As the proud owner of a well-used Mini, I feel compelled to weigh in on Ryan Avent's proposal for single-passenger vehicles that don't guzzle so much gas, or use so many materials. He makes a pleasingly contrarian argument that a lot of the problem is government safety regulations, which naturally appeals to me.
All that said, it won't work. First, because you'd be surprised how much room you need for groceries--a full run for the two of us can pack the mini's back pretty easily. And second, it's too dangerous.
It's dangerous enough for motorcycles to share a road with cars, but motorcyles are maneuverable and their riders don't have big blind spots like you do in a regular vehicle. A slightly better-armored golf cart cannot share a road with trucks, which they would have to even in train-accessible suburbs. I am pretty reluctant to drive my Mini on long highway trips, for just this reason.
Differential speeds are a major cause of accidents, as is the inability to accelerate quickly. And of course, even in single-car accidents, lighter vehicles are more dangerous. You're not talking about American auto safety regulations; you're talking about the laws of physics; if you're going to smash into something, you want as much stuff around you as possible to absorb the shock. In a two car accident, the death rate would be enormous, since even my mini could crush one of these things.
Meanwhile, how many people want to park and insure an extra vehicle?
Such a system would be fine in a country where that's all that anyone drove. But that's not the country we live in, and even if we did away with large passenger vehicles, we'd still have to put all the cargo trucks somewhere.