pic handy, sorry. They're also known by other names.)
Heck, I've even seen a few "horizontal elevators (lifts)" in some places as well now.