Drones have the capability of delivering directly to the final destination, unlike railways.
In fact,Amazon could redistribute their inventory between warehouses overnight depending on predicted popularity of various items. Or it allows them to have a gigantic single warehouse with every single item in it, and just worry about distribution centers as opposed to warehouses that hold inventory. Then every hour they could send the packages via drones from their central warehouse to distribution centers where they are immediately put on trucks and sent out.
In fact,Amazon could redistribute their inventory between warehouses overnight depending on predicted popularity of various items. Or it allows them to have a gigantic single warehouse with every single item in it, and just worry about distribution centers as opposed to warehouses that hold inventory. Then every hour they could send the packages via drones from their central warehouse to distribution centers where they are immediately put on trucks and sent out.