Amazon should build some narrow ones.
https://en.wikipedia.org/wiki/London_Post_Office_Railway
Here are cool mail rail photos from some urban spelunkers:
http://www.placehacking.co.uk/2011/04/24/security-breach-lon...
http://untappedcities.com/2013/03/15/nycs-pneumatic-tube-mai...
I was going to say the destruction of it was spearheaded by the automobile companies, but I was confusing that with the fate of the streetcar system in NYC and elsewhere:
http://en.wikipedia.org/wiki/General_Motors_streetcar_conspi...
They could sling a package across Manhattan in minutes, but to drive there, then as now, takes a lot longer.
I'm not sure about narrower though -- maybe the "with car" design could be modified to have shipping containers placed on to the sleds?