I can already envision it: Google self-driving cars making deliveries.
A self-driving car pulls up and double-parks in front of your building. It texts you to come outside and gives a four-digit pin. You go to the car, type the pin in, and a small door opens with your package sitting there. I guess the car has some weird conveyor system for moving packages into the pickup area.
Is this what you are thinking? I'm not sure how well double-parking by a self-driving car would work (delivery people do it, but they also can use their judgement). The conveyor system also seems like it would create problems.
I'm thinking murtali just didn't think that far.
And conveyors are pretty reliable in industry.