Zero? I think the expected number of collisions can be larger than zero. Jimmy Johns sandwich delivery by bicycle has resulted in more collisions than zero and that is arguably safe.
replyYou are setting an impossible standard.
I would expect the result to be the same as running into anything else: drone and any payload crash into the ground.
replyDrones are lightweight, they're not going to do much to heavy machinery. Basically the same as a brick wall.
The real fear is propellers hitting a human. The result is not good at all.
Also drone and payload falling to the ground from any kind of height could cause serious injury or death if it falls on someone.
replyWhich is the argument against flying cars. Uncontrolled flying car crashes over populated areas could be catastrophic.
replyEasy, don't walk near buildings then! /s
replyI expect some kind of automatic drone parachute system to develop.
replyI think parachutes take more height to work properly, compared to building heights.
replyMaybe if they fly at much higher altitudes for most of the flight.
They weigh 80-85lbs and travel at speeds of around 50mph.
replyThe impact would be quite serious, if they crash at speed but even falling on a car or a human would be quite serious, possibly deadly, even if the propellers don't spin.