n this particular regard kb, I just don't understand your argument.

'K. Walk with me:

1) Cars operate in a two-dimensional environment constrained by roads and traffic laws. Additionally, motor vehicle traffic is heavily constrained such that motion vectors of any adjacent vehicles are identical: like traffic moves at like velocity in identical direction.

2) Aircraft operate in a three-dimensional environment constrained by flight corridors and traffic laws. Additionally, air traffic is heavily constrained such that vehicles with disparate vectors are separated by nautical miles of distance. Finally, airspace over populated areas tends to be heavily restricted.

So yes: accidents can happen with cars... but the odds of any given trip to the grocery store ending in a fireball are slim indeed. General aviation, on the other hand...

Private-flight crashes were 12 times higher than the average rate for other types of general-aviation flying, Demko said.

The rate of deadly wrecks in such private flying has grown faster than accidents as a whole, up 25 percent since 2000, Earl Weener, an NTSB board member, said in an interview before the forum. About 1,500 people have died on general-aviation flights since the crash by Pinnacle Airlines Corp. (PNCLQ)’s Colgan, Weener said.

So it comes down to statistics and manageable risk. UPS, for example, delivers 16 million packages a day with 93,000 motor vehicles. For those sixteen million packages, UPS averages less than one accident per million miles driven.

Now - let's assume that a UPS drone is 100% as safe as a UPS truck. Not likely in my opinion (we'll get into that in a minute), but let's presume. The problem being a UPS drone won't be able to deliver as many packages as a UPS truck for the simple fact that UPS drones won't look like this:

So let's ignore for a minute the fact that there will be many packages a drone can't deliver. Let's ignore for a minute the fact that anything reliant on GPS is relying on a minimum accuracy of 6 feet and a median accuracy of 30 to 40 feet. Let's ignore the fact that you can put a UPS truck out in the morning and bring it in in the evening, all packages delivered. Presume you've got ten drones replacing one UPS truck.

Your accident rate just went up by a factor of ten.

The other immediate, glaring problem is that "things that fly" experience different traffic incidents than "things that drive." A UPS truck can have a fender-bender. A hexacopter with an iPad isn't going to "bump into" something - it's going to collide and convert its rather sharp rotating mass into kinetic impact. And granted - it won't collide with the same kinetic energy as a UH-60 slamming into a housing development... but it will collide with enough kinetic energy to get the editorials churning.

Then there's the "delivery" aspect of it. Consider: getting that iPad onto someone's porch is the technological equivalent of getting an AGM-65 into a Toyota. And in order for the CIA to get an AGM-65 into a Toyota, we had to generate LIDAR for all of the Hindu Kush, triangulate via special forces and coordinate with airborne and satellite-borne reconnaissance. GPS for military is unlocked; they have half-inch accuracy. Meanwhile dGPS for civilian use will get you within six feet if everything's perfect; most municipality GIS databases are off by 50 feet or more.

Amazon also cares a bit more about budget than the CIA does. And in the end, it's still a person driving the thing.

From a pragmatic standpoint, it makes more sense for Amazon (or Taco Bell, or anybody) to deliver your shit via bike messenger than it does by drone. Bikes have brakes. They can loiter without consuming resources. They don't need a power-to-weight ratio greater than one. And if you're tying up an employee to deliver your package anyway, might as well tie him up with the package, rather than driving a flying moon rover across Manhattan to bring you an iPad while dealing with everyone else's UAVs in a mad attempt to not clip a pigeon and spiral down on a bus stop with 30 lbs of lithium-ion powered carbon fiber.

Here's my argument: I know quad copters and even the ones capable of 10g payloads hurt like a mutherfucker when they hit you in the face. And they hit you in the face a lot. And while the technology may well advance in a direction to keep them from hitting you in the face to the point where it makes sense to throw an iPad on a Hexacopter to get it to your apartment ten minutes faster, the technology is likely to advance even further in far more pragmatic, far less dangerous, far less catastrophe-prone directions.