I think the world needs a more efficient last mile delivery service. Like tubes or something. Guess it wouldn't be so bad if we were fully transitioned to electric vehicles, powered by renewable energy... But that's going to take 20 years at a minimum.
I thought about this for a while, and decided that spherical crates moving through tubes with rollers on the inside--occasionally a powered roller or switch--might work. But then I figured out that a spherical envelope big enough to deliver a decently-large pizza order is likely also capacious enough for a child to try to deliver himself to a friend's house.
And that means the system has to assume that every crate has a kid in it. Or a baby. Or a dog. Or a goldfish. Or a burglar. Or a bomb. Or solid concrete. Or sloshing water. Or a live sample of anthrax. You can't easily idiot-proof it, or guard against intentional acts of malice.
So you might as well go all in, and allow people to deliver themselves through it, by design, as a transit network. Make the spheres 1 m diameter, with a 525 kg gross weight capacity. People can fold themselves up inside one like a Mercury astronaut, if they like. The terminals would look like a cross between a giant bowling ball return and a roller coaster boarding platform. Unmanned crates would likely need some means of disgorging their contents, with the recipient's permission, and then returning to the sender, without direct human intervention.
But wait. That's not wheelchair accessible. So scale up the spheres again, to 2 m diameter, and 4200 kg gross weight capacity, with boarding ramps at every terminal.
It starts sounding really expensive, especially trying to retrofit a city with delivery tubes. Because now someone might want to replace an elevator shaft or two with tubes, and put one delivery terminal in every N floors. I've basically just replaced all the cars and delivery trucks with Wonkavators.
