A few days ago, in the context of first drone delivery by Google, I asked why don't we build infrastructure (pipes + automatic pods going through them) to deliver grocery-sized packages. Sounds like a literal pipe dream, but I'm not convinced the economics wouldn't work. Deliveries could take a matter of minutes and the network could be expanded at will, starting with a few neighborhood delivery spots. At a price of…
It's been done... operated 1897 to 1953, replaced by auto delivery. https://en.wikipedia.org/wiki/Pneumatic_tube_mail_in_New_Yor...
Specifically, in those systems the pods were moved by compressed air: today they could just be electric and autonomous. They needed to be routed manually at intermediate stations, now they could just reach their destination automatically. Only five pods a minute could travel on those pipes, but electric drive means each pod can keep a minimum distance from the one before. There would be no need for engine rooms with air compressors spaced along the route. Etc.
Basically, you can think of it as autonomous driving on a dedicated road any without obstacles.